RESEARCH ARTICLE Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 1 of 22 Mudstone diagenesis and sandstone provenance in an Upper Jurassic – Lower Cretaceous evolving half-graben system, Wollaston Forland, North-East Greenland Mette Olivarius1 , Afsoon M. Kazerouni2 , Rikke Weibel1 , Thomas F. Kokfelt3 , Jussi Hovikoski4,5 1Department for Geo-energy and Storage, Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark; 2Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark; 3Department for Mapping and Mineral Resources, Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark; 4Department for Geophysics and Sedimentary Basins, Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark; 5Geological Survey of Finland (GTK), Espoo, Finland Abstract The influence of rifting on the composition of Kimmeridgian to Barremian mudstones from northern Wollaston Forland, North-East Greenland is investigated by petrographic and mineralogical analyses of the Brorson Halvø-1 and Rødryg gen-1 cores, and provenance analysis by zircon U-Pb age dating of nearby sandstones. Mudstone composition varies systematically as a function of the timing of rifting progression and position in the half-graben depositional system. Pyrite primarily precipitated in the early rift to rift climax phases. Euhedral pyrite overgrowths on framboids formed only during the rift climax phase (Lindemans Bugt Formation). Dolomite is the dominant carbonate cement, except for the sediments deposited in the early waning rift phase (Palnatokes Bjerg Formation) where calcite is dominant, and in the late waning rift phase (Stratumbjerg Formation) where siderite dominates. The highest-temperature reactions with precipitation of illite, quartz, ankerite and barite signify sediment burial depths of >2 km prior to exhumation. Uplift-induced fracturing occurred mainly in the early rift to rift acceleration succession (Bernbjerg Formation). Mudstones in the proximal part of the half-gra- ben (Rødryggen-1) include more detrital kaolinite than the distal mudstones (Brorson Halvø-1), which contain more mixed-layer illite-smectite and illite. Vermiculite was deposited only in the proximal part of the basin in the rift climax and waning rift successions. Chlorite was deposited proximally and distally during the waning rift phase, though supply began earlier in the distal part. Fine-grained sediment in the distal part of the half-graben was therefore probably supplied by axial transport from Palaeoproterozoic crystalline rocks and Meso- to Neoproterozoic metamorphic rocks located to the north and north-west. This agrees with the zircon provenance signature from outcropping sand-rich facies, where zircon grains with U-Pb ages of 2.0–1.6 Ga are dominant, in addition to common 1.6–0.9 Ga ages, and fewer 2.8–2.6 Ga and 0.47–0.36 Ga ages. *Correspondence: mol@geus.dk Received: 03 Jan 2022 Revised: 03 Oct 2023 Accepted: 03 Oct 2023 Published: 21 Dec 2023 Keywords: diagenetic processes, mudstone mineralogy, petrography, provenance analysis, rifting Abbreviations: BSE: backscattered electrons EDS: energy dispersive X-ray spectrometry GEUS: Geological Survey of Denmark and Greenland K-S: Kolmogorov-Smirnov LA-ICP-MS: laser ablation inductively coupled plasma mass spectroscopy MDS: multidimensional scaling SE: secondary electrons SEM: scanning electron microscopy TOC: total organic carbon XRD: X-ray diffraction GEUS Bulletin (eISSN: 2597-2154) is an open access, peer-reviewed journal published by the Geological Survey of Denmark and Greenland (GEUS). This article is distributed under a CC-BY 4.0 licence, permitting free redistribution, and reproduction for any purpose, even commercial, provided proper citation of the original work. Author(s) retain copyright. Edited by: Jon Ineson & Jørgen Bojesen- Koefoed (GEUS, Denmark) Reviewed by: Chris L. Kirkland (Curtin University, Australia), Kevin Taylor (The University of Manchester, UK) Funding: See page 20 Competing interests: See page 20 Additional files: See page 20 1. Introduction The archetypal half-graben setting has an ample sediment supply and can be divided into several sedimentation zones related to proximity to bounding faults and rift evolution (Surlyk 1978; Gawthorpe & Leeder 2000). This sub- division contributes to evaluations of sediment distribution in basins. More- over, when knowledge of structural evolution is combined with information on basement rocks in a hinterland area and sediment delivery systems, changes in sediment composition can be linked to source changes over time. Possible trends in sediment composition are not well-known in distal marine half-grabens that may be largely isolated from coarse-grained clas- tic input by coast-parallel submarine rift shoulders. Such a setting results in axial sediment transport and mudstone deposition, particularly in basins detached from the coastal area. Therefore, the Rødryggen-1 and Brorson Halvø-1 cores from northern Wollaston Forland in North-East Greenland (Fig.  1) were used in this study to investigate the proximal versus distal development of a mudstone-dominated half-graben succession deposited during Late Jurassic to Early Cretaceous rifting. Organic-rich black shales https://doi.org/10.34194/geusb.v55.8309 https://orcid.org/0000-0003-3853-7543 https://orcid.org/0000-0002-8155-8879 https://orcid.org/0000-0001-6311-2593 https://orcid.org/0000-0003-1941-920X https://orcid.org/0000-0001-6330-8713 mailto:mol@geus.dk https://creativecommons.org/licenses/by/4.0/deed.ast Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 2 of 22 GEUSBULLETIN.ORG have accumulated in many contemporaneous basins, especially in the northern hemisphere (Langrock et al. 2003; Mutterlose et al. 2003; Rogov et al. 2020), so the findings of this study facilitate the prediction of mud- stone composition in such basins. The Rødryggen-1 and Brorson Halvø-1 boreholes were drilled in 2009–2010 to depths of 234.5 and 225.7 m, respectively, covering Kimmeridgian to Barre- mian sediments (Fig. 2) that represent prolonged mud- stone deposition in an evolving half-graben setting. The studied half-graben was bounded by north–south-orien- tated fault crests delimiting this basin from the rest of the rift system and from the palaeo-coast to the west (Surlyk 1978). Late Jurassic – Early Cretaceous rifting was widespread along the Norwegian–Greenland Seaway, which connected the proto-Arctic to the proto-North Atlantic (e.g. Stoker et al. 2017). We aim to address two main research questions in this study: (1) How do the different phases of half- graben development (i.e. early rift, rift acceleration, rift climax, waning rift) affect the composition of the depos- ited sediment in a mudstone-dominated environment? (2) To what extent does the sediment composition dif- fer between the two cores that represent the proximal versus distal parts of the half-graben system? 2. Geological setting The Greenlandic craton consists mainly of crystalline base- ment, which is exposed at the rim of the Greenland ice sheet and in tectonic windows in the Caledonides (Fig. 1; Henriksen et al. 2008; Kalsbeek et al. 2008a). The sediment source areas relevant for this study are present within the East Greenland Caledonian fold belt, which originated from the Laurentia–Baltica continental collision that took place in late Cambrian to early Devonian time (McKerrow et al. 2000; Smith & Rasmussen 2008). The orogenesis caused westwards thrusting of crystalline complexes of Archaean to Palaeoproterozoic age, metasediments of the Krum- medal and Smallefjord sequences of Mesoproterozoic to early Neoproterozoic age, metasediments of the Eleonore Fig. 1 Geological map of North-East Greenland based on Stemmerik et al. (1997), Henriksen et al. (2008) and Kalsbeek et al. (2008a). Detailed map of Wol- laston Forland based on the digital Greenland geological map at a scale of 1:500 000 and the printed map series at a scale of 1:100 000. The locations of the Rødryggen-1 and Brorson Halvø-1 boreholes and the samples for zircon U-Pb age dating are shown. Thrust Fault/shear zoneNeoproterozoic and Caledonian granites Neoproterozoic (mainly Eleonore Bay Supergroup) Meso–Neoproterozoic metamorphic rocks (including Krummedal and Smalle�ord sequences) Archaean–Palaeoproterozoic crystalline complex Tectonic windows with crystalline rocks Devonian Cambrian–Silurian Triassic Permian Carboniferous Jameson Land G re e nlan d ice sh e e t Kong Oscar Fjord 100 km 25°W70°N 74°N Liverpool Land Score s b y S und A–G Localities for zircon age data from literature (see Fig. 9) Wollaston Forland Clavering Ø Hold with Hope Traill Ø Geographical Society Ø 72°N Palaeogene volcanic rocks Cretaceous Jurassic Quaternary Palaeogene sills and dykes Borehole Provenance sample A B A B D E C F D C C B A Shannon Ø Hochstetter Forland Kuhn Ø Kejser Franz Joseph Fjord A A Payer Land G 10 km 20°W 20°W Rødryggen-1 Fladebugt Young Sund Wollaston Forland Daneborg Brorson Halvø-1 123 4 https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 3 of 22 GEUSBULLETIN.ORG Bay Supergroup of Neoproterozoic age and sediments of Neoproterozoic to Silurian age (Kalsbeek et al. 2000, 2008b; Watt et al. 2000; Thrane 2002; Higgins et al. 2004). Caledonian metamorphism, migmatization and gran- ite intrusion took place in Ordovician to Silurian times, and the crustal thickening resulted in continental sedi- mentation during the Devonian, followed by post-Cale- donian terrestrial and marine sedimentation in the Carboniferous to Palaeogene (Stemmerik et  al. 1992; Kalsbeek et al. 2001; Gilotti et al. 2008; Larsen et al. 2008). Late Triassic – Middle Jurassic thermal subsidence in the sedimentary basins was followed by Middle Jurassic rifting that was succeeded by transgression in the Late Jurassic and then renewed rifting, which culminated in the latest Jurassic – earliest Cretaceous (Surlyk 2003). The Wollaston Forland peninsula provides one of the most complete stratigraphic records of the Jurassic and Early Cretaceous in North-East Greenland (Fig. 1). The cored sec- tion covers the Kimmeridgian to lower Barremian interval, which is divided into four formations: (1) the Bernbjerg Formation, (2) the Lindemans Bugt Formation (Storsletten Member), (3) the Palnatokes Bjerg Formation (Albrechts Bugt and Rødryggen Members) and (4) the Stratumbjerg Formation (Fig. 2). The Bernbjerg Formation spans the late Oxfordian to the early Volgian and forms an up to 500–600 m thick black mudstone – shale succession that accumu- lated in a tectonically-affected shelf setting (e.g. Surlyk et al. 2021). Rifting intensified during the Volgian, fragmenting the basin into a series of narrow, 10–30 km wide, westward tilted, fjord-like half-grabens. Major conglomeratic subma- rine fan-delta systems (Lindemans Bugt Formation, Rigi Member) developed in the most proximal fault block reach- ing a maximum thickness of 2 km (Surlyk 1978; Henstra et al. 2016). The coeval palaeoenvironmental development in more distal fault blocks has remained poorly understood due to lack of outcrops but is well-recorded in the studied cores. The new data indicate deep basinal sedimentation (distal part of Lindemans Bugt Formation) and detachment of the Permpas–Hühnerbjerg Blocks (in which the studied boreholes are located) from the coastal deltaic systems (Hovikoski et al. 2023a (this volume), b). The rift climax lasted until the Valanginian and was fol- lowed by waning rift activity and transgression in the west- ern part of the study area (Surlyk 1978, 1984, 1990, 2003). An up to 600 m thick succession of gravity-flow deposits with conglomerates and sandstones (Palnatokes Bjerg For- mation, Young Sund Member) accumulated in the proximal fault block, whereas fossiliferous mudstones (Albrechts Bugt and Rødryggen Members) were deposited in basinal areas and on submarine block crests (Surlyk 1978, 1984, 2003; Surlyk & Korstgård 2013; Hovikoski et al. 2018). The Rødryggen-1 and Brorson Halvø-1 cores penetrate both mudstone members. New biostratigraphic data (Nøhr-Han- sen et  al. 2020; Alsen et  al. 2023, this volume) suggest a Valanginian to Hauterivian age for these deposits. Towards the east, fault activity continued until the Barremian and led to the deposition of the coarse-grained Falskebugt Member (Piasecki et al. 2020). During the late Hauterivian, deposits of the Palnatokes Bjerg Formation were drowned and succeeded by sub-storm wave-base bioturbated mud- stones of the Stratumbjerg Formation (Bjerager et al. 2020). A several metres thick upper Hauterivian to lower Barre- mian interval of the lowermost Stratumbjerg Formation is recorded at the top of the Brorson Halvø-1 core (Alsen et al. 2023, this volume) and younger parts of the formation of Barremian to Albian age are present in outcrops near the drill site (Piasecki et al. 2020). 