Geological Survey of Denmark and Greenland Bulletin 6, 41-56 41Geological Survey of Denmark and Greenland Bulletin 6, 41–56 © GEUS, 2004 The Caledonian thin-skinned thrust belt of Kronprins Christian Land, eastern North Greenland A.K. Higgins, N.J. Soper, M. Paul Smith and Jan A. Rasmussen Kronprins Christian Land in the extreme north of the East Greenland Caledonides, exposes a thin-skinned thrust belt up to 50 km wide developed in Ordovician–Silurian platform lime- stones and dolostones of the Iapetus passive margin. This thrust belt is characterised by a series of SSW–NNE-trending and east-dipping Caledonian thrusts with westward displacements of generally a few kilometres each. It passes westwards into undisturbed autochthonous foreland. Based on a line and area restoration, total displacement along a well-exposed WNW–ESE sec- tion through the thrust belt amounts to 17.6 km, which represents a shortening of 45% in the line of section. Biostratigraphic control in the limestone and dolostone succession is based on conodonts and macrofossils. The alteration colours of the conodonts provide estimates of maximum burial temperatures, which show that the thickness of the overlying thrust sheets ranged from about 6 to 12.5 km from west to east across the thrust belt. Since the estimated former thickness of the Vandredalen thrust sheet above the thin-skinned parautochthonous thrust belt is insufficient to yield the temperatures attained, higher thrust sheets must once have extended across the region. Keywords: Caledonides, conodonts, Greenland, Ordovician, thrust tectonics A.K.H. & J.A.R., Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: akh@geus.dk N.J.S., Gams Bank, Threshfield, Skipton BD23 5NP, UK. Also affiliated with: Department of Geology, University College, Galway, Ireland. M.P.S., Lapworth Museum, School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. The East Greenland Caledonides extend for 1300 km along the coastal region of East Greenland between latitudes 70° and 82°N, in a belt up to 300 km wide. It can be broadly divided into an eastern thick-skinned thrust belt, and a western marginal thrust belt that in places is thin-skinned (Fig. 1). The western marginal thrust belt is characterised by the presence of fore- land windows, in most of which a thin Lower Palaeo- zoic sequence is preserved beneath the bordering thrusts demonstrating that the thrusting episode is post- Ordovician (Higgins et al. 2001a). The thrust sheets overlying the foreland windows incorporate substan- tial units of reworked basement gneisses, derived from the thick-skinned thrust belt to the east. The Green- land Inland Ice obscures the western parts of the marginal thrust belt along most of its length, and the transition between the Caledonian orogenic belt and the autochthonous foreland is only completely ex- posed in Kronprins Christian Land (79°30′–82°N). Here the transition zone takes the form of a thin-skinned parautochthonous thrust belt, which is the subject of this paper. GEUS Bulletin 6.pmd 10-02-2005, 09:5441 42 ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ C A L E D O N ID E S Greenland 70ºN 74ºN 78ºN 82ºW 35ºW Wandel Sea Centrumsø 100 km Jameson Land Scoresby Sund 25 W Traill Ø Wollaston Forland Bessel Fjord Danmarkshavn Lambert Land Peary Land Station Nord K ro np rin s C hr ist ian L an d Nørreland window Kronprins Christian Land thin-skinned thrust belt (parautochthonous foreland) Palaeogene basalts Palaeogene intrusions Wandel Sea Basin: Carboniferous–Palaeogene sediments East Greenland basins: Carboniferous–Cretaceous sediments Devonian – continental sediments Late to post-kinematic granites Neoproterozoic–Ordovician sediments (East Greenland) Neoproterozoic–Silurian sediments (eastern North Greenland) Palaeo-Mesoproterozoic sediments and basalts (eastern North Greenland) Crystalline complexes and sediments (Archaean–Mesoproterozoic) Neoproterozoic–Silurian sediments (North Greenland) Palaeo-Mesoproterozoic sediments and basalts (eastern North Greenland) Mainly crystalline rocks – parautochthonous windows Thrust Fault/shear zone Tectonic zone boundary POST-CALEDONIAN LATE TO POST-CALEDONIAN CALEDONIAN OROGENIC BELT CALEDONIAN FORELAND ▲ ▲ Fig. 2 Hamberg Gletscher foreland Dronning Louise Land Charcot Land window Målebjerg window Gåseland window C A LE D O N IA N SO LE T H R U ST IN LA N D IC E M A R G IN A L T H R U S T B E L T T H IC K S K IN N E D T H R U S T B E L T Eleonore Sø window ▲ ▲ ▲ Fig. 1. General geological map of the East Greenland Caledo- nides, illustrating the division into western marginal and eastern thick-skinned thrust belts (modified from Higgins et al. 2001a). The main foreland windows along the length of the fold belt are shown, with the Kronprins Christian Land area in the extreme north. The frame indicates the area of Fig. 2. GEUS Bulletin 6.pmd 10-02-2005, 09:5442 43 Geological setting Throughout most of its length, the East Greenland Caledonides are dominated by crystalline orthogneiss complexes (Fig. 1) that retain much of their ‘base- ment’ character despite Caledonian reworking. The protolith age of the orthogneisses has been determined as Archaean or Proterozoic on the basis of numerous isotopic ages (e.g. Steiger et al. 1979; Kalsbeek et al. 1993, 1999). Isotopic mineral ages are generally Cale- donian, testifying to widespread medium- to high- grade Caledonian metamorphism (e.g. Dallmeyer & Strachan 1994; Dallmeyer et al. 1994; Brueckner et al. 1998). Proterozoic sedimentary successions overlying the crystalline gneiss complexes are widespread in the southern half of the Caledonides. An older late Meso- proterozoic to early Neoproterozoic succession (Krum- medal supracrustal sequence and equivalents; Higgins 1988) preserves isotopic evidence of a pre-Caledonian (~ 930 Ma) thermal event, and in many areas hosts ~ 930 Ma augen granite intrusions (Jepsen & Kalsbeek 1998; Kalsbeek et al. 2000; Watt et al. 2000; Leslie & Nutman 2000, 2003). The younger, Neoproterozoic, Eleonore Bay Supergroup is conspicuous in the fjord region of East Greenland (72°–74°30′N), where it is unconformably overlain by the Vendian Tillite Group and Lower Palaeozoic sediments, forming a succes- sion up to 18.5 km thick. Both sedimentary succes- sions are variably affected by Caledonian metamor- phism and deformation, and both host Caledonian granites (Kalsbeek et al. 2001a, b). In the northern part of the East Greenland Caledo- nides, latest Palaeoproterozoic to Mesoproterozoic supracrustal successions are represented by the Inde- pendence Fjord Group and associated volcanic rocks (Figs 1, 2; see also below). These are widely exposed in the Caledonian foreland west of Danmark Fjord, and are also conspicuously developed within the Cale- donian thrust complexes of Kronprins Christian Land, where they are overlain by the Neoproterozoic Rivie- radal Group siliciclastic succession and Hagen Fjord Group (Fig. 2; see also stratigraphy section below). Early work in southern Kronprins Christian Land by Fränkl (1954, 1955) established many of the princi- pal structural features of this part of the East Green- land Caledonides. While subsequent interpretations of the frontal thrust systems were explained by Hurst & McKerrow (1981a, b, 1985) in terms of three nappes, later systematic Survey work has considerably simpli- fied this view. The Vandredalen thrust sheet is now recognised as the