ANDRILL Research and Publications Copyright (c) 2013 University of Nebraska - Lincoln All rights reserved. http://digitalcommons.unl.edu/andrillrespub Recent documents in ANDRILL Research and Publications en-us Thu, 02 May 2013 01:33:00 PDT 3600 The upper lithostratigraphic unit of ANDRILL AND-2A core (Southern McMurdo Sound, Antarctica): Local Pleistocene volcanic sources, paleoenvironmental implications and subsidence in the southern Victoria Land Basin http://digitalcommons.unl.edu/andrillrespub/56 http://digitalcommons.unl.edu/andrillrespub/56 Tue, 30 Apr 2013 11:04:53 PDT We report results from the study of the uppermost 37 m of the Southern McMurdo Sound (SMS) AND-2A drill core, corresponding to the lithostratigraphic unit 1 (LSU 1), the most volcanogenic unit within the core. We present data on the age, composition, volcanological and depositional features of the volcanic sedimentary and tephra deposits of LSU 1 and discuss their source, mechanisms of emplacement and environment of deposition.

Sedimentary features and compositional data indicate shallow water sedimentation for the whole of LSU 1. Most of LSU 1 deposits are a mixture of near primary volcanic material with minor exotic clasts derived from the Paleozoic crystalline basement rocks. Among volcanic materials, glassy particles are the most abundant. They were produced by mildly explosive basaltic eruptions occurring in subaerial and subaqueous environments. The Dailey Islands group, 13 km south-southwest of the SMS drill-site, has been identified as a possible source for the volcanics on the basis of similarity in composition and age. 40Ar–39Ar laser step-heating analyses on a lava sample from Juergens Island yields an age of 775 ± 22 ka. Yet because of the minimal reworking features of vitriclasts, preservation of fragile structures in volcaniclastic sediments and evidence for volcanic seamounts to the north of the Dailey Islands, it is likely that some of the material originated also from vents close to the drill-site.

Evidence for local volcanic sources and for deposition of sediments in a shallow marine environment provides indications about the local paleogeography and implications for the subsidence history of the southern Victoria Land Basin from Pleistocene to Recent.

]]> Paola Del Carlo et al. Evolution with depth from detrital to authigenic smectites in sediments from AND-2A drill core (McMurdo Sound, Antarctica) http://digitalcommons.unl.edu/andrillrespub/55 http://digitalcommons.unl.edu/andrillrespub/55 Fri, 08 Mar 2013 13:33:59 PST We have examined the nature and origin of smectites in glaciomarine sediments of the AND-2A drill core (McMurdo Sound, Antarctica) by means of X-ray diffraction (XRD) analyses on the clay fraction, field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM) observations and SEM-EDS microanalyses on smectite particles. Relying on the smectite variation throughout the drill core it was possible to split the sequence into three units. Smectites throughout the core are either detrital or authigenic. Detrital smectites are close to montmorillonite-beidellite in composition while newly-formed smectites frequently have higher Fe-Mg contents and intermediate compositions between the saponite and nontronite field, with lower amounts in the montmorillonite-beidellite field. In the upper sedimentary sections (Unit I, and Unit II, 36–440 mbsf, 0.7–16.5 Ma) smectites are interpreted to be predominantly detrital, whereas in the lower portion of the core (Unit III, 440–1123.20 mbsf, 16.5–20.2 Ma) authigenic smectites are the most common feature. The predominance of mica, the abundance of chlorite, and the nature of smectites in the upper units indicate physical weathering under cold and dry climate, and a dominant provenance for the clay minerals from the Transantarctic Mountains. Smectites in the lower unit are considered mostly authigenic and they are most likely to be the result of early diagenetic processes, being formed from the alteration of volcanic material (glass, pyroxenes and feldspars) and/or through precipitation from fluids of a possible hydrothermal origin. Our survey attests to the importance of discriminating between a detrital and authigenic nature of smectites as the occurrence of authigenic clay minerals in ancient sedimentary successions might lead to incorrect paleoclimatic interpretations, since they can be affected by diagenetic processes, thus obliterating the climatic signal.