3. Methodology 3.1 Petrography The petrographic and mineralogical characteris- tics of cemented and laminated mudstones in the Fig. 2 Stratigraphic scheme with vertical lines showing the Rødryggen-1 (RØ-1) and Brorson Halvø-1 (BH-1) cored successions. Al: Albrechts Bugt Mb. B: Bernbjerg Fm. Ba: Bastians Dal Fm. J: Jakobsstigen Fm. L: Laugeites Ravine Mb. Li: Lindemans Bugt Formation. Li (S): Lindemans Bugt Fm (Storsletten Mb). Mu: Muslingebjerg Fm. N: Niesen Mb. Pa: Pal- natokes Bjerg Fm (Young Sund Mb). Pay: Payer Dal Fm. Pe: Pelion Fm. R: Rødryggen Mb. Ri: Rigi Mb. Str: Stratumbjerg Fm. Ug: Ugpik Ravine Mb. Modified from Bojesen-Koefoed et al. 2023a, this volume). S N Alluvial/delta plain, paralic, sand-dominated Coal Shallow marine sandstones Shelf transition – sandstones, mudstones, heteroliths O�shore/basinal mudstones Deep marine sandstones Deep marine conglomerates Calcareous sandy marine mudstones Red marine mudstones Hiatus/condensed ChronostratigraphyWollaston Forland – Kuhn Ø R ? Al Str BH-1 RØ-1Pa No data Li Li (S)Ri N B J Pe Ug Pay Mu Ba Onlaps crystalline basementOnlaps Upper Permian W E Barremian Hauterivian Valanginian Ryazan- ian Volg- ian Berri- asian Tithon- ian Kimmeridgian Oxfordian Callovian Bathonian Bajocian Aalenian C re ta ce ou s Ju ra ss ic Lo w er U pp er M id dl e U M U L L U M L U M L U M L U L U M L L ? https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 4 of 22 GEUSBULLETIN.ORG Rødryggen-1 and Brorson Halvø-1 cores were stud- ied by transmitted and reflected light microscopy as well as by scanning electron microscopy (SEM). Sam- ples of fracture fillings and sandy intervals were also examined. Polished thin sections were prepared from selected intervals in the cores representing diage- netic features characteristic of the different types of lithologies. The thin sections were impregnated with blue epoxy to ease identification of open pore space. Half of each thin section was etched and stained with sodium cobaltinitrite to facilitate K-feldspar identification. The SEM analyses were performed at the Geological Survey of Denmark and Greenland (GEUS) using a Philips XL40 SEM equipped with a ThermoNoran Energy Dispersive X-ray spectrometry (EDS) detector that was used to analyse the chemis- try. Selected samples were studied with a backscat- tered electron (BSE) detector on carbon-coated thin sections and with a secondary electron (SE) detector on gold-coated rock chips. The mineralogy of each type of lithology present in the Rødryggen-1 and Brorson Halvø-1 cores was analysed by X-ray diffrac- tion (XRD) at the University of Copenhagen, Denmark, and GEUS. The edge of the core was removed to avoid contamination. The bulk mineralogy was measured on a Bruker Advance D8 diffractometer with a Lynx- Eye detector using samples crushed to <63 μm apply- ing the Bragg–Brentano method. Semi-quantification of the bulk mineralogy was obtained by the Rietveld method (Rietveld 1969; McCusker et  al. 1999). The clay fraction analysis was carried out on a Philips 1050 goniometer with fixed divergence, anti-scatter slits and Co-Kα radiation (pulse high selection and Fe-filter). Chemical pre-treatment with NaOCl at pH 9.0 was used to remove organic matter. The sam- ples were dispersed ultrasonically in distilled water to acquire the clay fraction (<2 µm). The >30 µm fraction was removed by density separation and the intermediate fraction by centrifugation in a centrifu- gal particle size analyser (Slater & Cohen 1962). The suspensions were flocculated in 1 M NaCl, and excess salt was removed by centrifugation and washing with water and ethanol. Three orientated specimens were made for each sample by the pipette method, com- prising Mg-saturated air-dry, Mg-saturated with glyc- erol, and K-saturated air-dry heated at 300°C for 1 h. An X-ray diffractogram was produced for each of the saturated specimens on which the discrete minerals were identified from peak positions (Hillier 2000) and semi-quantified by application of correction factors. 3.2 Zircon U-Pb geochronology The Rødryggen-1 and Brorson Halvø-1 cores did not contain sufficiently coarse material to apply detrital zircon U-Pb age dating methods. Instead, outcrop sam- ples collected from three locations east of the Rødryg- gen-1 drill site and a location situated north-east of the Brorson Halvø-1 drill site were used for the prov- enance analysis (Fig.  1). The samples collected near the Rødryggen-1 drill site consist of silty sandstone to sandy siltstone belonging to the Bernbjerg Forma- tion, corresponding to the lower part of the cored succession. The sandstone sampled near the Bror- son Halvø-1 drill site belongs to the Albian part of the Stratum bjerg Formation, so it is younger than the part of the formation encountered in the Brorson Halvø-1 core. The detrital zircon U-Pb age analyses were per- formed by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) at GEUS. Samples were crushed and sieved to retrieve the grain-size fraction <500  µm. A water-shaking Wilfley table was used to obtain heavy mineral concentrates. Zircon grains were hand-picked in a random way to ensure that a range of grain sizes, shapes and colours were included. The pol- ished epoxy mount with the zircon grains was cleaned in an ultrasonic bath with propanol and loaded into the sample cell of the laser ablation system for radio- metric age dating. The data were acquired with a sin- gle spot analysis on individual zircon grains. A  beam diameter of 30 µm and a crater depth of c. 15–20 µm were used. The  amount of ablated material was c. 200–300 ng for the ablation time of 30 sec. The ablated material was analysed on an Element2 (Thermo Fin- nigan) single-collector, double focusing, magnetic sector-field, inductively coupled plasma mass spec- trometer with a fast-field regulator for increased scan- ning speed. The total acquisition time was 60 sec for each analysis, of which the first 30 sec were used to measure the gas blank. The instrument was tuned to give large, stable signals for the 206Pb and 238U peaks, low background count rates (typically around 150 counts per second for 207Pb) and low oxide produc- tion rates (238U16O/238U generally below 2.5%). 202Hg, 204(Pb+Hg), 206Pb, 207Pb, 208Pb, 232Th and 238U intensities were determined through peak jumping using elec- trostatic scanning in low resolution mode and with the magnet resting at 202Hg. Mass 202Hg was measured to monitor the 204Hg interference on 204Pb where the 202Hg/204Hg ≡ 4.36, which can be used to correct signif- icant common Pb contributions using the model Pb composition of Stacey & Kramers (1975). Standard-sample bracketing using the GJ-1 zircon (Jackson et  al. 2004) was used to correct the elemen- tal fractionation induced by the laser ablation and the instrumental mass bias on measured isotopic ratios. Long-term external reproducibility was monitored by repeated analyses of the Plešovice zircon standard (Sláma et  al. 2008). The reported ages are based on https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 5 of 22 GEUSBULLETIN.ORG 207Pb/206Pb derived ages for the >0.8 Ga (billion years) analyses and 206Pb/238U ages for the <0.8 Ga analyses, since the latter is more precise for the younger age range, and a natural gap between age populations exists. The propagation of the analytical errors follows the prin- ciples of Sambridge & Lambert (1997). Age measure- ments were discarded if they lacked a stable 207Pb/206Pb plateau or for U/Pb or Pb/Pb error >10%. A correction for common Pb was applied on a small fraction (≤7%) of the concordant analyses from each sample. The data are plotted using kernel density estimation (Vermeesch 2012) employing analyses with <10% discordance. The analytical data are reported in Supplementary File S1. 4. Results 4.1 Lithology The studied succession was deposited during a pro- tracted rifting episode that is differentiated into four discrete rift phases: (1) early rifting during the Kimmerid- gian part of the Bernbjerg Formation, (2) rift acceleration during the Volgian part of the Bernbjerg Formation, (3) rift climax during deposition of the Lindemans Bugt For- mation and (4) waning rifting during deposition of the Pal- natokes Bjerg Formation (Figs 3 and 4; Surlyk 1978, 2003). These major rift phases resulted in significant shifts in depositional conditions that are reflected in the lithologi- cal characteristics observed in the different stratigraphic units in the Rødryggen-1 and Brorson Halvø-1 cores. In the cored sections, the Bernbjerg Formation com- prises dark grey mudstones with interlaminated coarse siltstones to very fine sandstones in some intervals (Fig. 5A). The Lindemans Bugt Formation consists of dark grey clayey mudstones (Fig. 5C) with a larger content of fossils and pyrite than in the Bernbjerg Formation. The Albrechts Bugt Member of the Palnatokes Bjerg Forma- tion comprises light grey mudstones (Fig. 5D) that differ from the Lindemans Bugt Formation in being more cal- careous, sandy and bioturbated. The Rødryggen Mem- ber of the Palnatokes Bjerg Formation consists of red hematitic mudstones with intercalated sandy mudstones (Fig.  5E). The Stratumbjerg Formation contains biotur- bated grey mudstones (Fig.  5F). The sedimentological characteristics are described in more detail by Hovikoski et al. (2023a, this volume). Carbonate-cemented intervals occur in all the strati- graphic units and are characterised by lower gamma-ray values (Figs 3, 4) and lighter colours (Fig. 5B). The lighter colours are also evident in the microscopic appear- ance of the cemented mudstones due to the lower clay mineral content as compared to the uncemented mudstones (Figs 6A, 6B). Pyrite is evident in many core intervals as well as various macrofossils, deformation structures, faults and fractures (Figs 3 and 4). 4.2 Detrital components The mineralogy of the Rødryggen-1 and Brorson Halvø-1 cores based on XRD analyses is presented in Figs 3 and 4 for the 27 analysed mudstones and two samples of cemented fractures. Quartz is the most abundant min- eral amounting to 12–48 wt% with an average of 29 wt%, which is present as silt- and sand-sized grains in the mud- stones (Fig. 6C). K-feldspar and plagioclase/albite occurs in amounts of up to 11 and 18 wt%, respectively, and each of them are present as 6 wt% on average. Petrographic analysis of the K-feldspar grains reveals that they are gen- erally well-preserved, whereas the plagioclase and albite grains are often partially dissolved (Fig.  6D). Apatite is found as detrital clasts (Fig. 6E) in amounts of 4 wt% on average with the highest contents up to 16 wt% occurring in a condensed interval in the lower part of Lindemans Bugt Formation in the Rødryggen-1 core. Calcite is present as detrital clasts, including bio- clasts in the Palnatokes Bjerg Formation, in both the Albrechts Bugt and Rødryggen Members. The Bern- bjerg and Lindemans Bugt Formations are rich in organic matter including some coal fragments. Detrital heavy minerals are found in accessory amounts and comprise primarily ilmenite, leucoxene, rutile, magne- tite, zircon and garnet in the form of almandine. Mus- covite could not be differentiated from illite by XRD but was observed in thin section. The mica minerals pri- marily consist of muscovite with subordinate biotite. The micas are generally aligned parallel to the lamina- tion and are often cleaved into thin sheets and bend around less ductile grains (Fig. 6C). Most of the clay minerals are detrital as testified by the absence of growth structures and by their tan- gential orientation around the other detrital miner- als (Fig.  6F). Kaolinite is present in the matrix of all the mudstones and occurs in higher amounts in the Rødryggen-1 core than in the Brorson Halvø-1 core (Figs 3, 4). Kaolinite is found in amounts up to 17 wt% with an average of 10 wt%. Mixed-layer illite-smectite is found in amounts of 7 wt% on average with the highest contents occurring in the Brorson Halvø-1 core and especially in the sample from the Stratum- bjerg Formation where it constitutes 28 wt%. Illite occurs with an average of 13 wt% and is more abun- dant overall in the Brorson Halvø-1 core than in the Rødryggen-1 core. The smallest illite contents within each well occur in the Palnatokes Bjerg Formation and the highest contents of up to 25 wt% are present in the Bernbjerg Formation. Some of the illite is authigenic as evident by its morphology, but the proportion of detrital to authigenic illite cannot be quantified. Chlorite is found in all samples from the Brorson Halvø-1 core (Fig. 6F), except the two deepest samples from the Bernbjerg Formation, and its content increases https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 6 of 22 GEUSBULLETIN.ORG Fig. 3 Mineralogy from XRD of the Rødryggen-1 core plotted with the sedimentological log. Chronostratigraphy from Alsen et al. (2023, this volume). See Fig. 4 for legend. Chronostrat.: chronostratigraphy. Lithostrat.: lithstratigraphy. GR: gamma ray. API: American Petroleum Units. B er nb je rg F m Li nd em an s Bu gt F m W ol la st on F or la nd G ro up H al l B re dn in g G ro up Pa ln at ok es B je rg F m A lb re ch ts B ug t M b clay silt VF F M C VC sand GR (API) Rødryggen-1Chrono- strat. Litho- strat. Tectonic phase Ki m m er id gi an Lo w er V ol gi an M id dl e V ol gi an U pp er Ry az an ia n Lo w er R ya za ni an U pp er V ol gi an U pp er Va la ng ia n Lo w er V al an gi an Py Py Py Py An An An An An An Py Py Py Py Py Py Py Structures and fossils2200 PyRi ft c lim ax W an in g ri ft Ri ft a cc el er at io n Ea rl y ri ft 110 120 130 140 150 160 170 180 190 200 210 220 0 10 20 30 40 50 60 70 80 90 100 230 234.5 m Mineralogy (wt%) 0 20 40 60 80 100 2.70 3.30 13.31 22.27 23.88 26.60 57.43 66.45 74.60 76.67 89.62 89.66 154.54 173.51 173.63 194.29 194.41 205.73 221.00 222.67 227.32 Fracture �ll m Quartz K-feldspar Plagioclase Apatite Calcite Ankerite-Dolomite Pyrite Kaolinite Mixed-layer clays Illite Chlorite Vermiculite https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 7 of 22 GEUSBULLETIN.ORG Fig. 4 Mineralogy from XRD of the Brorson Halvø-1 core shown alongside the sedimentological log. Chronostratigraphy from Alsen et al. (2023, this volume). Chronostrat.: chronostratigraphy. Lithostrat.: lithstratigraphy. GR: gamma ray. API: American Petroleum Units. Py Py Py Py Py Py Py Py Py Py Py Py Py Py Py MFR MFR ? ? ? Py Py Py Py Py Py Py Py Py Py Py Py Py Py Py Py An An An An Py Py Py dominated Py Py Py Py Py Py Py Py Py Py Brorson Halvø-1 225.7 110 120 130 140 150 160 170 180 190 200 210 220 0 10 20 30 40 50 60 70 80 90 100 An l. Ba rr - em ia n Lo w er V ol gi an Ki m m er id gi an clay silt VF F M C VC sand u. H. up pe r V al an gi ni an – m id de l H au te ri vi an u. R. m.Vol. ? u. V. mChrono- strat. Litho- strat. Tectonic phase Structures and fossils2200 B er nb je rg F m H al l B re dn in g G ro up Li nd e- m an s B ug t F mW ol la st on F or la nd G ro up Pa ln at ok es B je rg F m A lb re ch ts B ug t M b R ød ry gg en M b St ra tu m - bj er g Fm B ro rs on H al vø G r. Ri ft cl im ax W an in g ri ft Ri ft a cc el er at io n Ea rl y ri ft m Mineralogy (wt%) 0 20 40 60 80 100 3.18 9.70 23.20 35.20 38.15 52.71 117.70 212.70 MFR Concretion Open fractures Clay clast Bivalve Wave ripple cross-strati�cation Coal Belemnite Contorted lamination Shell fragments Plant fragments Ripple cross-strati�cation Faults Fractures Very �ne sandstone/coarse siltstone Interlaminated sandstone and mudstone Calcite-cemented sandy mudstone Ankerite and dolomite-cemented mudstone Planar laminated mudstone Mottled lamination Pyrite Ankerite Ammonite Onychites Slump Loading Synaeresis crack Scour-and-�ll (gutter cast?) Mud �occule ripple Py An Fracture �ll Quartz K-feldspar Plagioclase Apatite Calcite Ankerite-Dolomite Hematite Pyrite Kaolinite Mixed-layer clays Illite Chlorite Vermiculite GR (API) https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 8 of 22 GEUSBULLETIN.ORG upwards with the highest amount of 18 wt% occurring in the Stratumbjerg Formation (Figs 3, 4). In the Rødryg- gen-1 core, chlorite is only present in the Palnatokes Bjerg Formation where it occurs in amounts of 2–4 wt%. Vermiculite is not present in the mudstones from the Brorson Halvø-1 core except for a small content (1 wt%) in the Stratumbjerg Formation. In the Rødryggen-1 core, vermiculite is present in all samples from the Lindemans Bugt and Palnatokes Bjerg Formations in contents of 4–14 wt%, whereas it is absent in the Bernbjerg Formation. 4.3 Authigenic minerals Pyrite is on average 5 wt% and it was the first mineral that precipitated in the sediments. Pyrite is present Fig. 5 Core photos of the mudstone texture of cemented versus uncemented mudstones. BH-1: Brorson Halvø-1 core. RØ-1: Rødryggen-1 core. A: Laminated sandy mudstone. B: Cemented mudstone. C: Laminated pyritic mudstone. D: Bioturbated mudstone. E: Bioclastic hematitic cemented mudstone. F: Bioturbated mudstone. A Bernbjerg Fm, RØ-1, ~166 m 1 cm B Lindemans Bugt Fm, Storsletten Mb, RØ-1, ~76.6 m 1 cm F Stratumbjerg Fm, BH-1, ~2 m 1 cm C Lindemans Bugt Fm, Storsletten Mb, RØ-1, ~64 m 1 cm E Palnatokes Bjerg Fm, Rødryggen Mb, BH-1, ~20 m 1 cm D Palnatokes Bjerg Fm, Albrechts Bugt Mb, RØ-1, ~2.7 m 1 cm https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 9 of 22 GEUSBULLETIN.ORG in all formations except some parts of the Stratum- bjerg and Palnatokes Bjerg Formations in the Brorson Halvø-1 core (Figs 3, 4). It is often found in association with organic matter (Fig.  7A). The highest amounts (4–14 wt%) are found in the Lindemans Bugt Formation where the pyrite framboids are often overgrown by euhedral pyrite (Fig. 7B). Only framboidal pyrite is pres- ent in the remaining formations where it constitutes 4–7 wt% in the Bernbjerg Formation and 0–3 wt% in the Pal- natokes Bjerg Formation. Although the kaolinite crystals have euhedral shapes, they are likely to have been transported before Fig. 6 Texture and detrital phases. A: Typical mudstone texture. B: Cemented mudstone texture. C: Quartz occurs as silt- and sand-sized grains in the mudstones. D: Partially dissolved albite grain. E: Apatite occurs as detrital clasts. F: Most clay minerals are detrital such as chlorite. A Bernbjerg Fm, TL image, RØ-1, 201.81 m B Bernbjerg Fm, TL image, RØ-1, 187.50 m C Bernbjerg Fm, BSE image, BH-1, 212.70 m D Palnatokes Bjerg Fm, BSE image, RØ-1, 13.31 m E Lindemans Bugt Fm, BSE image, RØ-1, 89.96 m F Stratumbjerg Fm, SE image, BH-1, 3.18 m 100 μm 100 μm 20 μm50 μm 10 μm 5 μm M Q Q C F A K D A Ap Ch K BH-1: Brorson Halvø-1 core RØ-1: Rødryggen-1 core TL: transmitted light CN: crossed nicols BSE: backscattered electron SE: secondary electron A: ankerite Ap: apatite B: barite C: calcite Ch: chlorite D: dolomite F: feldspar K: kaolinite M: mica Ml: mixed-layer clay O: opal Om: organic matter Pe: pyrite euhedra Pf: pyrite framboid Q: quartz https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 10 of 22 GEUSBULLETIN.ORG deposition since they do not occur in well-defined booklets (Fig. 7C). However, some detrital grains have been kaolinised, including some of the muscovite and feldspar grains, which must have happened within the sediment since they would have disintegrated during transport. It is often difficult to distinguish unambigu- ously between the detrital and authigenic clay minerals, but the morphology of the mixed-layer illite-smectite and illite indicate that part of it is authigenic. Fibrous and hairy illite was observed using SEM. Thin quartz overgrowths have mainly precipitated in the coars- er-grained intervals (Fig. 7C) and overgrow pyrite and kaolinite. Barite has precipitated in some of the mud- stones where it formed as the last authigenic phase. A Bernbjerg Fm, BSE image, BH-1, 52.71 m B Lindemans Bugt Fm, BSE image, RØ-1, 76.47 m C Bernbjerg Fm, SE image, RØ-1, 227.32 m D Lindemans Bugt Fm, SE image, RØ-1, 90.01 m E Bernbjerg Fm, BSE image, RØ-1, 187.50 m F Palnatokes Bjerg Fm, BSE image, RØ-1, 23.88 m 20 μm 20 μm 5 μm 5 μm5 μm 30 μm Om Pf Pf Pe A D Q K A B Mi Pf A D Q C Fig. 7 Authigenic minerals. A: Framboidal pyrite has often formed in connection with organic matter. B: Euhedral pyrite has only formed in Lindemans Bugt Formation where it has overgrown pyrite framboids. C: Quartz has overgrown detrital kaolinite. D: Barite has overgrown ankerite rhombs. E: Dolomite is the dominant carbonate cement in Bernbjerg and Lindemans Bugt Formations. F: Calcite is the dominant carbonate cement in Palnatokes Bjerg Formation. See Fig. 6 for abbreviations. https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 11 of 22 GEUSBULLETIN.ORG It occurs as string-like precipitations and as euhedral crystals overgrowing ankerite (Fig. 7D). Barite was iden- tified by EDS but has formed in such small amounts that it could not be estimated by XRD analysis. Pervasive carbonate cementation of the mudstones is found in some intervals of all the studied forma- tions, and these intervals are characterised by low gamma-ray values in the natural gamma log (Figs 3, 4). High concentrations of bioclasts or micrite are present in the carbonate-cemented intervals, except for those with siderite. Dolomite is the dominant carbonate min- eral in the Bernbjerg and Lindemans Bugt Formations, whereas calcite is dominant in the Palnatokes Bjerg Formation and siderite is dominant in the Stratum- bjerg Formation. Dolomite and ankerite could not be clearly discrimi- nated by XRD so they have been grouped as ankerite– dolomite in the XRD results (Figs 3, 4). However, both minerals are present since they were identified by EDS. They are found in all formations with the highest abun- dance in the Bernbjerg Formation (maximum 34 wt%) followed by Lindemans Bugt Formation (maximum 8 wt%). Poikilotopic dolomite occurs in highest abundance, whereas ankerite occurs mostly as smaller rhombs (Fig.  7E). Ankerite is often precipitated between exfoli- ated mica flakes. An outwards increase in Fe content is observed in both the dolomite and ankerite crystals. Calcite occurs in amounts of 2–4 wt% in the samples from the Bernbjerg and Lindemans Bugt Formations, reaching 6–54 wt% in the Palnatokes Bjerg Formation comprising both detrital and authigenic calcite that is poikilotopic and micritic (Fig.  7F). A calcite content of 1 wt% is found in the sample from the Stratumbj erg Formation. This sample does not contain siderite, but it is present in other samples from this stratigraphic unit where it has precipitated as an early phase. 4.4 Bioclasts The Bernbjerg and Lindemans Bugt Formations contain numerous calpionellids that are most abundant in the cemented mudstones. The calpionellids and other shell material in the Bernbjerg and Lindemans Bugt Forma- tions are recrystallised, but moulds of molluscs and ammonites have been found (Alsen et al. 2023). Calpi- onellids are calcareous microfossils of uncertain affin- ity. They have oblong shells which have been filled with either dolomite or micritic calcite and often also anker- ite and pyrite (Fig. 8A). Pyrite precipitated mostly along shell rims though sometimes filling most of the internal cavity. Ankerite formed small euhedral crystals, most of which precipitated on the exterior of the bioclasts. Poi- kilotopic dolomite crystals precipitated in most of the remaining cavity, but some porosity is often preserved (Fig. 8B). Fossils in the Palnatokes Bjerg Formation include ostracods, brachiopods, foraminifera and inoceramid bivalves (Alsen et  al. 2023). The formation contains abundant calcispheres, especially in the cemented inter- vals. They have not been recrystallised as seen by the characteristic test (Fig. 8C) and by the extinction pattern following the growth structure in other fossils. These calcispheres are probably calcareous dinoflagellate cysts and have a spherical test. Calcite has precipitated in the interior, and small ankerite crystals have some- times formed within the calcite (Fig. 8D). 4.5 Fractures Small fractures are present in most of the core and are most evident in the cemented intervals where they cut through the carbonate-cemented fabrics. Opal has often formed along the rims of the frac- tures where it radiates in multiple layers and forming spherical layers around a protruding matrix (Fig. 8E). The remaining parts of the fractures are filled with dolomite in which the Fe content decreases towards the middle of the fractures (Fig. 8F). The dolomite has occasionally replaced some of the opal along its outer rim (Fig. 8E). XRD analyses have been made of fracture fills comprising one sample selected from each well in the Bernbjerg Formation where fractures are most abundant, and show that dolomite is the dominant fracture-filling cement (Figs 3, 4). Fracturing has hap- pened several times as seen by the cross-cutting relationships of the fracture generations, where each of them became cemented prior to the next gen- eration of successively wider fractures. The largest encountered fractures are up to a few centimetres wide. The last generation of fractures were not filled by any minerals and thus increased the porosity and permeability. 