westernmost major allochthonous tectonic unit along the entire > 200 km long thrust front in Kronprins Christian Land (Fig. 2; Rasmussen & Smith 1996). The Vandredalen thrust displaces the Neoprot- erozoic rift succession now known as the Rivieradal Group (Smith et al. 2004a, this volume) across the parau- tochthonous foreland succession (Higgins et al. 2001b). The thin-skinned thrust belt west of, and structur- ally underlying, the Vandredalen thrust sheet is de- veloped in an Ordovician to Lower Silurian succes- sion, that continues westwards into the undisturbed foreland sequences west of Danmark Fjord. The suc- cession in this 30–50 km wide, parautochthonous thrust belt is disrupted by a series of east-dipping and SSW–NNE-trending thrusts and associated belts of fold- ing (Fig. 2). A thin-skinned deformation style was also suggested in the earliest studies by Fränkl (1954, 1955), and Peel (1980) distinguished numerous significant thrusts in an W–E traverse through the belt in Kron- prins Christian Land west of Romer Sø. Observations by Peel indicated that the westernmost thrusts extend almost to Danmark Fjord. Regional mapping of the southern part of Kronprins Christian Land, including the parautochthonous thrust belt, was carried out during the 1993–1995 expeditions by the former Geo- logical Survey of Greenland (GGU; Henriksen 1994a, b, 1995, 1996; Higgins 1995). The Vandredalen thrust climbs a steep ramp along the Hekla Sund – Spærregletscher lineament, that is well exposed at the bay Marmorvigen (M on Fig. 2), is almost continuously exposed along the west side of Hekla Sund and extends northwards to the east side of Brede Spærregletscher (BS on Fig. 2). West of the ramp, the thrust follows a long flat in the Ordovi- cian Wandel Valley Formation, that is continuously exposed along the west side of Sæfaxi Elv, the river draining into Marmorvigen. The > 200 km long Van- dredalen thrust sheet front has a general SSW–NNE trend, and is traceable from west of Blåsø through the east end of Centrumsø to west of Romer Sø (Fig. 2). This trend line coincides with another ramp that cuts up through the Ordovician–Silurian platform limestones and dolomites and carries the Vandredalen thrust sheet up to overlie Silurian turbidites of the Lauge Koch Land Formation at present-day exposure levels. The root zone of the Vandredalen thrust sheet, along the SSW–NNE-trending Hekla Sund – Spærregletscher line- ament, coincides approximately with the west margin of the original rift basin (Hekla Sund Basin) in which the Rivieradal Group succession accumulated (Higgins et al. 2001b). GEUS Bulletin 6.pmd 10-02-2005, 09:5443 44 Wandel Sea Basin sequence (post-Caledonian) Samuelsen Høj Formation Lauge Koch Land Formation Odins Fjord Formation Turesø Formation Wandel Valley Formation Kap Holbæk Formation Crystalline basement Thrust Fault Børglum River and Sjælland Fjelde Formations Fyns Sø, Kap Bernhard, Campanuladal Fms Hagen Fjord Gp Rivieradal Group Independence Fjord Gp and basaltic formations Vandredalen thrust Hagen Fjord Group    Vandredalen thrust sheet    ▲ ▲ ▲ ▲ Ro m er Sø D an m ar k Fj or d Amdrup Land Holm Land Hovgaard Ø Kap Bernhoft Dijmphna Sund Cen tru ms ø S K A L L IN G E N Syd vej da l Rivieradal 20°W 81°N Blåsø Nio gha lvfje rdsf jord en Sæ faxi Elv H ek la Su nd Ingolf Fjo rdBS H FL M Va nd re da le n ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ 80°N SP T SP T ▲ ▲ C A LE D O N ID ES Greenland 25 km GEUS Bulletin 6.pmd 10-02-2005, 09:5444 45 East of the Hekla Sund – Spærregletscher lineament a broad zone of latest Palaeoproterozoic to Mesopro- terozoic clastic and volcanic rocks crops out, and still farther east crystalline basement rocks extend to the eastern coast of Kronprins Christian Land (Fig. 2). These broad regions are bounded by steeply inclined shear zones, some of which probably represent major thrusts. The crystalline basement rocks underlying the post-Caledonian Wandel Sea Basin succession in the coastal zone incorporate eclogitic enclaves that testify to deep burial during the Caledonian orogeny, fol- lowed by rapid exhumation (e.g. Gilotti & Ravna 2002; Gilotti et al. 2003). The pronounced SSW–NNE lineament that can be traced from Hovgaard Ø through western Holm Land to Amdrup Land, is generally not well exposed, but appears to have a complex history. This feature is of- ten viewed as a northward continuation, or a splay, of the major, sinistral, Storstrømmen shear zone, de- scribed from Hertugen af Orléans Land (78°N) by Stra- chan & Tribe (1994). The latest movements on the lineament in Kronprins Christian Land are post-Cal- edonian, with eastward downthrow of the Wandel Sea Basin succession. However, in southern Hovgaard Ø and Lambert Land Jones & Escher (1995) record a se- ries of late Caledonian ductile shear zones along the lineament, that preserve evidence of both sinistral and east-side-up displacement. In Lambert Land these shear zones post-date foreland-propagating thrust-stacking events, that place thrust sheets of high-grade crystal- line gneisses (with eclogitic enclaves) above thrust sheets comprising Independence Fjord Group sand- stones. It is considered likely that the high grade base- ment gneisses of Hovgaard Ø and Holm Land form part of major, thick-skinned thrust sheets that once projected westwards, structurally above the strongly sheared and folded Independence Fjord Group west of the Hovgaard Ø – Amdrup Land lineament (see also Fig. 5). Stratigraphy The autochthonous and parautochthonous foreland comprises thick latest Palaeoproterozoic to Mesopro- terozoic successions (Hekla Sund Formation, Aage Ber- thelsen Gletscher Formation, Independence Fjord Group, Zig-Zag Dal Basalt Formation) and associated mafic intrusions (Midsommersø Dolerite Formation); see also Sønderholm & Jepsen (1991). These are over- lain by Neoproterozoic shelf sediments (Hagen Fjord Group: comprising the Jyske Ås, Campanuladal, Kap Bernhard and Fyns Sø Formations). There is a hiatus between the Fyns Sø Formation dolostones and the overlying sandstones of the Kap Holbæk Formation with local developments of palaeokarst (Smith et al. 1999). Another hiatus occurs between the Kap Hol- bæk Formation (early Cambrian) and the overlying Ordovician–Silurian carbonate and siliciclastic rocks. The Neoproterozoic Rivieradal Group is represented only in the allochthonous Vandredalen thrust sheet, and its deposition can be linked to an episode of extensional rifting (Higgins et al. 2001b). All these units were involved to some extent in the Caledonian folding and thrusting, but in the thin-skinned parau- tochthonous belt the thrusts are essentially confined to the Ordovician–Silurian sequence. The best exposed sections through the thin-skinned thrust belt follow the sides of Centrumsø and the val- leys which branch off the west end of this lake. This is the only area where there is sufficient relief and ground control to permit reconstruction of a restorable section (see below). Other good partial sections oc- cur in valleys to the north and south. The extensive plateau areas between valleys are often poorly ex- posed, and here mapping was carried out by spot checks of the sporadic exposures, supplemented by sampling and conodont studies (Rasmussen & Smith 2002). The main formations represented on the maps and cross-sections are listed in Fig. 3, and are briefly described below. Hekla Sund Formation, Aage