AMQ29(2) 3 Negri 137-142NAG.pub Available online http://amq.aiqua.it ISSN (print): 2279-7327, ISSN (online): 2279-7335 Alpine and Mediterranean Quaternary, 29 (2), 2016, 137 - 142 THE FRONTE CANDIDATE SECTION FOR THE UPPER PLEISTOCENE GSSP: A SHORT REPORT Alessandra Negri 1, Fabio Florindo 2, Pontus C. Lurcock 2, Stefano Marabini 3, Caterina Morigi 4, Giuseppe Mastronuzzi 5, Costantino Vetrone 4, Gian Battista Vai 5 1 Dipartimento di Scienze della Vita e dell'Ambiente, Università Politecnica delle Marche, Ancona, Italy 2 INGV, Roma, Italy 3 Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università di Bologna, Bologna, Italy 4 Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy 5 Dipartimento di Scienze della Terra e Geoambientali, Università di Bari, Bari, Italy Corresponding author: A. Negri ABSTRACT: We report new data regarding the environmental history of the Taranto Area since MIS 11, which possibly led to the peculiar sediment preservation characterizing the Fronte Section. This section is a very promising candidate for the Upper Pleistocene GSSP. Some preliminary results achieved after the multiple core drilling at the Fronte locality (Taranto, Italy) are reported as well. Keywords: Upper Pleistocene, GSSP, Morphostratigraphic reconstruction, Paleomagnetism, Taranto 1. INTRODUCTION The Taranto area is located in the Apulian platform (Southern Italy) where a near 6 km-thick succession of Mesozoic neritic limestones (Calcari delle Murge) is unconformably overlain by the marine Pliocene to Pleis- tocene Gravina Calcarenite, the marine Pliocene to Middle Pleistocene Subapennine Clay or Blue Clay (Argille Subappennine), and marine terrace deposits of Middle to Late Pleistocene age. The marine terrace deposits generally show a characteristic unconformable contact with the underlying Blue Clay. Among them, those showing the presence of rhodalgal biocalcarenites containing warm-water “Senegalese” fauna (with the most known Persististrombus latus), and reefal build- ups bio-constructed by Cladocora caespitosa (Hearty & Dai Pra, 1992; Belluomini et al., 2002; Peirano et al., 2009 and references therein) date to the Last Intergla- cial Period. In particular, the outcrop at the Fronte local- ity has attracted the curiosity of several authors (Dai Pra & Stearns, 1977; Belluomini et al., 2002), providing ex- cellent exposure of an exceptionally preserved thick fine -grained sedimentary succession lying above the cal- carenites and reefal build-ups pertaining to the MIS 5.e, studied in detail by Antonioli et al., 2008, Amorosi et al., 2014 and Negri et al., 2015. The outcrop is located about 7 km east of Taranto (Fig. 1), along the coastal cliff surrounding the Mar Pic- colo (Fig. 1) close to the 65° Deposito Territoriale of the Aeronautica Militare, Taranto, Italy (40°28’32.57’’ N, 17° 18’48.07’’ E). The section is easily accessible by land and sea, because of the proximity to the harbour, and the km-sized outcrop guarantees easy sampling for comparison. Moreover, the conservation of the outcrop site is assured by a protocol under formalization be- tween Bari and Taranto Universities and the Administra- Fig. 1 - Location map of the Fronte Section Taranto, Italy (red dot). Work presented during the AIQUA scientific conferences "Waiting for the Nagoya INQUA XIX Congress", held in Florence, June 18 - 19, 2015 138 Negri A. et al. tion of the Italian Air Force, owner of the Fronte site. Finally, this site has been appointed as Special Geosite - Natural Monument CGP432 by the Puglia Region Ad- ministration who recognized its geological importance (Mastronuzzi et al., 2015). The stratigraphic section consists of 5 lithologic units described in Amorosi et al. (2014) and Negri et al. (2015) (Fig. 2). According to Negri et al. (2015), above a regional unconformity the MIS 5.e, these deposits are continuously sedimented showing an overall deepening- upward trend, from nearshore to inner-shelf (Cladocora- rich) and then middle to outer-shelf deposits. Above the Cladocora-rich units, the open-marine clays include the maximum flooding zone and show a continuous succes- sion of marly clays, 6.25 m thick (unit 4) in which stable isotopic, foraminiferal and palynological data, coupled with the U-Th dates, indicate that the whole MIS 5.e plateau (sensu Shackleton et al., 2003), up to the onset of the following sea-level fall, occurs in this section. Based on our previous studies, the present paper aims to 1) attempt the reconstruction of the evolution which led to the preservation of the Fronte Cliff and its peculiar sedimentary succession 2) provide a short re- port regarding the activities ongoing on the Fronte site, where a composite core was drilled in February 2015, on top of the outcropping section. 