4.6 Zircon U-Pb ages The detrital zircon U-Pb ages of the four outcrop samples from Wollaston Forland (Fig. 1) cover a broad Mesoar- chaean to Palaeozoic age span (Fig. 9). The discordant ages (comprising 21–28%) are not plotted but included in Supplementary File S1. The three samples from the Bernbjerg Formation (samples 1–3, Fig. 9) all contain a pronounced Archaean zircon age population with peak ages at 2.75–2.65 Ga (comprising 7–10% in each sam- ple), whereas only a single Archaean zircon grain was found in the sample from the Stratumbjerg Formation (sample 4, Fig. 9). The dominant age populations of the samples are present within the 2.0–1.6 Ga interval (comprising 42–75% in each sample), although the relative pro- portions between the age populations vary. In the https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 12 of 22 GEUSBULLETIN.ORG Bernbjerg Formation, an age population with peak age at 1.97 Ga is dominant in two of the samples (samples 1 and 3, comprising 23–24%) and evident in the third (sample 2, comprising 10%), but not in the sample from the Stratumbjerg Formation. The dominant age popu- lation in the Stratumbjerg Formation sample has peak age at 1.88 Ga (sample 4, comprising 39%), and this population is less pronounced and slightly older in the Bernbjerg Formation samples. An age population with peak ages at 1.65–1.63 Ga is pronounced in the sam- ple from Stratumbjerg Formation (sample 4, compris- ing 17%) and in two of the samples from the Bernbjerg Fig. 8 Bioclasts and fracture fillings. A–B: Recrystallised calpionellids filled with combinations of calcite, dolomite, ankerite and pyrite, and occasionally with internal porosity. Calpionellids are present in Bernbjerg and Lindemans Bugt Formations. C–D: Well-preserved calcispheres filled with calcite and small ankerite rhombs. Calcispheres are present in Palnatokes Bjerg Formation. E: Opal precipitated in several zones in a fracture and succeeded by dolomite, which has replaced some opal along the contact (arrow). F: Opal along fracture rims and succeeded by dolomite with lower Fe content in the middle. Fractures are most abundant in Bernbjerg Formation. See Fig. 6 for abbreviations. A Lindemans Bugt Fm, TL image, RØ-1, 76.47 m B Lindemans Bugt Fm, BSE image, RØ-1, 76.47 m C Palnatokes Bjerg Fm, SE image, RØ-1, 13.31 m D Palnatokes Bjerg Fm, BSE image, RØ-1, 13.31 m E Bernbjerg Fm, CN image, RØ-1, 187.50 m F Bernbjerg Fm, BSE image, RØ-1, 187.50 m 100 μm 20 μm 10 μm5 μm 300 μm 500 μm D C Pf DPf C A C O D D D O O https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 13 of 22 GEUSBULLETIN.ORG Formation (samples 2 and 3, both comprising 16%). A population with peak age of 1.74 Ga is slightly less prominent in the same three samples (comprising 9–14% in each sample), whereas both age populations are less prominent in the last sample from the Bern- bjerg Formation (sample 1; Fig. 9). A wide range of Mesoproterozoic zircon ages are found in all four samples (comprising 11–38% in each Fig. 9 Zircon U-Pb age distributions of the Upper Jurassic – Lower Cretaceous sediments (1–4) compared to selected zircon ages from the region (A–G: Strachan et al. 1995; Watt et al. 2000; Thrane 2002; Elvevold et al. 2003; Kalsbeek et al. 1993; Leslie & Nutman 2003; Sláma et al. 2011; Olivarius et al. 2018b; Barham et al. 2020; Olierook et al. 2020). The Phanerozoic zircon ages in A–C are from the intruded Caledonian granites. The sampling locations are shown in Fig. 1. The ages are plotted using kernel density estimation (Vermeesch 2012) and histograms with a bin interval of 25 million years. Zircon ages with <10% discordancy are plotted. “n/N” denotes the number of concordant analyses out of the total number of analyses. See Fig. 1 for locations. 0 30 15 0 5 10 Pr ob ab ili ty Pr ob ab ili ty Pr ob ab ili ty Pr ob ab ili ty Pr ob ab ili ty N um be r o f g ra in s 0 3 6 0 8 4 0 8 4 0 30 15 0 20 10 Pr ob ab ili ty Pr ob ab ili ty Pr ob ab ili ty 0 6 3 0 6 3 0 8 4 Pr ob ab ili ty Pr ob ab ili ty 4 3 2 1 F E D C B A Pr ob ab ili ty G 0 40 20 Age (Ga)0.0 1.0 2.0 3.0 4.00.5 1.5 2.5 3.5 Neoproterozoic Mesoproterozoic Palaeoproterozoic ArchaeanPhanerozoic Neoproterozoic metasediments Eleonore Bay Supergroup Nathorst Land Group Middle–Upper Devonian sediments Kap Koltho� and Kap Graah Groups Upper Jurassic sediments Hall Bredning Group Hareelv Formation Lower Cretaceous sediments Hold with Hope Group Steensby Bjerg Formation Upper Jurassic sediments Hall Bredning Group Bernbjerg Formation Upper Jurassic sediments Hall Bredning Group Bernbjerg Formation Upper Jurassic sediments Hall Bredning Group Bernbjerg Formation Lower Cretaceous sediments Brorson Halvø Group Stratumbjerg Formation n/N = 83/115 This study n/N = 112/150 This study n/N = 103/135 This study n/N = 81/103 This study 2 samples, n/N = 120/120 Sláma et al. 2011 6 samples, n/N = 660/945 Olivarius et al. 2018b 5 samples, n/N = 524/524 Sláma et al. 2011 6 samples, n/N = 490/960 Olierook et al. 2020 Archaean–Palaeoproterozoic rocks Crystalline basement complexes Meso–Neoproterozoic metasediments Krummedal and Smalle�ord sequences 6 samples, n/N = 114/181 Strachan et al. 1995, Watt et al. 2000, Leslie & Nutman 2003 15 samples, n/N = 127/147 Kalsbeek et al. 1993, Thrane 2002, Elvevold et al. 2003 Lower Cretaceous sediments Wollaston Forland Group Lindemans Bugt & Palnatokes Bjerg Formations 7 samples, n/N = 459/935 Barham et al. 2020 2.67 1.96 1.85 1.65 1.66 0.43 0.42 0.38 2.47 2.71 1.96 1.10 1.36 1.49 1.64 1.50 1.090.94 0.42 0.42 2.74 1.711.64 1.48 1.321.12 2.662.51 1.96 1.89 1.65 1.731.11 1.03 0.43 1.461.38 1.14 1.74 2.81 1.88 1.01 1.51 2.50 2.79 1.97 1.971.89 1.63 1.41 2.65 2.74 1.74 1.72 1.65 1.56 1.28 0.41 1.97 2.72 1.90 1.90 1.74 1.64 0.45 1.64 0.41 1.88 1.74 0.40 1.73 1.91 1.10 2.52 1.731.64 2.940.41 https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 14 of 22 GEUSBULLETIN.ORG sample) with less pronounced age populations as com- pared to the Palaeoproterozoic populations. Few Neo- proterozoic zircons are encountered (comprising 1–6% in each sample), and an age gap occurs at 0.9–0.5 Ga except for a few grains (Fig.  9). Small Palaeozoic age populations of 2–4 grains are found in all samples with peak ages varying between 0.45 and 0.38 Ga (compris- ing 2–5% in each sample). The oldest and youngest of these Ordovician–Devonian zircons, with ages of 474 ± 14 Ma and 364 ± 3 Ma, respectively, are both from the Bernbjerg Formation. 5. Discussion 5.1 Provenance analysis The Mesoarchaean to Palaeozoic zircon age popula- tions found in the four analysed samples of Upper Jurassic – Lower Cretaceous sediments from Wol- laston Forland are comparable (Fig. 9). The age distri- butions of the studied sediments are all characterised by a dominance of 2.0–1.6 Ga ages and by containing the full range of zircon ages within this time interval, although the relative proportion between the proba- bilities of the age populations varies. Therefore, the sediments presumably have the same overall prove- nance in which the proportion between the Palaeo- proterozoic zircon ages varies. However, some of the differences in age distributions between the samples may possibly be the result of bias related to min- eral separation with handpicking of grains for anal- ysis (e.g. Sláma & Košler 2012; Dröllner et  al. 2021). Selected zircon age data from the literature are plot- ted in Fig. 9 to facilitate comparison with possible sed- iment source rocks. As in the studied sediments, zircon age populations with a dominance of 2.0–1.6 Ga ages occur in Lower Cretaceous and Lower Triassic sediments from north- ern Hold with Hope, c. 80 km south-south-west of the study area (Fig.  1; Fonneland et  al. 2004; Sláma et  al. 2011). These sediments also contain Archaean, Meso- proterozoic and Palaeozoic age populations with low probabilities, although the Palaeozoic peak age is more pronounced than in the studied sediments (Fig.  9). The age populations of Upper Jurassic sediments from southern Jameson Land c. 450 km south-south-west of the study area are similar overall to the studied sedi- ments, but with significantly larger relative proportions of the Archaean and Mesoproterozoic age populations (Olivarius et al. 2018b). Lower Jurassic sediments from southern Jameson Land have a significantly different age distribution; they exhibit a limited number of peak ages reflecting their local provenance from the Liverpool Land High that was elevated at the time (Sláma et  al. 2011). The zircon age populations of Carboniferous and Devonian sediments along Kong Oscar Fjord and inner Kejser Franz Joseph Fjord (Moskusokse Fjord) are comparable to those in the studied sediments, except that the Mesoproterozoic and Palaeozoic pop- ulations are more prominent in these older sediments; furthermore, Archaean ages are more common in the Carboniferous sediments (Sláma et al. 2011). The Neo- proterozoic Lyell Land Group and Nathorst Land Group of the Eleonore Bay Supergroup have age distributions that are distinctly different from each other (Watt et al. 2000; Dhuime et al. 2007; Sláma et al. 2011; Olierook et al. 2020). Late Mesoproterozoic zircons are dominant in the Lyell Land Group along inner Kong Oscar Fjord (Segelsellskapet Fjord) with subordinate early Meso- proterozoic zircons, so these sediments show poor resemblance to the studied Upper Jurassic – Lower Cretaceous sediments. The Nathorst Land Group is dominated by late Palaeoproterozoic age populations and additionally contains several Mesoproterozoic age populations in addition to a smaller Archaean popu- lation; a sample of the intruded granites is included in Fig.  9 to show their Palaeozoic age (Olierook et  al. 2020). The metasediments of the Nathorst Land Group on Wollaston Forland are thus comparable to the stud- ied sediments, except that the metasediments contain a higher proportion of Mesoproterozoic zircons and no significant age populations in the 2.0–1.8 Ga interval. The Meso–Neoproterozoic metasediments of the Krummedal supracrustal sequence and Smallefjord sequence have dominant zircon age populations of late Palaeoproterozoic age and additionally contain Mesoproterozoic, early Neoproterozoic and Palaeozoic populations (Strachan et al. 1995; Watt et al. 2000; Les- lie & Nutman 2003). Thus, they are lacking 2.0–1.8 Ga age populations but otherwise resemble the age distri- butions of the studied sediments rather well. Archaean and Palaeoproterozoic crystalline basement complexes of the East Greenland Caledonides have age populations of 2.9–2.5 and 2.0–1.7 Ga (Kalsbeek et al. 1993; Thrane 2002; Elvevold et al. 2003). These are comparable to the oldest age populations found in the studied sediments, although the proportion of Palaeoproterozoic ages rela- tive to Archaean ages is higher in the sediments than in the basement complexes. Comparison between the samples analysed in this study and other sediments and possible sediment sources is made by multivariate statistical analysis by multidimensional scaling (MDS) visualised in an MDS diagram (Fig.  10). Here, similarities between samples are highlighted by solid lines revealing their proximity in Kolmogorov-Smirnov space, whereas dashed lines show smaller similarities. The sediments from this study have largest similarities to other Upper Jurassic and https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 15 of 22 GEUSBULLETIN.ORG Lower Cretaceous sediments, though some of these are as far away as Jameson Land. The largest differences are found between the end members comprising the Archaean–Palaeoproterozoic rocks and the Meso–Neo- proterozoic metasediments, indicating that a mixture of these is necessary to explain the range of ages encoun- tered in the sediments. 5.2 Sediment transport An overall north–south change in provenance in the upper Palaeozoic to Mesozoic succession in East Green- land is evident in the concentration of Palaeoproterozoic zircons in sediments on Wollaston Forland and Hold with Hope compared with sediments farther south, which contain a higher proportion of Mesoproterozoic zircons (Fig.  9). In particular, 2.0–1.8 Ga zircons are abundant in the central and northern parts of East Greenland in Triassic, Jurassic and Cretaceous sediments (Fonneland et al. 2004; Sláma et al. 2011; this study). This implies that there must be pronounced differences between either age or extent, or both, of the various sediment source rocks in the northern versus southern parts of the Cale- donides. Factors such as zircon fertility, sediment rout- ing, recycling and methodological bias may also affect the provenance signal (e.g. Dröllner et al. 2021). The primary source of the Upper Jurassic – Lower Cretaceous sediments on Wollaston Forland comprised the crystalline rocks of the East Greenland Caledonides or their derived sediments, or both. The Archaean and Palaeoproterozoic ages of the basement in Payer Land (Elvevold et al. 2003) match the oldest age populations of the studied sediments, so they may have been supplied from the crystalline complexes present west of Wol- laston Forland (Fig.  1). An additional sediment source is necessary to account for the late Palaeoproterozoic peak age of 1.65–1.63 Ga and the range of Mesopro- terozoic ages present in the studied sediments (Fig. 9), so this input must originate from erosion of Meso-Neo- proterozoic metasediments or Palaeozoic sediments, or both. The peak zircon age of 1.66–1.63 Ga is evident and often dominant in the sediments and metasediments of the East Greenland Caledonides (Fig.  9), except for the Lyell Land Group in which the peak ages are restricted to 1.5 and 1.1 Ga (Sláma et al. 2011). Peak ages of 1.5 and 1.1 Ga are also present in the Krum- medal supracrustal sequence, the Nathorst Land Group and younger sediments such as the Devonian and Carboniferous, but are not pronounced in the studied sediments. However, these peak ages are distinct in the Upper Jurassic sediments on Jameson Land that are age-equivalent to the Bernbjerg For- mation (Fig.  9). This is due to the lower proportion of Mesoproterozoic zircon ages in the northern part of the East