Berthelsen Gletscher Formation, Independence Fjord Group, Midsommersø Dolerite Formation, Zig-Zag Dal Basalt Formation With the exception of the tholeiitic basalts of the Hekla Sund Formation and Aage Berthelsen Gletscher For- mation, the type areas of these Proterozoic divisions were established on the Caledonian foreland west of Facing page: Fig. 2. Geological map of southern and central Kronprins Christian Land. The frame outline centred on Centrumsø indicates the position of the cross-section and geological map presented in Fig. 4; the extension of the section line beyond the frame is that of the cross-section in Fig. 5. The lineament traceable from Hovgaard Ø through western Holm Land to Amdrup Land, marked by a dashed line, has a complex history (see text). BS, Brede Spærregletscher; FL, Finderup Land; H, Hjørnegletscher; M, Marmorvigen; SPT, Spærreglet- scher thrust. Modified from Higgins et al. (2001a). GEUS Bulletin 6.pmd 10-02-2005, 09:5445 46 Danmark Fjord (Sønderholm & Jepsen 1991). The In- dependence Fjord Group comprises a more than 2 km thick succession of mainly clastic alluvial depo- sits, dominantly white-weathering quartzitic sand- stones (Collinson 1980, 1983). The Midsommersø Dolerite Formation consists of the widespread doleritic sheets, sills and dykes which invade the Independ- ence Fjord Group sandstones (Jepsen 1971; Kalsbeek & Jepsen 1983). The Zig-Zag Dal Basalt Formation comprises at least 1350 m of lava flows which overlie the Independence Fjord Group (Jepsen et al. 1980; Kalsbeek & Jepsen 1984); they are considered to be the extrusive equivalents of the Midsommersø Dolerite Formation. Highly deformed quartzitic sandstones, doleritic dykes and basaltic lava sequences which crop out in the alpine region of eastern Kronprins Christian Land within the Caledonian orogenic belt have traditionally been regarded as equivalents of the foreland divisions. However, the Survey’s regional mapping revealed that the basaltic sequences found in the thrust complexes of Kronprins Christian Land do not overlie the Inde- pendence Fjord Group, but are interbedded with the lower levels of the quartzite succession. These basal- Fig. 3. Summary stratigraphic scheme of Proterozoic and Palaeozoic units depicted on the maps, and their relationships to Iapetus opening (modified from Smith et al. 1999). Non-deposition or erosion is depicted by vertical ruling. Silurian Ordovician Cambrian Vendian Sturtian Riphean Lauge Koch Land Formation Samuelsen Høj Formation Odins Fjord Formation Turesø Formation Børglum River Formation Sjælland Fjelde Formation Wandel Valley Formation Kap Holbæk Formation Hagen Fjord Group Fyns Sø Fm Kap Bernhard Fm Campanuladal Fm Jyske Ås Fm Zig-Zag Dal Basalt Formation Independence Fjord Group Hekla Sund Fm, Aage Berthelsen Gletscher Fm, & interbedded quartzites thermal subsidence extensional rifting and block tilting extensional riftingRivieradal Group (allochthonous Vandredalen thrust sheet only) post-rift thermal subsidence Baltica collision thrust loaded flysch basin TECTONIC SETTING DEPOSITIONAL ENVIRONMENT STRATIGRAPHY lapetus passive margin lapetus opening pre-lapetus rift-sag cycle intracratonic extensional events thermal subsidence block tilting ZZ IF HS/AB KH RG    GEUS Bulletin 6.pmd 10-02-2005, 09:5446 47 tic sequences are distinguished as the Hekla Sund Formation and Aage Berthelsen Gletscher Formation (Pedersen et al. 2002). SHRIMP isotopic studies on rhyolites of the Hekla Sund Formation yielded an age of 1740 Ma (Kalsbeek et al. 1999). This result implies that either the age range of the Independence Fjord Group must be extended downwards to the later part of the Palaeoproterozoic, or there are two superficial- ly indistinguishable quartzite sequences, of which the older unnamed succession is interbedded with the Hekla Sund and Aage Berthelsen Gletscher Forma- tions. The first alternative is adopted here. Quartzite- dyke-basalt associations similar to the foreland suc- cession are presumed to underlie the entire parauto- chthonous region. Rivieradal Group The succession of sandstones, mudstones, conglome- rates and some carbonate rocks first mapped by Fränkl (1954, 1955), and assigned by Hurst & McKerrow (1981a, b) to a single sequence that they referred to as the ‘Rivieradal sandstones’, has been formally de- fined as the Rivieradal Group (Smith et al. 2004a, this volume). The Rivieradal Group is restricted to the Van- dredalen thrust sheet, where it is overlain conform- ably by units of the Hagen Fjord Group. Fränkl had recognised that the Neoproterozoic Rivieradal Group was not represented on the foreland, and introduced the term ‘Hekla Sund Basin’ for its area of deposition. Field work by GGU in 1993–1995 demonstrated that the Rivieradal Group is 7.5–10 km thick. It was also shown that the sediments of the Rivieradal Group had accumulated in an east-facing, half-graben rift-basin, bounded to the west by extensional faults; this basin was estimated to have been at least 200 km long and 50 km wide (Higgins et al. 2001b). During the Cale- donian orogeny the Rivieradal Group was displaced westwards across the western margin of the rift basin as the Vandredalen thrust sheet. The root zone of this thrust sheet and the remnants of the original rift basin can be traced in a narrow belt through the centre of the alpine region along the Hekla Sund – Spærreglet- scher lineament (Fig. 2). Hagen Fjord Group (and Kap Holbæk Formation) Representatives of the Hagen Fjord Group are preser- ved in the frontal portions of the Vandredalen thrust sheet, resting conformably on the Rivieradal Group. In the foot wall of the Vandredalen thrust, as else- where in eastern North Greenland, the Hagen Fjord Group rests directly on Independence Fjord Group lithologies, locally with an intervening basal clastic unit. The Hagen Fjord Group is thus viewed as a trans- gressive, post-rift sequence, and its presence in both the hanging wall and foot wall of the Vandredalen thrust enables the displacement on the Vandredalen thrust to be estimated at 35–50 km (Higgins et al. 2001b). The Jyske Ås Formation (Fig. 3) at the base of the group occurs only west of Danmark Fjord in the foreland, and is not considered further here. In the parautochthonous region with which this paper is concerned, four formations are recognised in addi- tion to the basal clastic unit, although the uppermost unit (the Kap Holbæk Formation) is now formally excluded from the Hagen Fjord Group (see below). 1. Basal clastic unit. This dominantly conglomeratic unit directly overlies Independence Fjord Group quartzitic sandstones, and is overlain by siltstones and mudstones ascribed to the Campanuladal For- mation. The unit was first recorded at Hjørneglet- scher (H on Fig. 2) on the north side of inner Ingolf Fjord (Jepsen & Kalsbeek 1981) where it is a few metres thick. In 1993 two additional developments of the unit, respectively 35 m and 0–60 m thick, were located along the margin of the alpine region north of Sæfaxi Elv (Jepsen et al. 1994). 2. Campanuladal Formation. Dominated by green and red fine-grained sandstones, siltstones and mudstones, it is about 110–175 m thick in the fore- land areas west of the head of Danmark Fjord (Clem- mensen & Jepsen 1992). In the parautochthonous region between inner Ingolf Fjord and Sæfaxi Elv, Jepsen & Kalsbeek (1985) reported 0–80 m of mudstone and sandstone of the formation overly- ing either the basal conglomeratic unit or the Inde- pendence Fjord Group. 