2. INFERRED EVOLUTION OF THE TARANTO AREA SINCE MIS 11 An attempt to reconstruct the geological history leading to the preservation of a fine sedimentary succes- sion above the calcarenites is based on the presence of two quasi-flat surfaces whose inner margins occur re- Fig. 2 - The Fronte Section stratigraphic log. 139 The Fronte candidate section for the Upper Pleistocene GSSP: ............ spectively at 28-35 and 35-55 m above sea level, as reported by Dai Pra & Stearns, 1977. They reported the higher and more landward as older than 300 ka (based on four U-Th dates yielding ages ranging from 250 to 350 ka). Such an age is consistent with Marine Isotope Stage (MIS) 9 or 11, the last being the longest (423,000- 362,000 ka) and warmest interglacial of the entire Qua- ternary Period, attaining the highest-known sea-level so far (Roberts et al., 2012). These features therefore sug- gest a low uplift rate at least during the last 125 ka, but possibly extended up to the last 400 ka, which is consis- tent with the hypothesis of a large bay (”the Taranto paleobay”) submerging a wide area around the present Mar Grande and Mar Piccolo during the last two major highstand peaks (MIS 5.e and MIS 11), (Fig. 3 based on the original drawings of Dai Pra & Stearns, 1977). In addition, the possibly MIS 11 to MIS 7 aged “Panchina” (calcarenites) terraces outcropping around the locality Masseria San Pietro (C in Fig. 3) were probably formed by alternate processes of marine abra- sion and fluvial incision for some tens of meters during the quite long and relatively stable MIS 11 or MIS 9 to MIS 5 time interval. The ensuing steep-walled Taranto palaeovalley was carved mostly through the Blue Clay (Argille Azzurre) substratum which developed mainly under control of a regional tectonic-related karst springs net, which is still active (Fonte Galeso). The rapid rise of MIS 5.e sea level submerged not only the MIS 6 emerged Taranto palaeovalley but probably also most of the Masseria S. Pietro MIS 11 terrace. In this view, de- pressed areas, such as Salina Grande (Fig. 3), accom- modated a mainly pelitic sedimentation (similar to unit 4 at the Fronte section in Amorosi et al., 2014 and Negri et al., 2015) whereas the most elevated areas were places of nearly continuous carbonate sedimentation (Panchina with Persististrombus latus and small colonies of Cladocora caespitosa). This morphostratigraphic interpretation permits us to attribute the Fronte cliff outcrop to the infill of MIS 5 sediment on the southernmost side of the “Taranto pale- Fig. 3 - Geologic geomorphologic map showing interpretative reconstruction of the MIS 5 (D) and MIS 11? (C) marine terraces and related coastlines in the Taranto area (modified after Dai Pra & Stearns, 1977; Mastronuzzi, 2001; Belluomini et al., 2002, Amorosi et al., 2014). A, pre-Middle Pleistocene calcareous substratum; B, Lower to Middle Pleistocene pelagic sediments (Blue Clay); C, Middle Pleistocene cal- careous marine deposits (MIS 11?); D, Upper Pleistocene marine deposits (MIS 5); E, Holocene alluvial and beach deposits; F, Reclaimed areas (19th and 20th centuries); G, Black dots: outcrops with “Senegalese” fauna. Numbers indicate elevation above sea level. Note that according to Dai Pra & Stearns (1977), the boundary between A and C is a paleo coastline older than 300 ka. ovalley”, depressed enough to be submerged early dur- ing Termination II, and protected seaward by sandy shoals and islands. In this way, above the unconformity bounding the upper part of the Blue Clay (Argille Subappennine Fm), the continuous coastal to marine succession (including most of MIS 5.e) was preserved from the subsequent low-stand dissection and erosion. After MIS 5, sea-level drop caused the palaeovalley’s distal segment to be re- incised during MIS 4 to MIS 2 and later filled by the Holocene clayey deposits cored in the Mar Piccolo ba- sin floor, creating the present morphology. Based on the detailed section reported in Dai Pra & Stearns (1977) and Belluomini et al. (2002) we infer that only a few areas (the Fronte locality and the Salina Grande seg- ment) became morphologically fossilized because they were protected from retrogressive erosion by the hard Panchina beds and, probably, some differential vertical movements. But this