Greenland Caledonides and in the stud- ied sediments, which makes the individual age pop- ulations in this interval less distinct. Some change in the drainage pattern must have occurred between the Kimmeridgian – early Volgian and the Albian, since the distinct  Archaean and 1.97 Ga populations in the Bern bjerg Formation are not evident in the Stratum- bjerg Formation where a 1.88 Ga population is dom- inant, as observed in Aptian sediments on northern Hold with Hope. Ages corresponding to these popu- lations are present in different crystalline basement complexes (Fig. 9). Zircon age distributions of the Bernbjerg, Lindemans Bugt, Palnatokes Bjerg and Stratumbjerg Formations from western Wollaston Forland are comparable to each other (Barham et al. 2020) and broadly comparable to the new results from northern Wollaston Forland (Fig. 9). However, the pronounced peak age of 1.97 Ga in the three samples from the Bernbjerg Formation in northern Wollaston For- land is not present in samples from the west. Likewise, Caledonian zircons are also virtually absent in the west in contrast to the northern part of Wollaston Forland. Thus, although much of the sediment on northern Wollaston Forland has been produced from reworking of sediment from western Wollaston Forland (Fig. 11), there must also have been an additional source that supplied sediment to the half-graben in which the Rødryggen-1 and Brorson Halvø-1 boreholes are situated. This additional sediment was probably supplied by axial transport from the north in accordance with the general depositional pattern in the Late Jurassic (Surlyk 2003). This is compatible with the abundance of Palaeoproterozoic basement to the north Fig. 10 Multidimensional scaling (MDS) diagram of zircon U-Pb age data. Plotted using Kolmogorov-Smirnov (K-S) dissimilarity (Vermeesch et al. 2016). The nearest neighbours in K-S space are shown by solid lines and the second nearest by dashed lines. See Fig. 10 for sample information. −0.6 −0.4 −0.2 0.0 0.2 0.4 0.6 –0 .6 –0 .4 –0 .2 0. 0 0. 2 0. 4 0. 6 Dim 1 D im 2 A B C D E F G 1 2 3 4 https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 16 of 22 GEUSBULLETIN.ORG and the presence of Caledonian granites in this area, though it is unknown if these granites were exposed in the Mesozoic. Changes in sediment composition are also evident in the clay mineral composition where chlorite and vermiculite were added upwards in the succession (Figs 3, 4). Another difference between the Bernbjerg For- mation and the younger deposits is evident in the zir- con age distributions from northern Wollaston Forland where the Stratumbjerg Formation lacks the Archaean and 1.97 Ga age populations that are present in the Bernbjerg Formation (Fig.  9). Thus, the rifting activity probably changed the erosional pattern resulting in altered sediment transport pathways. The kaolinite that is overgrown by authigenic quartz in the mudstones must comprise detrital kaolinite since they do not occur in well-defined booklets (Fig. 7C). The climate was humid subtropical at the time of deposition (Surlyk 2003), so kaolinite is the most likely clay mineral to have formed in the hinterland (Rateev et al. 2008), which explains its abundance in the mudstones. The presence of detrital kaolinite with preserved euhedral shapes points to a short transport distance from source area to place of deposition. This agrees with the interpreted proximity to the deltaic coast of North-East Greenland (Hovikoski et al. 2023b) with high mountains consisting of readily erodible material in the immediate hinterland (Henrik- sen & Higgins 2008). 5.3 Tectonic regime Comparing the mineralogy of the carbonate-cemented mudstones with uncemented mudstones shows that the mudstones had similar initial mineralogical compo- sitions, with the exception of the carbonate bioclasts, which represent the only additional component occur- ring in the cemented intervals (Figs 3, 4). Thus, in general, sediments with similar composition were supplied to the basin during deposition of the studied stratigraphic units, although the proportion between grains and clay min- erals varies in relation to the grain size (Figs 3, 4). Other differences in the detrital mineralogy include the varying content of apatite clasts and the addition of vermiculite and chlorite to the clay mineral assemblages upwards in the succession. The variations in detrital mineralogy and grain size of the studied sediments are the results of (1) changing tectonic regime of the depositional setting that changed the sediment transport pathways and sea-bot- tom topography, and (2) rotational block faulting that caused increasing basin depth and sediment starvation up through the succession (Hovikoski et  al. 2023a, this volume). Rifting also influenced the amount of deoxygen- ation and thereby the diagenetic evolution of the sedi- ments as reflected in the varying amount of precipitated pyrite. The calcareous bioclast abundance is largest in transgressive intervals and in some condensed intervals as is also the case for apatite clasts. The marine shelf setting of the Bernbjerg Formation with sediment supply from the deltaic coastline to the west (Fig. 11A) is reflected in the sandy component of the Fig. 11 Inferred structural setting of northern Wollaston Forland in Late Jurassic to Early Cretaceous time when submarine deposition of mud- stones took place during (A) early rifting, (B) rifting climax and (C) waning rifting in west (not waning in east, i.e. Falskebugt Member). Locations of the Rødryggen-1 (RØ-1) and Brorson Halvø-1 (BH-1) boreholes are shown as well as sediment transport directions. A) Early rift: Bernbjerg Formation B) Rift climax: Lindemans Bugt Formation C) Waning rift: Palnatokes Bjerg Formation & Stratumbjerg Formation BH-1RØ-1 N BH-1RØ-1 N BH-1RØ-1 N Axial sediment transport Basinwards sediment transport https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 17 of 22 GEUSBULLETIN.ORG mudstones with storm-wave influence in the lower part of the cored succession and in the presence of abundant silt and fine sand-sized quartz grains (Fig. 6C). Faulting intensified (Surlyk 2003), linked to the onset of coarse marine sedimentation proximally (Lindemans Bugt For- mation). At the culmination of rotational block faulting, a fault was created west of the study area resulting in westwards tilting of the resulting basin (Fig.  11B; Hov- ikoski et al. 2023b). The submarine fault scarp west of this half-graben blocked sediment input from the main- land, but some sediment was supplied into the basin by gravity flows originating at the fault scarp. The fairly short distance to the fault scarp resulted in the input of some silt-sized detrital grains despite the relatively sed- iment-starved environment. Clasts of quartz, feldspar, mica and apatite (Fig. 6E) were supplied by mass flows in addition to the detrital clay minerals. Vermiculite is absent in the Bernbjerg Formation in the Rødryggen-1 core but is found in all samples of the Lindemans Bugt and Palnatokes Bjerg Formations (Fig. 3). The cause of this change is not clear, but it may reflect the changed setting caused by block faulting whereby sediment supplied to the Rødryggen-1 drill site was sourced by the submarine fault scarp to the west during rift climax, and this input mixed with sediment supplied by axial transport during the waning rift phase (Fig. 11C). The high gamma-ray values of the Lindemans Bugt Formation in the Rødryggen-1 borehole (Fig. 3) are compatible with the fine-grained nature of the deposits in the centre of the half-graben where fine-crystalline vermiculite is dominant and coarse-crystalline kaolin- ite becomes less abundant, whereas the formation is only thinly preserved farther to the east in the Brorson Halvø-1 borehole (Fig. 4). Vermiculite does not occur in the succession in the Brorson Halvø-1 core, except for minor amounts in the uppermost sample from Stra- tumbjerg Formation. This is compatible with the larger distance to the submarine fault crest to the west that primarily fed vermiculite to the proximal part of the half-graben. The Palnatokes Bjerg Formation is more sedi- ment-starved than the Lindemans Bugt Formation due to transgression and waning of active rifting (Fig.  11C; Surlyk 2003). This is reflected in the high calcareous con- tent suggestive of slow clastic deposition. The presence of occasional muddy sandstones, however, implies that gravity-flow processes were still operative. In the Bror- son Halvø-1 core, chlorite occurs in the rift climax and waning rift samples, whereas it is only found in waning rift samples in the Rødryggen-1 core, and in smaller amounts (Figs 3, 4). This indicates that chlorite was sup- plied from the north-north-west by axial transport and deposited primarily in the distal part of the half-graben since the proximal part was mainly fed by the submarine fault scarp to the west. The abundance of chlorite may have resulted from erosion of the Meso–Neoprotero- zoic metamorphic rocks north-west of Wollaston For- land that were exposed due to rift faulting, since chlorite often originates from such lithologies (Nielsen et  al. 2015). The provenance signature of the Stratumbjerg Forma- tion near the Brorson Halvø-1 drill site is also indicative of a change in source area since the Archaean zircon age population is absent, in contrast to the Bernbjerg Forma- tion (Fig. 9), which signifies a change in sediment source from the crystalline rocks to the west to the metamorphic and crystalline rocks to the north-west of the half-graben. This change is not evident in the zircon age distributions of the Palnatokes Bjerg and Lindemans Bugt Formations reported by Barham et al. (2020) because their samples were taken from localities within the proximal half- graben that were linked directly to the coastline. 5.4 Diagenetic evolution Textural relationships in sediments of the Rødryggen-1 and Brorson Halvø-1 cores have been used to determine the diagenetic sequence. A diagenetic process scheme is established to highlight the relative importance of each process (Fig. 12), as discussed next. The sedimentary suc- cession in the cores has poor reservoir quality since the few sandstone intervals are thin and muddy. The reser- voir properties are poorest in the intervals with perva- sive carbonate cementation. The formation of secondary porosity by partial dissolution of bioclasts and feldspars and by fracture formation has only had a minor influence on the total porosity. The permeability is only slightly affected by the dissolution process since it was restricted to local clasts. The open fractures, however, have pre- sumably increased the permeability significantly. 5.4.1 Eogenetic processes Pyrite framboids precipitated early in the sediments in association with bacterial sulphate reduction of organic matter (Fig.  7A). The membrane of organic matter in shells probably promoted early pyrite formation within many of the bioclasts (Fig. 8A). Euhedral pyrite formed only during the rift climax, corresponding primarily to the Lindemans Bugt Formation where the largest amounts of pyrite are found (Figs 3, 4, 5C, 7B). The small euhedral crystals suggest syngenetic formation of pyrite indicating that the chemocline moved above the sediment–water interface and anoxic conditions may have prevailed during the rift climax phase (Tri- bovillard et al. 2006) or the crystals may have formed later diagenetically. Dysoxic conditions were dominant when the rifting was still at an initial stage during depo- sition of the Bernbjerg Formation, and when rifting was waning as seen by the increased bioturbation and low https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 18 of 22 GEUSBULLETIN.ORG pyrite content of the Palnatokes Bjerg and Stratumb- jerg Formations. During sulphidic bottom-water con- ditions, the reactivity and abundance of Fe minerals control the amount of pyrite that can form, whereas pyrite formation is controlled by the reactivity and abundance of organic matter during oxygenated bot- tom-water conditions (Berner 1985). Thus, the low amounts (0–1%) of total organic carbon (TOC) present in the Palnatokes Bjerg and Stratumbjerg Formations largely precluded pyrite precipitation, whereas higher TOC (2–6%) in the Bernbjerg and Lindemans Bugt For- mations (Bojesen-Koefoed et  al. 2023b, this volume) will have favoured this process. The calcite and dolomite cements probably formed shortly after deposition. The sparry carbonate cement within calpionellids in Bernbjerg and Lindemans Bugt Formations must have formed early after deposition since the calpionellids have not been deformed by mechanical compaction (Fig. 8A, B). The presence of bio- clasts is important for the precipitation of dolomite and ankerite (e.g. Hendry et al. 2000; Burns et al. 2005) since they act both as nucleation sites for the crystals and as a source of carbonate. The Palnatokes Bjerg Formation was sediment-starved so pelagic lime mud formed a sig- nificant component of the sediment that accumulated on the sea floor, and the pelagic carbonate resulted in micritic calcite matrix (Fig. 7F). In the Bernbjerg and Lindemans Bugt Formations, the laminated mudstones signify reducing conditions during deposition as also reflected in the relatively high content of organic matter. In the Palnatokes Bjerg Formation, the bioturbation intensity reveals more oxygenated depositional conditions, and many of the bioclasts were preserved in this formation (Figs 8C, D). Partial dissolution of calpionellids and other bioclasts in the Bernbjerg and Lindemans Bugt Formations resulted in carbonate-cemented layers with a large bioclast content, caused by a primary heterogeneity (Fig.  7E). These layers possibly represent bioclast concentrations produced by reworking at discrete flooding surfaces (e.g. Burns et  al. 2005). This is also suggested by the cemented mudstones that typically occur at the top of a few metres of upward-coarsening successions or in the finest grained intervals at the base of upward-coarsen- ing cycles. The fewer cemented intervals in the Linde- mans Bugt Formation in comparison to the Bernbjerg Formation (Fig. 3) are thus in accordance with the pro- gressive deepening of the setting, where the influence of minor relative sea-level fluctuations decreased steadily. 