3. Kap Bernhard Formation. This comprises reddish- brown limestones with minor amounts of silt, and is about 150 m thick at the head of Danmark Fjord (Clemmensen & Jepsen 1992). The formation is up GEUS Bulletin 6.pmd 10-02-2005, 09:5447 48 to 400 m thick in the frontal region of the Vandre- dalen thrust sheet. 4. Fyns Sø Formation. At its type locality at the head of Danmark Fjord (Craig & Jepsen 1995), it is made up of 356 m of spectacular, cliff-forming, yellow- weathering dolostones, characteristically preserving well-formed stromatolites. A similar thickness (~ 400 m) is seen in both the foot wall and the hanging wall of the Vandredalen thrust. 5. Kap Holbæk Formation. This was originally the upper formation of the Hagen Fjord Group (Clem- mensen & Jepsen 1992). Recognition that the for- mation is early Cambrian, and that the hiatus be- tween it and the underlying Fyns Sø Formation cov- ers the entire Vendian (Fig. 3), led Smith et al. (2004b, this volume) to formally exclude it from the Hagen Fjord Group. The formation was recognised in the parautochthonous belt in the inner parts of Ingolf Fjord in 1994 (Jepsen & Sønderholm 1994), and here is up to 180 m thick; it comprises variegated mud- stones at the base overlain by a light and dark col- oured sandstone succession. Sandstone-filled fis- sures and cave-like lenses in the upper surface of the underlying Fyns Sø Formation, first recorded by Fränkl (1954, 1955), have been interpreted as palaeokarst (Smith et al. 1999). The Kap Holbæk Formation was recognised in the hanging wall of the Vandredalen thrust by Hurst & McKerrow (1981a, b), who placed it in their ‘Finderup Land nappe’. Lower Palaeozoic platform The Lower Palaeozoic platform strata of eastern North Greenland are the easternmost representatives of the Franklinian Basin succession, which is exposed in a broad, 900 km long belt across North Greenland (Higgins et al. 1991). The earliest Lower Palaeozoic platform strata in the parautochthonous belt of east- ern Kronprins Christian Land are the Early Ordovician limestones and dolostones of the Wandel Valley For- mation (Rasmussen & Smith 1996; Smith et al. 2004b, this volume), which rest unconformably on the Fyns Sø Formation or Kap Holbæk Formation. Uplift of east- ern North Greenland and subsequent erosion have resulted in a progressive overstep of the Early Ordo- vician from west to east across North Greenland (Peel & Smith 1988). There is also a north–south compo- nent to the overstep, since south of Kronprins Chri- stian Land, in Lambert Land, the Hagen Fjord Group is missing and the Wandel Valley Formation rests di- rectly on Independence Fjord Group lithologies (Smith et al. 1999; Smith 2000). A fuller stratigraphical de- scription of the Lower Palaeozoic platform limestone and dolostone succession is given by Smith et al. (2004b, this volume). The following formations are distin- guished on the maps and cross-sections of this paper. 1. Wandel Valley Formation (Upper Ibexian – Middle Whiterockian). Three limestone and dolostone members are present in the parautochthonous belt, all very similar in their development to their coun- terparts on the foreland around Danmark Fjord, and with a total thickness of about 335 m. 2. Sjælland Fjelde Formation (Upper Whiterockian). About 100 m thick, it is divided into a lower dark grey burrow-mottled limestone and dolostone unit and an upper grey dolostone unit. The Vandredalen thrust follows a long flat in the middle part of the formation, well seen along the west side of Sæfaxi Elv, before climbing a ramp to another flat in the upper dolomite unit. Near the head of Ingolf Fjord, about 70 km to the north, the Vandredalen thrust occupies the same stratigraphic level. 3. Børglum River Formation (Mohawkian – Upper Cincinatian). The formation is widespread in the parautochthonous belt, where it comprises a thick succession of dominantly dark, nodular, burrow- mottled limestones with abundant fossils. A com- plete section through the unit is not seen in the parautochthonous belt, but is probably close to the thickness of 430 m measured in the autochthonous foreland areas further to the north-west (Smith et al. 1989). Facing page: Fig. 4. Geological map and restored cross-section of the thin- skinned thrust belt in the Centrumsø region. A: Geological map and location of section line; see also frame in Fig. 2. Base camp indicated by filled triangle. B: Cross-section with calculated displacements on individual thrusts in kilometres (e.g. 2.75) based on a line and area balance; only the Sjælland Fjelde Formation is given a distinctive ornament, with other formations indicated by two-letter abbreviations (see legend on map of Fig. 4A). Note the gently eastwards- dipping floor thrust at the base of the Wandel Valley Forma- tion. C: Model section with thrusts restored; note reproduced at a smaller scale than the cross-section in B. In both B and C the thrusts are indicated by thicker lines. GEUS Bulletin 6.pmd 10-02-2005, 09:5448 4 9 ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ Ce nt ru m sø Section line 0 5 km 0 5 km 0 5 km N Lauge Koch Land Odins Fjord Turesø Sjælland Fjelde Fyns Sø Kap Bernhard Rivieradal Group Thrust LK OF TU BR SF FS WV WV KB RG Wandel Valley Børglum River ▲ ▲ Base camp A B C LK OF OF TU BR WV LK TU TU BR BR BR BR BR WV WV BR WV LK OF TU LK LK OF LK LK OF OFTU TUBR BR FS KB RG WV BR OF TU TU WV 0.05 0.55 0.4 0.9 0.95 0.751.8 1.0 2.85 5.4 km 1.0 km 2.75 2.75 4.9 0.8 9.15 km 8.45 km 22.4 km G E U S B u lle tin 6 .p m d 1 0 -0 2 -2 0 0 5 , 0 9 :5 4 4 9 50 4. Turesø Formation (Upper Cincinnatian – Lower Llandovery). The formation spans the Ordovician– Silurian boundary (Armstrong 1990), and where measured 7 km west of Centrumsø comprises about 200 m of variably coloured dolostones and lime- stones (see Fig. 6A). The colour variations make the formation conspicuous and easily recognisable. Towards the eastern end of Centrumsø, just west of the Vandredalen thrust sheet front, the forma- tion thickens to at least 350 m; here trains of tight folds are developed in the dolostone-dominated in- tervals (see Fig. 6B). 5. Odins Fjord Formation (mid-Llandovery). The for- mation is widely exposed in southern Kronprins Christian Land close to the Vandredalen thrust sheet front, where it is at least 220 m thick, although de- formation and poor exposure make this estimate uncertain. Christie & Peel (1977) estimated a thick- ness of 320 m in south-east Peary Land. The transi- tion from the underlying Turesø Formation is marked by a change in colour from pale grey to pale brown, and in lithology from dolostone to lime- stone rich in tabulate corals and stromatoporoids. 6. Samuelsen Høj Formation (Upper Llandovery). Developed as conspicuous reefs, the formation is represented by several major bodies in northern Kronprins Christian Land; those in southern areas are generally smaller and mainly occur in a belt just west of the Vandredalen thrust sheet front (Fig. 2). Only one small body is known south of Centrum- sø, and there are none in the line of section (Fig. 4). 