inferred evolution shows that the combination of low uplift rate with dissected palaeomor- phology provides, in this case, a particularly favourable host for sedimentation articulated in different facies and variable thicknesses, resulting in a unique candidate area for the Upper Pleistocene GSSP. 3. NEW CORES AND INVESTIGATIONS In this view of great potential to host a GSSP, a further improvement in the study of the section started from the preliminary paleomagnetic results published by Negri et al. (2015), suggesting the suitability of sedi- ments for a complete paleomagnetic study. This idea led us to drill multiple cores at the Fronte locality. The drill- ing was done on February 2015 at the top of the cliff 140 Negri A. et al. Fig. 4 - The MIS 5 “Taranto palaeobay” (blue area: MIS 5.e Ionian Sea; yellow area: MIS 11 or MIS9 + marine terrace; orange area: emerged pre-MIS 11 local substrate) (base map after Dai Pra & Stearns, 1977). Fig. 5 - The Fronte Cores Stratigraphic logs. 141 The Fronte candidate section for the Upper Pleistocene GSSP: ............ Ms. received: December 15, 2015 Final text received: May 5, 2016 where the section crops out, and yielded two cores (Fig. 5), showing the same lithological succession sampled in the field. We then sampled the cores (red bars in Fig. 5) using u-channels (1 m in length) and standard ~8 cm3 plastic cubes made up of non-magnetic material, and investigated the geomagnetic palaeosecular variation and relative palaeointensity recorded in these sedi- ments. Stepwise alternating-field treatment resulted in good demagnetization behaviour, with most samples showing a clear, major origin-directed magnetization component. The average inclination of around 57° is close to the geocentric axial dipole inclination of 60° for the sampling site, with the difference attributable to typi- cal inclination shallowing effects. The record contains several brief excursions of shallowed inclination. The most significant of these reaches inclinations of below 10°, and we tentatively correlate it with the Blake event. Relative palaeointensity exhibits a similarly dynamic behaviour across this interval. Integration of our palaeo- magnetic record with ongoing biostratigraphic work, and with other regional palaeomagnetic data, will provide a more thorough characterization of Late Pleistocene palaeosecular variation in southern Europe. 4. CONCLUSION In conclusion, we are intensifying the study of this section, but also we plan to go well beyond. In fact, al- though this section has to date received considerable attention from a multidisciplinary team, with basic infor- mation now available in the literature, further compre- hensive activity is required to evaluate its correlation with coeval continuous marine successions, thus permit- ting comparison with north-western European continen- tal records. This work is a necessary prerequisite for any proposal for this section as a GSSP candidate. 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Global and Planetary Change, 36, 151-155. 142 Negri A. et al. << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /None /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (U.S. Web Coated \050SWOP\051 v2) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Error /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.0000 /ColorConversionStrategy /CMYK /DoThumbnails false /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveDICMYKValues true /PreserveEPSInfo true /PreserveFlatness true /PreserveHalftoneInfo false /PreserveOPIComments true /PreserveOverprintSettings true /StartPage 1 /SubsetFonts true /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /CropColorImages true /ColorImageMinResolution 300 /ColorImageMinResolutionPolicy /OK /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 300 /ColorImageDepth -1 /ColorImageMinDownsampleDepth 1 /ColorImageDownsampleThreshold 1.50000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 300 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.50000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 1200 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.50000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile () /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False /CreateJDFFile false /Description << /ARA /BGR /CHS /CHT /CZE /DAN /DEU /ESP /ETI /FRA /GRE /HEB /HRV (Za stvaranje Adobe PDF dokumenata najpogodnijih za visokokvalitetni ispis prije tiskanja koristite ove postavke. 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