5.4.2 Mesogenetic processes The presence of authigenic mixed layer illite-smectite and illite in the studied mudstones indicates that illiti- sation of smectite has occurred, thereby providing sil- ica and cations for other mineral reactions such as the formation of quartz and ankerite (Fig.  12). Significant illitisation may, however, be contradicted by the pres- ence of K-feldspar in the investigated mudstones, as K-feldspar disappears in shales from most wells below 2.5 km in the northern North Sea due to the illitisation Fig. 12 Diagenetic process scheme of the authigenic changes that have occurred in the Rødryggen-1 and Brorson Halvø-1 successions. See Section 5.4 for explanation. Diagenetic process Sulphate reduction Bioclast alteration Smectite illitization Carbonate transformation Fracture formation Meteoric water �ushing Diagenetic regime Eogenesis Eogenesis Mesogenesis Mesogenesis Telogenesis Telogenesis Temperature depositional depositional >80°C 80–100°C <65°C <50°C Dissolution organic matter, Fe-minerals bioclasts, carbonate ooze smectite, K-feldspar dolomite, smectite bulk mudstone feldspar, mica Precipitation pyrite calcite, dolomite illite, quartz ankerite, barite opal, dolomite kaolinite Porosity decreased decreased decreased decreased increased slightly increased slightly Permeability decreased decreased decreased decreased increased decreased slightly Requirements S from seawater Mg from seawater detrital smectite Ba from initial seawater source of water supply of meteoric water Morphology https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 19 of 22 GEUSBULLETIN.ORG of smectite (Pearson & Small 1988). If the deposited clay minerals were rich in illite, however, the pore fluids may not have been undersaturated with respect to potas- sium and consequently less aggressive towards K-feld- spar during early diagenesis. Hence, K-feldspar may have survived until deep burial. The iron necessary to form ankerite may have been provided by smectite illi- tisation and it may have formed at the expense of dolo- mite cement. Barite is typically a late authigenic phase because the pore fluids need to be very concentrated before they contain sufficient Ba for barite formation. As expected, barite formed late in the studied sediments as seen by the crystal habit of barite as euhedral over- growths (Fig. 7D), and the string-like occurrence of the precipitated barite identifies the transport route of the last pore fluid. The diagenetic alteration of the mudstones is indic- ative of the maximum burial depths to which they have been exposed prior to structural inversion. The pres- ence of quartz overgrowths shows that the sediments must have been exposed to temperatures of at least c. 80°C that is necessary for the growth onset and less than c. 100°C since they are thin and scattered (Bjørlykke & Jahren 2015). Precipitation of quartz in mudstones can be sourced by the smectite to illite transformation, which generally occurs at temperatures of 60–100°C (Thyberg et al. 2009) and is likely to have happened in the studied sediments. Barite precipitated after quartz and anker- ite in the mudstones as the last mineral phase during deep burial, a process that has been found to occur at temperatures of 83–105°C in sandstones (Burley et  al. 1989). Thus, the precipitation temperatures of the auth- igenic phases that formed at deepest burial correspond to maximum burial depths of c. 2.1–2.6 km assuming a surface temperature of 20°C and a palaeogeothermal gradient of 30°C/km (Japsen et  al. 2021). This is less than the estimated uplift of c. 2.8 km based on thermo- chronological data from Upper Jurassic sediments from Jameson Land c. 450 km towards south-south-west, in which the diagenesis has progressed further (Green & Japsen 2018; Olivarius et al. 2018a). 5.4.3 Telogenetic processes The fracturing that has occurred in the sediments must have happened late during uplift since the thin fractures cross-cut the authigenic phases in the sediments. Frac- turing is presumed to have accompanied exhumation and pressure release since cooling of the sediments was necessary to decrease their elasticity enough for fractur- ing (e.g. Gale et al. 2014). The fractures formed mainly in the cemented intervals because they had least elasticity. The late timing of the fracturing is also testified by the opal infill, which requires low temperatures of <65°C for precipitation (Weibel et al. 2010). The pore fluids must have been oversaturated with silica in the beginning since opal often formed along the rim of the fractures (Fig. 8E). Formation of Fe-rich dolomite then took over in accordance with the expected composition of the pore fluid since the fractured mudstones are cemented with dolomite and ankerite. The pore fluid became depleted in Fe, so the last dolomite that precipitated was Fe-poor (Fig.  8F). The last fracturing episode happened so late during exhumation that no mineral phases were pre- cipitated in the fractures, which thus contribute minor secondary porosity. However, it is difficult to differen- tiate natural open fractures, formed in the subsurface, from artefacts produced during drilling and drying of the core. Introduction of meteoric water is a common mech- anism for kaolinite formation (Bjørlykke 1998), as this process could not take place after deposition in the marine environment. The partially dissolved feldspar grains have not been deformed so the secondary porosity has been preserved (Fig. 6D), which indicates that the dissolution and kaolinisation of detrital phases may have happened late during the exhuma- tion (Fig. 12). The fracturing that has occurred during late uplift may have caused a flow of meteoric water through the sediment that was sufficient for kaolinite formation. This may also explain why the latest gener- ation of fractures is not cemented since the pore fluids had a low saturation. 5.5 Implications for sediment composition in the Norwegian–Greenland Seaway The presence of Archaean zircon grains in the Norwe- gian Sea is often considered diagnostic of sediment supply from East Greenland since Archaean zircons are scarce in sediment eroded off the Fennoscandian Shield (e.g. Morton et al. 2008). Only a single Archaean zircon grain was retrieved from the sample from the Stratum- bjerg Formation on Wollaston Forland (Fig. 9). However, the absence or scarcity of Archaean zircons cannot be considered unambiguous proof of a Fennoscandian source in the offshore sediments. This is particularly the case in sediment derived from the central or northern part of the East Greenland Caledonides where Palae- oproterozoic basement is most abundant, whereas Archaean basement is more abundant in the southern Caledonides (Thrane 2002). This is reflected in the geo- graphical differences evident in the zircon age distribu- tions of post-Caledonian sediments in East Greenland (Sláma et al. 2011; Olivarius et al. 2018b). In sediments with an East Greenland source, the present results highlight how a high proportion of Mesoproterozoic and latest Palaeoproterozoic zircon ages testifies to a prov- enance from the southern East Greenland Caledonides, whereas a higher proportion of late Palaeoproterozoic https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 20 of 22 GEUSBULLETIN.ORG (2.0–1.7 Ga) ages is indicative of a more northern sediment source. This is reflected in the distribution of zircon age populations in sediments in the western part of the Nor- wegian Sea such as in the Upper Cretaceous – Paleocene succession (Fonneland et al. 2004; Morton et al. 2005). Time-equivalent sediments in the Norwegian Sea have presumably experienced some of the same diagenetic reactions as the studied sediments, specifically, initial sul- phate reduction causing pyrite precipitation, eogenetic bioclast alteration causing calcite-dolomite cementation, mesogenetic smectite illitisation and quartz precipitation and carbonate transformation into ankerite (Fig. 12). 6. Conclusions This study illustrates that changes in mudstone compo- sition can be induced by half-graben evolution and that the composition may also vary in relation to the position in the rift basin and the sea-bottom topography. This knowledge can be applied to predict variations in sedi- ment composition in underexplored half-graben settings. The diagenetic evolution includes processes related to the different diagenetic regimes that the mudstones have experienced. During early diagenesis, sulphate reduction caused pyrite formation, and bioclast alter- ation resulted in precipitation of calcite and dolomite. During burial diagenesis, illite and quartz formed due to smectite illitisation, and ankerite and barite precipitated because of carbonate transformation. During uplift, opal and dolomite precipitated in the earliest fractures, and kaolinite formed due to meteoric water flushing. The provenance analysis of sand-rich intervals shows that the zircon age patterns of the studied sedi- ments are most similar to other Upper Jurassic – Lower Cretaceous sandstones from East and North-East Greenland. This is revealed by MDS where it is evi- dent that the Archaean–Palaeoproterozoic crystalline basement complexes and the Meso–Neoproterozoic metasediments comprise two end members, so their derived detritus must have been mixed to produce the Mesozoic sediments. Acknowledgements Technical assistance by Helene Almind, Kirsten Fries, John Boserup, Fiorella F. Aguilera, Mojagan Alaei, Michael S. Nielsen and Jette Hal- skov is much appreciated. Valuable advice was provided by Emma Sheldon, Jon Ineson, Henrik Vosgerau, Holger Lindgreen and Tonci Balic-Zunic. The authors would like to thank the reviewers Chris Kirk- land and Kevin Taylor for insightful comments that helped improve the manuscript. Additional information Funding statement Funding for drilling of the Rødryggen-1 and Brorson Halvø-1 bore- holes and studies of the cores was provided by a consortium of oil companies and the Geological Survey of Denmark and Greenland (GEUS). Author contributions MO: wrote the manuscript in cooperation with the other authors. MO, AK, RW: performed the mineralogical and petrographic work. TK: processed the radiometric analyses. JH: carried out the sedimentological work. Competing interests None. Additional files: The full table of zircon U-Pb data is provided as Supplementary File S1, available at https://doi.org/10.22008/FK2/KEL0A6. References Alsen, P., Piasecki, S., Nøhr-Hansen, H., Pauly, S., Sheldon, E. & Hovikoski, J. 2023: Stratigraphy of the Upper Jurassic to lowermost Cretaceous in the Rødryggen-1 and Brorson Halvø-1 boreholes, Wollaston Forland, North-East Greenland. GEUS Bulletin 55, 8342 (this volume). https:// doi.org/10.34194/geusb.v55.8342 Barham, M., Kirkland, C.L., Hovikoski, J., Alsen, P., Hollis, J. & Tyrrell, S. 2020: Reduce or recycle? Revealing source to sink links through inte- grated zircon–feldspar provenance fingerprinting. Sedimentology 68, 531–556. https://doi.org/10.1111/sed.12790 Berner, R.A. 1985: Sulphate reduction, organic matter decomposition and pyrite formation. Royal Society of London, Series A 315, 25–38. https://doi.org/10.1098/rsta.1985.0027 Bjerager, M. et  al. 2020: Cretaceous lithostratigraphy of North-East Greenland. Bulletin of the Geological Society of Denmark 68, 37–93. https://doi.org/10.37570/bgsd-2020-68-04 Bjørlykke, K. 1998: Clay mineral diagenesis in sedimentary basins – a key to the prediction of rock properties. Examples from the North Sea Basin. Clay Minerals 33, 15–34. https://doi.org/10.1180/claymin.1998.033.1.03 Bjørlykke, K. & Jahren, J. 2015: Sandstones and Sandstone Reservoirs. In: Bjørlykke, K. (ed.): Petroleum Geoscience: From