7. Lauge Koch Land Formation (uppermost Llandovery – Wenlock). The Silurian flysch of Kronprins Chris- tian Land was assigned by Hurst & Surlyk (1982) to Fränkl’s ‘Profilfjeldet Shales’, which was given mem- ber rank within the Lauge Koch Land Formation. The sequence is widely involved in the major thrusts of northern Kronprins Christian Land, where a maxi- mum thickness of 400 m was estimated (Hurst & Surlyk 1982). Further south the formation crops out mainly in a zone just west of the Vandredalen thrust sheet front. Only two thrust-bounded inliers occur south of Centrumsø; here the lower 50 m of the formation is characterised by black shaly siltstones interbedded with dark grey to black bituminous and nodular carbonate rocks (Smith et al. 2004b, this volume). Structure The most important thrusts within the 30–50 km wide thin-skinned thrust belt of Kronprins Christian Land are depicted in Figs 2 and 4. They make up a major imbricate stack beneath a former extension of the Vandredalen thrust sheet. Individual thrusts dip east- wards at angles varying from about 30° to 70°, although the steeper thrusts appear to represent over-steepen- ing arising from further thrust displacement in the foot wall succession. Many thrusts can be followed for several tens of kilometres, some for as much as 75 km along strike. Major folding accompanied the thrust- ing, although this is normally conspicuous only in certain formations. About 25 km south of Centrumsø several major thrusts die out. Further south, only one major thrust has been traced for 30 km west of the Vandredalen thrust front, and this divides into two thrusts west of Blåsø (Fig. 2). All the Ordovician–Silurian stratigraphic units from the Wandel Valley Formation to the Lauge Koch Land Formation are involved in the thrusting. Individual thrust movements range from a few hundred metres to several kilometres. Despite topographic relief of 1000 m, matching foot wall and hanging wall cut-offs are rarely observed. Estimates of thrust displacements therefore rely on the construction of a restorable cross- section. The best exposed sections are, in the north, the valley system west of Romer Sø (described by Peel 1980) and, in the south, the valley system containing Centrumsø with which this paper is mainly concerned. A restorable cross-section through the Centrumsø area constructed perpendicular to the thrust trends is pre- sented in Fig. 4. Prior to attempting to restore the cross-section, a series of cross-sections (not reproduced here) were constructed along profile lines north and south of Centrumsø to gain an impression of the possible range of displacements. The section line of Fig. 2 was cho- sen because of the excellent exposures on the cliff walls north and south of the lake, and because of the generally good ground control. Initial section construc- tion was at a scale of 1:50 000, on the basis of enlarged copies of the Survey’s 1:100 000 topographic maps. Thrust trajectories and fold shapes were projected into the line of section using the best available thickness estimates for formations as noted above. The maxi- mum observed thickness estimate of 400 m for the Lauge Koch Land Formation was used. In respect of the Turesø Formation, the 200 m thickness was used in the west, and 350 m in the eastern part of the section. GEUS Bulletin 6.pmd 10-02-2005, 09:5450 51 Balancing was attempted initially assuming that a single floor thrust in the parautochthonous belt fol- lowed the base of the Børglum River Formation (as the Wandel Valley and Sjælland Fjelde Formations were not visibly involved in the thrusting along the line of profile). However, all attempts at a balance with this constraint produced an unrealistic undulating floor thrust (not illustrated here). The floor thrust was then reassigned downwards to the base of the Wandel Val- ley Formation with, in addition, a major thrust at the base of the Børglum River Formation. This change is justified on the grounds that: (1) The Wandel Valley and Sjælland Fjelde Formations are both involved in the thrusting in northern Kronprins Christian Land (see fig. 1 in Peel 1980); (2) Along Sæfaxi Elv, immediately north of the eastward extension of the Centrumsø cross-section, several highly disturbed bedding-paral- lel shear zones were observed near the base of the Wandel Valley Formation. The restoration of the Cen- trumsø cross-section achieved on this basis (Fig. 4B), exhibits a very gentle eastward inclination for the floor thrust at the base of the Wandel Valley Formation. In this model all the thrusts west of the end of Centrum- sø root into the floor thrust, whereas the thrusts ex- posed along the margins of Centrumsø all root into the slightly higher flat thrust following the base of the Børglum River Formation. The section restoration presented in Fig. 4 involved resolution of several problems. At the west end of the section there is a very broad mapped expanse of Børg- lum River Formation between two observed major thrusts (see map Fig. 4A). The 4.5 km long valley sec- tion shows the sequence dipping at moderate angles eastwards, with locally some dislocation and associ- ated folding. However, since the maximum thickness of the Børglum River Formation is probably about 430 m, restoration could only be achieved assuming the formation to be repeated in a duplex with displace- ments of 400–1800 m on the individual thrusts. The positions of the duplex thrusts were not identified during the field work, mainly because the significance of the over-thickened section was not appreciated; thus, while depicted on the cross-sections (Fig. 4B, C), these thrusts are not shown on the map (Fig. 4A). A further problem concerned a long central seg- ment of the cross-section which exhibits a syncline at the west end (see Fig. 6A) and a broad flat anticline in the centre with the lowest levels of the Børglum River Formation exposed at valley level. This could only be satisfactorily accommodated by introducing a ramp duplicating the Wandel Valley and Sjælland Fjelde Formations over a distance of 5.4 km (central part of section in Fig. 4B). In the cliff north of the base camp at the west end of Centrumsø, a long flat thrust brings the Børglum River Formation above a thin sequence of the Turesø Formation. South of Centrumsø the same thrust changes levels and takes the Turesø Formation above the Odins Fjord Formation on an equally long flat thrust. Similar long thrust flats are interpreted to exist at the eastern end of the section, with the largest dis- placement on an individual thrust estimated at 4.9 km. Intense folding at the eastern end of the section, just west of the Vandredalen thrust sheet front (see Fig. 6B), and the implications of such internal distortion in other parts of the section, cannot be accurately depicted. Total displacement on the basis of the model resto- ration in Fig. 4B is estimated at 17.6 km. The thrusts depicted in the east part of the section along Cen- trumsø have a total displacement of 8.45 km rooting into the thrust at the base of the Børglum River For- mation, which merges with the Vandredalen thrust at the Vandredalen thrust front. The thrusts west of Cen- trumsø root into a floor thrust following the base of the Wandel Valley Formation and have an estimated total of 9.15 km displacement; this thrust merges with the Vandredalen thrust east of the line of section in the vicinity of Marmorvigen (Fig. 2). The restoration implies that an original 43 km wide segment of the parautochthonous belt has been reduced to about 25.4 km in the line of section, a shortening of approxi- mately 45%. The restored section depicted in Fig. 4B demon- strates that the model chosen is realistic. It invokes only two major flat thrusts, both of which merge east- wards with the Vandredalen thrust. Conodont geothermometry Epstein et al. (1977) demonstrated that colour varia- tions of conodont elements are principally related to temperature. They erected a scale of conodont altera- tion indices (CAI 1–5) ranging from pale yellow through shades of brown to black, corresponding to a temperature range from < 50°–300°C. Higher altera- tion indices (CAI 6–8), in which the conodont ele- ments progressed from black through grey to white, were calibrated by Rejebian et al. (1987) as correspond- ing to a temperature range from 300°C to over 600°C. A regional description of conodont geothermometry GEUS Bulletin 6.pmd 10-02-2005, 09:5451 52 in the Kronprins Christian Land area has been pre- sented by Rasmussen & Smith (2001). Conodonts studied in Kronprins Christian Land were recovered from stratigraphic units ranging in age from mid-Early Ordovician (Wandel Valley Formation) to Llandovery (Lauge Koch Land Formation). Lithologies varied from unaltered platform dolostones and lime- stones to their highly sheared equivalents underlying the Vandredalen thrust sheet. Whereas the degree of internal shearing and deformation had a significant effect on the morphological character of the conodont elements, it had no apparent effect on the colour al- teration indices. The CAI isothermal zones run paral- lel to the thrust trends and the Vandredalen thrust sheet front in southern Kronprins Christian Land. CAI values of 2–3 were seen west of Danmark Fjord. A broad zone of CAI 3 extends eastwards to approxi- mately the west limit of the cross-section in Fig. 4. Most of the cross-section is within the zone of CAI 4, rising to CAI 5 at the eastern end adjacent to the front of the Vandredalen thrust sheet. The limestones and dolostones beneath the Vandredalen thrust sheet, ex- posed along Sæfaxi Elv, are in CAI zone 5 increasing to CAI 5–6 in the easternmost exposures at Marmorvi- gen. The CAI temperatures indicate the maximum thick- ness of the Caledonian overburden, comprising the Vandredalen thrust sheet and possible higher thrust units. The thickness was determined from estimates of geothermal gradients and the thermal conductivity of the rock units involved (see Rasmussen & Smith 2001, for details). The results imply that the approxi- mate thickness of the maximum overburden in the area of the cross-section (Fig. 5), ranged from about 6 km at the west end of the cross-section to 10.7 km farther east at the front of the Vandredalen thrust sheet (Fig. 6C). The highest CAI values at Marmorvigen point to an overburden of 12.5 km (Rasmussen & Smith 2001). The assumed extent and thickness of the Vandre- dalen thrust sheet formerly present above the parau- tochthonous zone are also indicated in Fig. 5. The Hagen Fjord Group in the hanging wall exhibits a cut-off against the Vandredalen thrust along much of the Vandredalen thrust sheet front on the west side of Vandredalen. Thus, the former extent of the Vandre- dalen thrust sheet across the parautochthonous zone must have consisted essentially of a packet of Ordo- vician–Silurian carbonate and siliciclastic rocks. The thickness of this packet was probably not much greater than 2 km (Fig. 5). The only uncertainty in this esti- mation of the thickness concerns the contribution of turbidites of the Lauge Koch Land Formation. A maxi- mum thickness of 400 m has been assumed for this unit in the cross-section, being the maximum thick- ness preserved in present-day exposures (Hurst & Surlyk 1982). The Silurian turbidites of North Green- land were derived from erosion of the rising Caledo- nian mountain chain. The thickness of the turbidite succession that may have accumulated in the western part of present Kronprins Christian Land before it was over-ridden by the westward-propagating Caledonian thrust sheets is unknown. Between 3 and 10 km of additional overburden above the Vandredalen thrust 0 km 5 0 22 km 6 km 12.5 km 50 km ? 100 km ? Or d.– Sil ST 18 km WSW ESE VT SPT 50 km E S T I M AT E D OV E R B U R D E N F R O M C O N O D O N T A LT E R AT I O N ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ ▲ Crystalline basement Rivieradal Group Hagen Fjord Group Ordovician – Silurian Independence Fjord Group and associated volcanics Fig. 5. Simplified cross-section through the Caledonian fold belt in Kronprins Christian Land, from Higgins et al. (2001b); for section line see Fig. 2. The maximum overburden deduced from conodont alteration indices (indicative of eastward increase in tempera- ture) is also shown. SPT, Spærregletscher thrust; ST, Caledonian sole thrust; VT, Vandredalen thrust. GEUS Bulletin 6.pmd 10-02-2005, 09:5452 53 OF OF TU TU RG VT A B C Fig. 6. A: Syncline in line of cross-section looking north, 7 km west of the Centrumsø base camp. OF, Odins Fjord Forma- tion; TU, Turesø Formation. Cono-donts have CAI values of 4, indicative of a former over- burden of about 6.8 km. Summit at centre is 500 m above the valley floor. Photo: J. Lautrup. B: Intense folding in variegated dolomites of the Turesø Forma- tion (TU). North side of Cen- trumsø, about 3 km west of the Vandredalen thrust front. Cono- donts have CAI values of 4–5, indicative of an overburden of about 8–9 km. Plateau is about 750 m above the lake level (foreground). Photo: J. Lautrup. C: Outlier of Rivieradal Group (RG) conglomerates and sandstones in the Vandredalen thrust sheet, overlying Ordovi- cian carbonates of the Odins Fjord Formation (OF) on the west side of Vandredalen. The Vandredalen thrust (VT) follows the marked discordance. Cono- donts from the carbonates of the Odins Fjord Formation have CAI values of 5, indicative of a former overburden of about 10.7 km. Summit is 850 m above the valley floor in the foreground. GEUS Bulletin 6.pmd 10-02-2005, 09:5453 54 sheet would be required to reach the temperatures demonstrated by the conodont alteration pattern, and it is considered unlikely that this can be accounted for by substantially increasing only the contribution of the Lauge Koch Land Formation turbidites. It is more probable that higher, westward-propagating thrust sheets were formerly present above the Vandredalen thrust sheet. These are likely to have comprised units such as the Independence Fjord Group quartzitic sand- stones with associated dolerite dykes and sills, and the Hekla Sund Formation basalts (representatives of which crop out in the mountainous region east of the Hekla Sund – Spærregletscher lineament). These units would have been transported westwards on the Spær- regletscher thrust (SPT in Figs 2, 5). Lower Palaeozoic formations may also have been present in the proxi- mal parts of this thrust sheet. All the CAI zones are based on sample collections from the parautochthonous zone structurally under- lying the Vandredalen thrust sheet. This zone is part of a thin-skinned thrust belt, and therefore the most likely setting to account for the increased tempera- tures would be burial of the parautochthonous zone beneath a pile of westward-directed Caledonian thrust sheets. Allowing for subsidence of the parautoch- thonous zone that resulted from the weight of the overlying thrust burden, the thrust sheets must still have made up a substantial mountain chain, increas- ing in altitude eastwards where summits may have attained altitudes of about 3–4 km. Conclusions