Sedimentary Environ- ments to Rock Physics 119–149. Berlin, Heidelberg: Springer. https:// doi.org/10.1007/978-3-642-34132-8_4 Bojesen-Koefoed, J.A., Alsen, P., Bjerager, M., Hovikoski, J., Ineson, J.R., Johannessen, P.N., Olivarius, M., Piasecki, S. & Vosgerau, H. 2023a: The Rødryggen-1 and Brorson Halvø-1 fully cored boreholes (Upper Jurassic – Lower Cretaceous), Wollaston Forland, North-East Greenland – an introduction. GEUS Bulletin 55, 8350 (this volume). https://doi.org/10.34194/geusb.v55.8350 Bojesen-Koefoed, J.A., Alsen, P., Bjerager, M., Hovikoski, J., Johannes- sen, P.N., Nøhr-Hansen, H., Petersen, H.I., Piasecki, S. & Vosgerau, H. 2023b: Organic geochemistry of an Upper Jurassic – Lower Cre- taceous mudstone succession in a narrow graben setting, Wollaston Forland Basin, North-East Greenland. GEUS Bulletin 55, 8320 (this vol- ume). https://doi.org/10.34194/geusb.v55.8320 Burley, S.D., Mullis, J. & Matter, A. 1989: Timing diagenesis in the Tartan reservoir (UK North Sea): Constraints from com- bined cathodoluminescence microscopy and fluid inclusion studies. Marine and Petroleum Geology 6, 98–120. https://doi. org/10.1016/0264-8172(89)90014-7 Burns, F.E., Burley, S.D., Gawthorpe, R.L. & Pollard, J.E. 2005: Diagenetic signatures of stratal surfaces in the Upper Jurassic Fulmar Formation, Central North Sea, UKCS. Sedimentology 52, 1155–1185. https://doi. org/10.1111/j.1365-3091.2005.00729.x Dhuime, B., Bosch, D., Bruguier, O., Caby, R. & Pourtales, S. 2007: Age, provenance and post-deposition metamorphic overprint of detrital zircons from the Nathorst Land group (NE Greenland) – A LA-ICP-MS and SIMS study. Precambrian Research 155, 24–46. https://doi. org/10.1016/j.precamres.2007.01.002 Dröllner, M., Barham, M., Kirkland, C.L. & Ware, B. 2021: Every zircon deserves a date: Selection bias in detrital geochronology. Geological Magazine 158, 1135–1142. https://doi.org/10.1017/S0016756821000145 Elvevold, S., Thrane, K. & Gilotti, J.A. 2003: Metamorphic his- tory of high-pressure granulites in Payer Land, Greenland https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ https://doi.org/10.22008/FK2/KEL0A6 https://doi.org/10.34194/geusb.v55.8342 https://doi.org/10.34194/geusb.v55.8342 https://doi.org/10.1111/sed.12790 https://doi.org/10.1098/rsta.1985.0027 https://doi.org/10.37570/bgsd-2020-68-04 https://doi.org/10.1180/claymin.1998.033.1.03 https://doi.org/10.1007/978-3-642-34132-8_4 https://doi.org/10.1007/978-3-642-34132-8_4 https://doi.org/10.34194/geusb.v55.8350 https://doi.org/10.34194/geusb.v55.8320 https://doi.org/10.1016/0264-8172(89)90014-7 https://doi.org/10.1016/0264-8172(89)90014-7 https://doi.org/10.1111/j.1365-3091.2005.00729.x https://doi.org/10.1111/j.1365-3091.2005.00729.x https://doi.org/10.1016/j.precamres.2007.01.002 https://doi.org/10.1016/j.precamres.2007.01.002 https://doi.org/10.1017/S0016756821000145 Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 21 of 22 GEUSBULLETIN.ORG Caledonides. Journal of Metamorphic Geology 21, 49–63. https://doi. org/10.1046/j.1525-1314.2003.00419.x Fonneland, H.C., Lien, T., Martinsen, O.J., Pedersen, R.B. & Košler, J. 2004: Detrital zircon ages: A key to understanding the deposition of deep marine sandstones in the Norwegian Sea. Sedimentary Geology 164, 147–159. https://doi.org/10.1016/j.sedgeo.2003.09.005 Gale, J.F.W., Laubach, S.E., Olson, J.E., Eichhubl, P. & Fall, A. 2014: Natural fractures in shale: A review and new observations. AAPG Bulletin 98, 2165–2216. https://doi.org/10.1306/08121413151 Gawthorpe, R.L. & Leeder, M.R. 2000: Tectono- sedimentary evolution of active extensional basins. Basin Research 12, 195–218. https://doi. org/10.1111/j.1365-2117.2000.00121.x Gilotti, J.A., Jones, K.A. & Elvevold, S. 2008: Caledonian metamorphic patterns in Greenland. Geological Society of America Memoir 202, 201–225. https://doi.org/10.1130/2008.1202(08) Green, P.F. & Japsen, P. 2018: Burial and exhumation history of the Jameson Land Basin, East Greenland, estimated from thermochrono- logical data from the Blokelv-1 core. Geological Survey of Denmark and Greenland Bulletin 42, 133–147. https://doi.org/10.34194/geusb. v42.4324 Hendry, J.P., Wilkinson, M., Fallick, A.E. & Haszeldine, R.S. 2000: Anker- ite cementation in deeply buried Jurassic sandstone reservoirs of the Central North Sea. Journal of Sedimentary Research 70, 227–239. https://doi.org/10.1306/2DC4090D-0E47-11D7-8643000102C1865D Henriksen, N. & Higgins, A.K. 2008: Geological research and mapping in the Caledonian orogen of East Greenland, 70°N–82°N. In: Higgins, A.K. et al. (eds): The Greenland Caledonides: Evolution of the North- east Margin of Laurentia. Geological Society of America Memoirs 202, 1–27. Henriksen, N., Higgins, A.K., Gilotti, J.A. & Smith, M.P. 2008: Introduction – The Caledonides of Greenland. The Geological Society of America, Memoir 202, v–xv. https://doi.org/10.1130/2008.1202(00) Henstra, G.A. et al. 2016: Depositional processes and stratigraphic archi- tecture within a coarse-grained rift-margin turbidite system: The Wollaston Forland Group, east Greenland. Marine and Petroleum Geology 76, 187–209. https://doi.org/10.1016/j.marpetgeo.2016.05.018 Higgins, A.K. et al. 2004: The foreland-propagating thrust architecture of the East Greenland Caledonides 72°–75°N. Journal of the Geological Society 161, 1009–1026. https://doi.org/10.1144/0016-764903-141 Hillier, S. 2000: Accurate quantitative analysis of clay and other minerals in sandstones by XRD: comparison of a Rietveld and a reference inten- sity ratio (RIR) method and the importance of sample preparation. Clay Minerals 35, 291–302. https://doi.org/10.1180/000985500546666 Hovikoski, J., Uchman, A., Alsen, P. & Ineson, J. 2018: Ichnological and sedimentological characteristics of submarine fan-delta deposits in a half-graben, Lower Cretaceous Palnatokes Bjerg Formation, NE Greenland. Ichnos 26(1), 28–57. https://doi.org/10.1080/10420940.20 17.1396981 Hovikoski, J., Ineson, J.R., Olivarius, M., Bojesen-Koefoed, J.A., Piasecki, S. & Alsen, P. 2023a: Upper Jurassic – Lower Cretaceous of eastern Wollaston Forland, North-East Greenland: a distal marine record of an evolving rift. GEUS Bulletin 55, 8349 (this volume). https://doi. org/10.34194/geusb.v55.8349 Hovikoski, J. et al. 2023b: Late Jurassic – Early Cretaceous marine deox- ygenation in NE Greenland. Journal of the Geological Society 180, jgs2022–058. https://doi.org/10.1144/jgs2022-058 Jackson, S.E., Pearson, N.J., Griffin, W.L. & Belousova, E.A. 2004: The application of laser ablation-inductively coupled plasma-mass spec- trometry to in situ U–Pb zircon geochronology. Chemical Geology 211, 47–69. https://doi.org/10.1016/j.chemgeo.2004.06.017 Japsen, P., Green, P.F., Bonow, J.M., Bjerager, M. & Hopper, J.R. 2021: Episodic burial and exhumation in North-East Greenland before and after opening of the North-East Atlantic. GEUS Bulletin 45(2). 5299. https://doi.org/10.34194/geusb.v45.5299 Kalsbeek, F., Nutman, A.P. & Taylor, P.N. 1993: Palaeoprotero- zoic basement province in the Caledonian fold belt of North- East Greenland. Precambrian Research 63, 163–178. https://doi. org/10.1016/0301-9268(93)90010-Y Kalsbeek, F., Thrane, K., Nutman, A.P. & Jepsen, H.F. 2000: Late Meso- proterozoic to early Neoproterozoic history of the East Greenland Caledonides: Evidence for Grenvillian orogenesis? Journal of the Geological Society (London) 157, 1215–1225. https://doi.org/10.1144/ jgs.157.6.1215 Kalsbeek, F., Jepsen, H.F. & Nutman, A.P. 2001: From source migma- tites to plutons: Tracking the origin of ca. 435 Ma S-type granites in the East Greenland Caledonian orogen. Lithos 57, 1–21. https://doi. org/10.1016/S0024-4937(00)00071-2 Kalsbeek, F., Thrane, K., Higgins, A.K., Jepsen, H.F., Leslie, A.G., Nutman, A.P. & Frei, R. 2008a: Polyorogenic history of the East Greenland Cale- donides. Geological Society of America Memoir 202, 55–72. Kalsbeek, F., Higgins, A.K., Jepsen, H.F., Frei, R. & Nutman, A.P. 2008b: Granites and granites in the East Greenland Caledonides. Geo- logical Society of America Memoir 202, 227–249. https://doi. org/10.1130/2008.1202(09) Langrock, U., Stein, R., Lipinski, M. & Brumsack, H.-J. 2003: Late Jurassic to Early Cretaceous black shale formation and paleoenvironment in high northern latitudes: Examples from the Norwegian-Greenland Seaway. Paleoceanography 18, 1074. https://doi.org/10.1029/2002PA000867 Larsen, P.-H., Olsen, H. & Clack, J.A. 2008: The Devonian basin in East Greenland – Review of basin evolution and vertebrate assemblages. Geological Society of America Memoir 202, 273–292. https://doi. org/10.1130/2008.1202(11) Leslie, A.G. & Nutman, A.P. 2003: Evidence for Neoproterozoic orogen- esis and early high temperature Scandian deformation events in the southern East Greenland Caledonides. Geological Magazine 140, 309–333. McCusker, L.B., Von Dreele, R.B., Cox, D.E., Louer, D. & Scardi, P. 1999: Rietveld refinement guidelines. Journal of Applied Crystallography 32, 36–50. https://doi.org/10.1107/S0021889898009856 McKerrow, W.S., Mac Niocaill, C. & Dewey, J.F. 2000: The Caledonian Orogeny redefined. Journal of the Geological Society (London) 157, 1149–1154. https://doi.org/10.1144/jgs.157.6.1149 Morton, A.C., Whitham, A.G. & Fanning, C.M. 2005: Provenance of Late Cretaceous to Paleocene submarine fan sandstones in the Norwe- gian Sea: Integration of heavy mineral, mineral chemical and zircon age data. Sedimentary Geology 182, 3–28. https://doi.org/10.1016/j. sedgeo.2005.08.007 Morton, A., Fanning, M. & Milner, P. 2008: Provenance characteristics of Scandinavian basement terrains: Constraints from detrital zircon ages in modern river sediments. Sedimentary Geology 210, 61–85. Mutterlose, J. et al. 2003: The Greenland-Norwegian Seaway: A key area for understanding Late Jurassic to Early Cretaceous paleoenvironments. Paleoceanography 18, 1010. https://doi.org/10.1029/2001PA000625 Nielsen, O.B., Rasmussen, E.S. & Thyberg, B.I. 2015: Distribution of clay min- erals in the northern North Sea Basin during the Paleogene and Neo- gene: A result of source-area geology and sorting processes. Journal of Sedimentary Research 85, 562–581. https://doi.org/10.2110/jsr.2015.40 Nøhr-Hansen, H., Piasecki, S. & Alsen, P. 2020: A Cretaceous dinoflagel- late cyst zonation for NE Greenland. Geological Magazine 157, 1658– 1692. https://doi.org/10.1017/S0016756819001043 Olierook, H.K.H., Barham, M., Kirkland, C.L., Hollis, J. & Vass, A. 2020: Zircon fingerprint of the Neoproterozoic North Atlantic: Perspectives from East Greenland. Precambrian Research 342, 105653. https://doi. org/10.1016/j.precamres.2020.105653 Olivarius, M., Weibel, R., Schovsbo, N.H., Olsen, D. & Kjøller, C. 2018a: Diagenesis of Upper Jurassic sandstones of the Blokelv-1 core in the Jameson Land Basin, East Greenland. Geological Survey of Denmark and Greenland Bulletin 42, 65–84. https://doi.org/10.34194/geusb.v42.4310 Olivarius, M., Bjerager, M., Keulen, N., Knudsen, C. & Kokfelt, T.F. 2018b: Provenance of basinal sandstones in the Upper Jurassic Hareelv Formation, Jameson Land Basin, East Greenland. Geological Sur- vey of Denmark and Greenland Bulletin 42, 115–126. https://doi. org/10.34194/geusb.v42.4317 Pearson, M.J. & Small, J.S. 1988: Illite–smectite diagenesis and palaeo- temperatures in northern North Sea Quaternary to Mesozoic shale sequences. Clay Minerals 23, 109–132. https://doi.org/10.1180/ claymin.1988.023.2.01 Piasecki, S., Bojesen-Koefoed, J.A. & Alsen, P. 2020: Geology of the Lower Cretaceous in the Falkebjerg area, Wollaston Forland, northern East Greenland. Bulletin of the Geological Society of Denmark 68, 155–170. https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ https://doi.org/10.1046/j.1525-1314.2003.00419.x https://doi.org/10.1046/j.1525-1314.2003.00419.x https://doi.org/10.1016/j.sedgeo.2003.09.005 https://doi.org/10.1306/08121413151 https://doi.org/10.1111/j.1365-2117.2000.00121.x https://doi.org/10.1111/j.1365-2117.2000.00121.x https://doi.org/10.1130/2008.1202(08 https://doi.org/10.34194/geusb.v42.4324 https://doi.org/10.34194/geusb.v42.4324 https://doi.org/10.1306/2DC4090D-0E47-11D7-8643000102C1865D https://doi.org/10.1130/2008.1202(00 https://doi.org/10.1016/j.marpetgeo.2016.05.018 https://doi.org/10.1144/0016-764903-141 https://doi.org/10.1180/000985500546666 https://doi.org/10.1080/10420940.2017.1396981 https://doi.org/10.1080/10420940.2017.1396981 https://doi.org/10.34194/geusb.v55.8349 https://doi.org/10.34194/geusb.v55.8349 https://doi.org/10.1144/jgs2022-058 https://doi.org/10.1016/j.chemgeo.2004.06.017 https://doi.org/10.34194/geusb.v45.5299 https://doi.org/10.1016/0301-9268(93)90010-Y https://doi.org/10.1016/0301-9268(93)90010-Y https://doi.org/10.1144/jgs.157.6.1215 https://doi.org/10.1144/jgs.157.6.1215 https://doi.org/10.1016/S0024-4937(00)00071-2 https://doi.org/10.1016/S0024-4937(00)00071-2 https://doi.org/10.1130/2008.1202(09 https://doi.org/10.1130/2008.1202(09 https://doi.org/10.1029/2002PA000867 https://doi.org/10.1130/2008.1202(11 https://doi.org/10.1130/2008.1202(11 https://doi.org/10.1107/S0021889898009856 https://doi.org/10.1144/jgs.157.6.1149 https://doi.org/10.1016/j.sedgeo.2005.08.007 https://doi.org/10.1016/j.sedgeo.2005.08.007 https://doi.org/10.1029/2001PA000625 https://doi.org/10.2110/jsr.2015.40 https://doi.org/10.1017/S0016756819001043 https://doi.org/10.1016/j.precamres.2020.105653 https://doi.org/10.1016/j.precamres.2020.105653 https://doi.org/10.34194/geusb.v42.4310 https://doi.org/10.34194/geusb.v42.4317 https://doi.org/10.34194/geusb.v42.4317 https://doi.org/10.1180/claymin.1988.023.2.01 https://doi.org/10.1180/claymin.1988.023.2.01 Olivarius et al. 2023: GEUS Bulletin 55. 