The rock units which constitute the up to 50 km wide thin-skinned thrust belt west of the Vandredalen thrust front extend westwards into undisturbed foreland. The thrust belt is therefore viewed as parautochthonous. The deformation associated with the eastward-dipping thrusts of the parautochthonous zone involves only Ordovician–Silurian rock units and is essentially thin- skinned in style. A line-and-area restoration along the best exposed section through the thrust belt, i.e. along Centrumsø and adjacent valleys, can be achieved assuming that the observed thrusts root into two flat thrusts. One is depicted as the Caledonian floor or sole thrust, in this region located at the base of the Wandel Valley For- mation; the second slightly higher thrust is assumed to lie at the base of the Børglum River Formation. Both thrusts are assumed to merge eastwards with the Van- dredalen thrust. Total displacement of 17.6 km on the two flat thrusts in the model restoration implies that an original 43 km wide segment of the parautoch- thonous belt has been reduced to 25.4 km, a shorten- ing of 45% in the line of section. The colour changes experienced by conodont ele- ments reflect variations in temperature which can be linked to the maximum thickness of overburden dur- ing the Caledonian orogeny. Overburden estimates increase systematically from 6 km at the west end of the cross-section to 10.7 km at the Vandredalen thrust front, and farther east to 12.5 km at Marmorvigen (Fig. 5). As the Vandredalen thrust sheet overlying the parau- tochthonous zone was probably not much more than 2 km thick, the remainder of the estimated overbur- den must have comprised higher thrust sheets, since eroded, that projected westwards across the parautoch- thonous belt. Acknowledgements The field and conodont studies of J.A.R. were finan- cially supported by the Carlsberg Foundation (Grant no. 950164/20-1292). The helpful comments of the two reviewers, Robin Strachan and Brian Chadwick, are gratefully acknowledged. References Armstrong, H.A. 1990: Conodonts from the Upper Ordovician – Lower Silurian carbonate platform of North Greenland. Bulle- tin Grønlands Geologiske Undersøgelse 159, 151 pp. Brueckner, H.K., Gilotti, J.A. & Nutman, A.P. 1998: Caledonian eclogite-facies metamorphism of Early Proterozoic protoliths from the North-East Greenland eclogite province. Contribu- tions to Mineralogy and Petrology 130, 103–120. Christie, R.L. & Peel, J.S. 1977: Cambrian–Silurian stratigraphy of Børglum Elv, Peary Land, eastern North Greenland. Rapport Grønlands Geologiske Undersøgelse 82, 48 pp. Clemmensen, L.B. & Jepsen, H.F. 1992: Lithostratigraphy and geological setting of Upper Proterozoic shoreline-shelf depo- sits, Hagen Fjord Group, eastern North Greenland. Rapport Grønlands Geologiske Undersøgelse 157, 27 pp. Collinson, J.D. 1980: Stratigraphy of the Independence Fjord Group (Proterozoic) of eastern North Greenland. Rapport Grønlands Geologiske Undersøgelse 99, 7–23. Collinson, J.D. 1983: Sedimentology of unconformities within a fluvio-lacustrine sequence; Middle Proterozoic of eastern North Greenland. Sedimentary Geology 34, 145–166. Craig, L.E. & Jepsen, H.F. 1995: Late Proterozoic Hagen Fjord Group: stratigraphic relationships between the Fyns Sø For- GEUS Bulletin 6.pmd 10-02-2005, 09:5454 55 mation and Kap Holbæk Formation – including a new refer- ence section through the Fyns Sø Formation. In: Higgins, A.K. (ed.): Express report: eastern North Greenland and North- East Greenland 1995, 53–57. Unpublished report, Geological Survey of Greenland, Copenhagen. Dallmeyer, R.D. & Strachan, R.A. 1994: 40Ar/39Ar mineral age con- straints on the timing of deformation and metamorphism, North-East Greenland Caledonides. In: Higgins, A.K. (ed.): Geology of North-East Greenland. Rapport Grønlands Geolo- giske Undersøgelse 162, 153–162. Dallmeyer, R.D., Strachan, R.A. & Henriksen, N. 1994: 40Ar/39Ar mineral age record in NE Greenland: implications for tectonic evolution of the North Atlantic Caledonides. Journal of the Geological Society (London) 151, 615–628. Epstein, A.G., Epstein, J.B. & Harris, L.D. 1977: Conodont color alteration – an index to organic metamorphism. Professional Paper United States Geological Survey 995, 27 pp. Fränkl, E. 1954: Vorläufige Mitteilung über die Geologie von Kron- prins Christians Land (NE-Grönland, zwischen 80°–81°N und 19°–23°W). Meddelelser om Grønland 116(2), 85 pp. Fränkl, E. 1955: Weitere Beiträge zur Geologie von Kronprins Christians Land (NE-Grönland, zwischen 80° und 80°30′N). Meddelelser om Grønland 103(7), 35 pp. Gilotti, J.A. & Ravna, E.J.K. 2002: First evidence for ultrahigh- pressure metamorphism in the North-East Greenland Caledo- nides. Geology 30, 551–554. Gilotti, J.A., Nutman, A.P, Brueckner, H.K. & McClelland, W.C. 2003: Devonian collision along the northeastern margin of Laurentia, Greenland Caledonides. Geological Society of America: Abstracts with Programs 35, n. 3. Henriksen, N. (ed.) 1994a: Express report: eastern North Green- land and North-East Greenland 1994, 126 pp. Unpublished report, Geological Survey of Greenland, Copenhagen. Henriksen, N. 1994b: Eastern North Greenland 1993–1995 – a new 1:500 000 mapping project. Rapport Grønlands Geolo- giske Undersøgelse 160, 47–51. Henriksen, N. 1995: Eastern North Greenland 1994, the 1:500 000 mapping project. Rapport Grønlands Geologiske Undersøgel- se 165, 53–58. Henriksen, N. 1996: Conclusion of the 1:500 000 field mapping in eastern North Greenland. Bulletin Grønlands Geologiske Undersøgelse 172, 42–48. Higgins, A.K. 1988: The Krummedal supracrustal sequence in East Greenland. In: Winchester, J.A. (ed.): Later Proterozoic stratigraphy of the northern Atlantic regions, 86–96. Glasgow & London: Blackie and Son Ltd. Higgins, A.K. (ed.) 1995: Express report: eastern North Green- land and North-East Greenland 1995, 171 pp. Unpublished report, Geological Survey of Greenland, Copenhagen. Higgins, A.K., Ineson, J.R., Peel, J.S., Surlyk, F. & Sønderholm, M. 1991: Lower Palaeozoic Franklinian Basin of North Green- land. In: Peel, J.S. & Sønderholm, M. (eds): Sedimentary ba- sins of North Greenland. Bulletin Grønlands Geologiske Un- dersøgelse 160, 71–139. Higgins, A.K., Leslie, A.G., Smith, M.P. & Rasmussen, J.A. 2001a: Neoproterozoic – Lower Palaeozoic stratigraphical relation- ships in the marginal thin-skinned thrust belt of the East Green- land Caledonides: comparisons with the foreland in Scotland. Geological Magazine 138(2), 143–160. Higgins, A.K., Soper, N.J., Leslie, A.G., Smith, M.P., Rasmussen, J.A. & Sønderholm, M. 2001b: The Neoproterozoic Hekla Sund Basin, eastern North Greenland: a pre-Iapetan extensional sequence thrust across its rift shoulders during the Caledo- nian orogeny. Journal of the Geological Society (London) 158, 487–489. Hurst, J.M. & McKerrow, W.S. 1981a: The Caledonian nappes of eastern North Greenland. Nature, London 290, 772–774. Hurst, J.M. & McKerrow, W.S. 1981b: The Caledonian nappes of Kronprins Christian Land, eastern North Greenland. Rapport Grønlands Geologiske Undersøgelse 106, 15–19. Hurst, J.M. & McKerrow, W.S. 1985: Origin of the Caledonian nappes of North-East Greenland. In: Gee, D.G. & Sturt, B.A. (eds): The Caledonide orogen – Scandinavia and related ar- eas, 1065–1069. Chichester: John Wiley & Sons. Hurst, J.M. & Surlyk, F. 1982: Stratigraphy of the Silurian turbidite sequence of North Greenland. Bulletin Grønlands Geologiske Undersøgelse 145, 121 pp. Jepsen, H.F. 1971: The Precambrian, Eocambrian and Early Pal- aeozoic stratigraphy of the Jørgen Brønlund Fjord area, Peary Land, North Greenland. Meddelelser om Grønland 192(2), 42 pp. Jepsen, H.F. & Kalsbeek, F. 1981: Non-existence of the Carolinidian orogeny in the Prinsesse Caroline-Mathilde Alper of Kron- prins Christian Land, eastern North Greenland. Rapport Grøn- lands Geologiske Undersøgelse 106, 7–14. Jepsen, H.F. & Kalsbeek, F. 1985: Evidence for non-existence of a Carolinidian fold belt in eastern North Greenland. In: Gee, D.G. & Sturt, B.A. (eds): The Caledonide orogen – Scandina- via and related areas, 1071–1076. Chichester: John Wiley & Sons. Jepsen, H.F. & Kalsbeek, F. 1998: Granites in the Caledonian fold belt of East Greenland. In: Higgins, A.K. & Frederiksen, K.S. (eds): Caledonian geology of East Greenland 72°–74°N: pre- liminary reports from the 1997 expedition. Danmarks og Grøn- lands Geologiske Undersøgelse Rapport 1998/28, 73–82. Jepsen, H.F. & Sønderholm, M. 1994: Sedimentological studies of the Hagen Fjord Group and ‘Rivieradal sandstones’ (Late Pro- terozoic), eastern North Greenland. In: Henriksen, N. (ed.): Express report: eastern North Greenland and North-East Green- land 1994, 39–48. Unpublished report, Geological Survey of Greenland, Copenhagen. Jepsen, H.F., Kalsbeek, F. & Suthren, R.J. 1980: The Zig-Zag Dal Basalt Formation, North Greenland. Rapport Grønlands Geo- logiske Undersøgelse 99, 25–32. Jepsen, H.F., Escher, J.C., Friderichsen, J.D. & Higgins, A.K. 1994: The geology of the north-eastern corner of Greenland – photogeological studies and 1993 field work. Rapport Grøn- lands Geologiske Undersøgelse 151, 21–33. Jones, K.A. & Escher, J.C. 1995: An E–W traverse across the Cal- edonian fold belt from Lambert Land to Norske Øer. In: Higgins, A.K. (ed.): Express report: eastern North Greenland and North-East Greenland 1995, 23–41. Unpublished report, Geological Survey of Greenland, Copenhagen. Kalsbeek, F. & Jepsen, H.F. 1983: The Midsommersø Dolerites GEUS Bulletin 6.pmd 10-02-2005, 09:5455 56 and associated intrusions in the Proterozoic platform of east- ern North Greenland – a study of the interaction between intrusive basic magma and sialic crust. Journal of Petrology 24, 605–634. Kalsbeek, F. & Jepsen, H.F. 1984: The late Proterozoic Zig-Zag Dal Basalt Formation of eastern North Greenland. Journal of Petrology 25, 644–664. 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. Kalsbeek, F., Nutman, A.P., Escher, J.C., Friderichsen, J.D., Hull, J.M., Jones, K.A. & Pedersen, S.A.S. 1999: Geochronology of granitic and supracrustal rocks from the northern part of the East Greenland Caledonides: ion microprobe U-Pb zircon ages. Geology of Greenland Survey Bulletin 184, 31–48. Kalsbeek, F., Thrane, K., Nutman, A.P. & Jepsen, H.F. 2000: Late Mesoproterozoic metasedimentary and granitic rocks in the Kong Oscar Fjord region, East Greenland Caledonian fold belt: evidence for Grenvillian orogenesis? Journal of the Geologi- cal Society (London) 157, 1215–1225. Kalsbeek, F., Jepsen, H.F. & Nutman, A.P. 2001a: From source migmatites to plutons: tracking the origin of c. 435 Ma gran- ites in the East Greenland Caledonian orogen. Lithos 57, 1– 21. Kalsbeek, F., Jepsen, H.F. & Jones, K.A. 2001b: Geochemistry and petrogenesis of S-type granites in the East Greenland Caledonides. Lithos 57, 91–109. Leslie, A.G. & Nutman, A.P. 2000: Episodic tectono-thermal activ- ity in the southern part of the East Greenland Caledonides. Geology of Greenland Survey Bulletin 186, 42–49. Leslie, A.G. & Nutman, A.P. 2003: Evidence for Neoproterozoic orogenesis and early high temperature Scandian deformation events in the southern East Greenland Caledonides. Geologi- cal Magazine 140, 309–333. Pedersen, S.A.S., Craig, L.E., Upton, B.G.J., Rämö, O.T., Jepsen, H.F. & Kalsbeek, F. 2002: Palaeoproterozoic (1740 Ma) rift- related volcanism in the Hekla Sund region, eastern North Greenland: field occurrence, geochemistry and tectonic set- ting. Precambrian Research 114, 327–346. Peel, J.S. 1980: Geological reconnaissance in the Caledonian fore- land of eastern North Greenland with comments on the Cen- trum Limestone. Rapport Grønlands Geologiske Undersøgel- se 99, 61–72. Peel, J.S. & Smith, M.P. 1988: The Wandel Valley Formation (Early– Middle Ordovician) of North Greenland and its correlatives. In: Peel, J.S. (ed.): Cambrian–Jurassic fossils, trace fossils and stratigraphy from Greenland. Rapport Grønlands Geologiske Undersøgelse 137, 61–92. Rasmussen, J.A. & Smith, M.P. 1996: Lower Palaeozoic carbon- ates in eastern North Greenland, and the demise of the ‘Sæfaxi Elv nappe’. Bulletin Grønlands Geologiske Undersøgelse 172, 49–54. Rasmussen, J.A. & Smith, M.P. 2001: Conodont geothermometry and tectonic overburden in the northernmost East Greenland Caledonides. Geological Magazine 138, 687–698. Rejebian, V.A., Harris, A.G. & Huebner, J.S. 1987: Conodont color and alteration. An index to regional metamorphism, contact metamorphism and hydrothermal alteration. Bulletin Geologi- cal Society of America 99, 471–479. Smith, M.P. 2000: Cambro-Ordovician stratigraphy of Bjørnøya and North Greenland: constraints on tectonic models for the Arctic Caledonides and the Tertiary opening of the Green- land Sea. Journal of the Geological Society (London) 157, 459–470. Smith, M.P., Sønderholm, M. & Tull, S.J. 1989: The Morris Bugt Group (Middle Ordovician – Silurian) of North Greenland and its correlatives. Rapport Grønlands Geologiske Undersø- gelse 143, 5–20. Smith, M.P., Soper, N.J., Higgins, A.K., Rasmussen, J.A. & Craig, L.E. 1999: Palaeokarst systems in the Neoproterozoic of east- ern North Greenland in relation to extensional tectonics on the Laurentian margin. Journal of the Geological Society (Lon- don) 156, 113–124. Smith, M.P., Higgins, A.K., Soper, N.J. & Sønderholm, M. 2004a: The Neoproterozoic Rivieradal Group of Kronprins Christian Land, eastern North Greenland. In: Higgins, A.K. & Kalsbeek, F. (eds): East Greenland Caledonides: stratigraphy, structure and geochronology. Geological Survey of Denmark and Green- land Bulletin 6, 29–39 (this volume). Smith, M.P., Rasmussen, J.A., Robertson, S., Higgins, A.K & Leslie A.G. 2004b: Lower Palaeozoic stratigraphy of the East Green- land Caledonides. In: Higgins, A.K. & Kalsbeek, F. (eds): East Greenland Caledonides: stratigraphy, structure and geochro- nology. Geological Survey of Denmark and Greenland Bulle- tin 6, 5–28 (this volume). Sønderholm, M. & Jepsen, H.F. 1991: Proterozoic basins of North Greenland. In: Peel, J.S. & Sønderholm, M. (eds): Sediment- ary basins of North Greenland. Bulletin Grønlands Geolo- giske Undersøgelse 160, 49–69. Steiger, R.H., Hansen, B.T., Schuler, C., Bär, M.T. & Henriksen, N. 1979: Polyorogenic nature of the southern Caledonian fold belt in East Greenland. Journal of Geology 87, 475–495. Strachan, R.A. & Tribe, I.R. 1994: Structure of the Storstrømmen shear zone, eastern Hertugen af Orléans Land, North-East Greenland. In: Higgins, A.K. (ed.): Geology of North-East Greenland. Rapport Grønlands Geologiske Undersøgelse 162, 103–112. Watt, G.R., Kinny, P.D. & Friderichsen, J.D. 2000: U-Pb geochro- nology of Neoproterozoic and Caledonian tectonothermal events in the East Greenland Caledonides. Journal of the Geological Society (London) 157, 1031–1048. GEUS Bulletin 6.pmd 10-02-2005, 09:5456