8309. https://doi.org/10.34194/geusb.v55.8309 22 of 22 GEUSBULLETIN.ORG Rateev, M.A., Sadchikova, T.A. & Shabrova, V.P. 2008: Clay minerals in recent sediments of the world ocean and their relation to types of lithogenesis. Lithology and Mineral Resources 43, 125–135. https://doi.org/10.1134/S002449020802003X Rietveld, H.M. 1969: A profile refinement method for nuclear and mag- netic structures. Journal of Applied Crystallography 2, 65–71. https:// doi.org/10.1107/S0021889869006558 Rogov, M.A., Shchepetova, E.V. & Zakharov, V.A. 2020: Late Jurassic – Earliest Cretaceous prolonged shelf dysoxic–anoxic event and its possible causes. Geological Magazine 157, 1622–1642. https://doi. org/10.1017/S001675682000076X Sambridge, M. & Lambert, D.D. 1997: Propagating errors in decay equa- tions: Examples from the Re-Os isotopic system. Geochimica et Cos- mochimica Acta 61, 3019–3024. Sláma, J. & Košler, J. 2012: Effects of sampling and mineral separation on accuracy of detrital zircon studies. Geochemistry, Geophysics, Geosystems 13, Q05007. https://doi.org/10.1029/2012GC004106 Sláma, J. et al. 2008: Plešovice zircon – A new natural reference material for U–Pb and Hf isotopic microanalysis. Chemical Geology 249, 1–35. https://doi.org/10.1016/j.chemgeo.2007.11.005 Sláma, J., Walderhaug, O., Fonneland, H., Kosler, J. & Pedersen, R.B. 2011: Provenance of Neoproterozoic to upper Cretaceous sedimentary rocks, eastern Greenland: Implications for recognizing the sources of sediments in the Norwegian Sea. Sedimentary Geology 238, 254–267. https://doi.org/10.1016/j.sedgeo.2011.04.018 Slater, C. & Cohen, L. 1962: A centrifugal particle size analyser. Journal of Scientific Instrumentation 39, 614–617. Smith, M.P. & Rasmussen, J.A. 2008: Cambrian–Silurian development of the Laurentian margin of the Iapetus Ocean in Greenland and related areas. Geological Society of America Memoir 202, 137–167. https://doi.org/10.1130/2008.1202(06) Stacey, J.S. & Kramers, J.D. 1975: Approximation of terrestrial lead iso- tope evolution by a two-stage model. Earth and Planetary Science Let- ters 26, 207–221. https://doi.org/10.1016/0012-821X(75)90088-6 Stemmerik, L., Christensen, F.G., Piasecki, S., Jordt, B., Marcussen, C. & Nøhr-Hansen, H. 1992: Depositional history and petroleum geology of the Carboniferous to Cretaceous sediments in the northern part of East Greenland. Norwegian Petroleum Federation, Special Publi- cation 2, 67–87. https://doi.org/10.1016/B978-0-444-88943-0.50009-5 Stemmerik, L., Clausen, O.R., Korstgård, J., Larsen, M., Piasecki, S., Seidler, L., Surlyk, F. & Therkelsen, J. 1997: Petroleum geological investigations in East Greenland: Project ‘Resources of the sedimentary basins of North and East Greenland’. Geological Survey of Greenland Bulletin 176, 29–38. https://doi.org/10.34194/ggub.v176.5058 Stoker, M.S. et al. 2017: An overview of the Upper Palaeozoic–Mesozoic stratigraphy of the NE Atlantic region. Geological Society, London, Special Publications 447, 11–68. https://doi.org/10.1144/SP447.2 Strachan, R.A., Nutman, A.P. & Friderichsen, J.D. 1995: SHRIMP U-Pb geo- chronology and metamorphic history of the Smallefjord sequence, NE Greenland Caledonides. Journal of the Geological Society 152, 779–784. Surlyk, F. 1978: Submarine fan sedimentation along fault scarps on tilted fault blocks (Jurassic–Cretaceous boundary, East Greenland). Geologi- cal Survey of Greenland Bulletin 128, 108 pp. https://doi.org/10.34194/ bullggu.v128.6670 Surlyk, F. 1984: Fan-delta to submarine fan conglomerates of the Volgian-Valanginian Wollaston Forland Group, East Greenland. Cana- dian Society of Petroleum Geologists Memoir 10, 359–382. Surlyk, F. 1990: A Jurassic sea-level curve for East Greenland. Palaeo- geography, Palaeoclimatology, Palaeoecology 78, 71–85. https://doi. org/10.1016/0031-0182(90)90205-L Surlyk, F. 2003: The Jurassic of East Greenland: A sedimentary record of thermal subsidence, onset and culmination of rifting. Geological Survey of Denmark and Greenland Bulletin 1, 659–722. https://doi. org/10.34194/geusb.v1.4674 Surlyk, F. & Korstgård, J. 2013: Crestal unconformities on an exposed Jurassic tilted fault block, Wollaston Forland, East Greenland as an analogue for buried hydrocarbon traps. Marine and Petroleum Geology 44, 82–95. https://doi.org/10.1016/j. marpetgeo.2013.03.009 Surlyk, F. et al. 2021: Jurassic stratigraphy of East Greenland. GEUS Bulle- tin 46, 6521. https://doi.org/10.34194/geusb.v46.6521 Thrane, K. 2002: Relationships between Archaean and Palaeo- proterozoic crystalline basement complexes in the southern part of the East Greenland Caledonides: An ion microprobe study. Precambrian Research 113, 19–42. https://doi.org/10.1016/ S0301-9268(01)00198-X Thyberg, B., Jahren, J., Winje, T., Bjørlykke, K. & Faleide, J.I. 2009: From mud to shale: Rock stiffening by micro-quartz cementation. First Break 27, 27–33. https://doi.org/10.3997/1365-2397.2009003 Tribovillard, N., Algeo, T.J., Lyons, T. & Riboulleau, A. 2006: Trace metals as paleoredox and paleoproductivity proxies: An update. Chemical Geology 232, 12–32. https://doi.org/10.1016/j. chemgeo.2006.02.012 Vermeesch, P. 2012: On the visualisation of detrital age distributions. Chemical Geology 312–313, 190–194. https://doi.org/10.1016/j. chemgeo.2012.04.021 Vermeesch, P., Resentini, A. & Garzanti, E. 2016: An R package for statisti- cal provenance analysis. Sedimentary Geology 336, 14–25. https://doi. org/10.1016/j.sedgeo.2016.01.009 Watt, G.R., Kinny, P.D. & Friderichsen, J.D. 2000: U–Pb geochronology of Neoproterozoic and Caledonian tectonothermal events in the East Greenland Caledonides. Journal of the Geological Society 157, 1031–1048. https://doi.org/10.1144/jgs.157.5.1031 Weibel, R., Friis, H., Kazerouni, A.M., Svendsen, J.B., Stokkendal, J. & Poulsen, M.L.K. 2010: Development of early diagenetic silica and quartz morphologies. Sedimentary Geology 228, 151–170. https://doi. org/10.1016/j.sedgeo.2010.04.008 https://doi.org/10.34194/geusb.v55.8309 http://www.geusbulletin.org/ https://doi.org/10.1134/S002449020802003X https://doi.org/10.1107/S0021889869006558 https://doi.org/10.1107/S0021889869006558 https://doi.org/10.1017/S001675682000076X https://doi.org/10.1017/S001675682000076X https://doi.org/10.1029/2012GC004106 https://doi.org/10.1016/j.chemgeo.2007.11.005 https://doi.org/10.1016/j.sedgeo.2011.04.018 https://doi.org/10.1130/2008.1202(06 https://doi.org/10.1016/0012-821X(75)90088-6 https://doi.org/10.1016/B978-0-444-88943-0.50009-5 https://doi.org/10.34194/ggub.v176.5058 https://doi.org/10.1144/SP447.2 https://doi.org/10.34194/bullggu.v128.6670 https://doi.org/10.34194/bullggu.v128.6670 https://doi.org/10.1016/0031-0182(90)90205-L https://doi.org/10.1016/0031-0182(90)90205-L https://doi.org/10.34194/geusb.v1.4674 https://doi.org/10.34194/geusb.v1.4674 https://doi.org/10.1016/j.marpetgeo.2013.03.009 https://doi.org/10.1016/j.marpetgeo.2013.03.009 https://doi.org/10.34194/geusb.v46.6521 https://doi.org/10.1016/S0301-9268(01)00198-X https://doi.org/10.1016/S0301-9268(01)00198-X https://doi.org/10.3997/1365-2397.2009003 https://doi.org/10.1016/j.chemgeo.2006.02.012 https://doi.org/10.1016/j.chemgeo.2006.02.012 https://doi.org/10.1016/j.chemgeo.2012.04.021 https://doi.org/10.1016/j.chemgeo.2012.04.021 https://doi.org/10.1016/j.sedgeo.2016.01.009 https://doi.org/10.1016/j.sedgeo.2016.01.009 https://doi.org/10.1144/jgs.157.5.1031 https://doi.org/10.1016/j.sedgeo.2010.04.008 https://doi.org/10.1016/j.sedgeo.2010.04.008 Mudstone diagenesis and sandstone provenance in an Upper Jurassic – Lower Cretaceous evolving half-graben system, Wollaston Forland, North-East Greenland 1. Introduction 2. Geological setting 3. Methodology 3.1 Petrography 3.2 Zircon U-Pb geochronology 4. Results 4.1 Lithology 4.2 Detrital components 4.3 Authigenic minerals 4.4 Bioclasts 4.5 Fractures 4.6 Zircon U-Pb ages 5. Discussion 5.1 Provenance analysis 5.2 Sediment transport 5.3 Tectonic regime 5.4 Diagenetic evolution 5.4.1 Eogenetic processes 5.4.2 Mesogenetic processes 5.4.3 Telogenetic processes 5.5 Implications for sediment composition in the Norwegian-Greenland Seaway 6. Conclusions Acknowledgements Additional information References Figures Fig. 1 Geological map of North-East Greenland based on Stemmerik et al. (1997), Henriksen et al. (2008) and Kalsbeek et al. (2008a). Detailed map of Wollaston Fig. 2 Stratigraphic scheme with vertical lines showing the Rødryggen-1 (RØ-1) and Brorson Halvø-1 (BH-1) cored successions. Al: Albrechts Bugt Mb. B: Bernbjerg Fm. Ba: Bastians Dal Fm. J: Jakobsstigen Fm. L: Laugeites Ravine Mb. Li: Lindemans Bugt Formation. Li (S): Lindemans Bugt Fm (Storsletten Mb). Mu: Muslingebjerg Fm. N: Niesen Mb. Pa: Palnatokes Fig. 3 Mineralogy from XRD of the Rødryggen-1 core plotted with the sedimentological log. Chronostratigraphy from Alsen et al. (2023, this volume). See Fig. 4 for legend. Chronostrat.: chronostratigraphy. Lithostrat.: lithstratigraphy. GR: gamma ray. API: American Petroleum Units. Fig. 4 Mineralogy from XRD of the Brorson Halvø-1 core shown alongside the sedimentological log. Chronostratigraphy from Alsen et al. (2023, this volume). Chronostrat.: chronostratigraphy. Lithostrat.: lithstratigraphy. GR: gamma ray. API: American Petroleum Units. Fig. 5 Core photos of the mudstone texture of cemented versus uncemented mudstones. BH-1: Brorson Halvø-1 core. RØ-1: Rødryggen-1 core. A: Laminated sandy mudstone. B: Cemented mudstone. C: Laminated pyritic mudstone. D: Bioturbated mudstone. E: Bioclastic hematitic cemented mudstone. F: Bioturbated mudstone. Fig. 6 Texture and detrital phases. A: Typical mudstone texture. B: Cemented mudstone texture. C: Quartz occurs as silt- and sand-sized grains in the mudstones. D: Partially dissolved albite grain. E: Apatite occurs as detrital clasts. F: Most clay minerals are detrital such as chlorite. Fig. 7 Authigenic minerals. A: Framboidal pyrite has often formed in connection with organic matter. B: Euhedral pyrite has only formed in Lindemans Bugt Formation where it has overgrown pyrite framboids. C: Quartz has overgrown detrital kaolinite. D: Barite has overgrown ankerite rhombs. E: Dolomite is the dominant carbonate cement in Bernbjerg and Lindemans Bugt Formations. F: Calcite is the dominant carbonate cement in Palnatokes Bjerg Formation. See Fig. 6 for abbreviations. Fig. 8 Bioclasts and fracture fillings. A–B: Recrystallised calpionellids filled with combinations of calcite, dolomite, ankerite and pyrite, and occasionally with internal porosity. Calpionellids are present in Bernbjerg and Lindemans Bugt Formations. C–D: Well-preserved calcispheres filled with calcite and small ankerite rhombs. Calcispheres are present in Palnatokes Bjerg Formation. E: Opal precipitated in several zones in a fracture and succeeded by dolomite, which has replaced some opal along the contact (arrow). F: Opal along fracture rims and succeeded by dolomite with lower Fe content in the middle. Fractures are most abundant in Bernbjerg Formation. See Fig. 6 for abbreviations. Fig. 9 Zircon U-Pb age distributions of the Upper Jurassic – Lower Cretaceous sediments (1–4) compared to selected zircon ages from the region (A–G: Strachan et al. 1995; Watt et al. 2000; Thrane 2002; Elvevold et al. 2003; Kalsbeek et al. 1993; Leslie & Nutman 2003; Sláma et al. 2011; Olivarius et al. 2018b; Barham et al. 2020; Olierook et al. 2020). The Phanerozoic zircon ages in A–C are from the intruded Caledonian granites. The sampling locations are shown in Fig. 1. The ages are plotted using kernel density estimation (Vermeesch 2012) and histograms with a bin interval of 25 million years. Zircon ages with <10% discordancy are plotted. “n/N” denotes the number of concordant analyses out of the total number of analyses. See Fig. 1 for locations. Fig. 10 Multidimensional scaling (MDS) diagram of zircon U-Pb age data. Plotted using Kolmogorov-Smirnov (K-S) dissimilarity (Vermeesch et al. 2016). The nearest neighbours in K-S space are shown by solid lines and the second nearest by dashed lines. See Fig. 10 for sample information. Fig. 11 Inferred structural setting of northern Wollaston Forland in Late Jurassic to Early Cretaceous time when submarine deposition of mudstones Fig. 12 Diagenetic process scheme of the authigenic changes that have occurred in the Rødryggen-1 and Brorson Halvø-1 successions. See Section 5.4 for explanation.