]]> Francesco Iacoviello et al. Chemostratigraphy of the early Pliocene diatomite interval from MIS AND-1B core (Antarctica): Paleoenvironment implications http://digitalcommons.unl.edu/andrillrespub/54 http://digitalcommons.unl.edu/andrillrespub/54 Wed, 27 Feb 2013 09:52:12 PST The AND-1B drill core (1285 m-long) was recovered, inside the ANDRILL (ANtarctic geological DRILLing) Program, during the austral summer of 2006/07 from beneath the floating McMurdo Ice Shelf. Drilling recovered a stratigraphic succession of alternating diamictites, diatomites and volcaniclastic sediments spanning about the last 14 Ma. A core portion between 350 and 480 mbsf, including a 80 m-thick diatomite interval recording the early Pliocene warming event, was investigated in term of opal biogenic content and element geochemistry. Across the diatomite interval, in spite of the lithological uniformity, a fluctuating biogenic opal profile mirrors the δ18O record, testifying a decrease in productivity when temperature drops as a consequence of small glacial fluctuations. The comparison of biogenic opal data with Chaetoceros spp. abundances from Konfirst et al. (2012) documents alternations between periods of high primary productivity in stratified surface waters and of enhanced terrigenous input in ice-free conditions. Cluster analysis discriminates elements associated to terrigenous input from those subject to biogenic control. Further separation in sub-cluster was interpreted in term of different element response to changes in provenance but also to depositional/ early diagenetic conditions at the seafloor. Whilst K and Ti are related to different sediment sources confirming previous studies from the same interval, V, Zn and, to a lesser extent, Fe, document reducing/anoxic conditions during the diatomites deposition (in particular in 400–460 mbsf interval). Mg, Sr and Mn contents are related to authigenic carbonate precipitation whilst Ba is interested by non-steady-state processes leading to local peaks of barium below the sulfate-rich/sulfate-poor pore water boundary where generally the low degree of barite saturation is responsible for Ba remobilization. Such alteration in depositional dynamics, responsible of the precipitation of an oxygen-depleted barium phase, was probably induced by change in sedimentation rate and/or in paleoenvironmental conditions.

]]> Giovanna Scopelliti et al. Provenance of Pleistocene sediments in the ANDRILL AND-1B drillcore: Clay and heavy mineral data http://digitalcommons.unl.edu/andrillrespub/53 http://digitalcommons.unl.edu/andrillrespub/53 Mon, 02 Apr 2012 14:28:45 PDT The cryosphere in the McMurdo Sound region has undergone significant modifications during the last 1 Ma. Consequently, the sedimentary sequences underlying the modern McMurdo Ice-Shelf provide geological data to reconstruct variations in transport and depositional mechanisms of terrigenous material due to variations in ice sheet extension, grounding line position and main icestream flow directions during glacial and interglacial periods. The present study aims to investigate the clay and heavy mineral assemblages of the late Pleistocene subglacial and glaciomarine sediments recovered during the ANDRILL-McMurdo Ice Shelf Project in Windless Bight (South of Ross Island). The analyses show that the sediments are a mix of detritus from the McMurdo Volcanic Group (MVG) and the Transantarctic Mountains (TAM) from the south and west. MVG-derived minerals prevail with respect to TAM-derived minerals. The down-core mineralogical variations are determined by changes in the source rocks and the sedimentary processes. Sediments at the drill site are nourished by ice coming from the South which delivered rocks from the McMurdo Volcanic region; the enrichment of a TAM component in massive diamictites testifies that the ice sheet collected debris from the Transantarctic Mountains. When open marine conditions prevailed, only sediments from a local source (i.e. McMurdo volcanics) were deposited.

]]> Giovanna Giorgetti et al. <sup>40</sup>Ar–<sup>39</sup>Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): Correlations with the Erebus Volcanic Province and implications for the age model of the core http://digitalcommons.unl.edu/andrillrespub/52 http://digitalcommons.unl.edu/andrillrespub/52 Thu, 28 Apr 2011 14:18:32 PDT The AND-2A drillcore (Antarctic Drilling Program—ANDRILL) was successfully completed in late 2007 on the Antarctic continental margin (Southern McMurdo Sound, Ross Sea) with the aim of tracking ice proximal to shallow marine environmental fluctuations and to document the 20-Ma evolution of the Erebus Volcanic Province. Lava clasts and tephra layers from the AND-2A drillcore were investigated from a petrographic and stratigraphic point of view and analyzed by the 40Ar–39Ar laser technique in order to constrain the age model of the core and to gain information on the style and nature of sediment deposition in the Victoria Land Basin since Early Miocene. Ten out of 17 samples yielded statistically robust 40Ar–39Ar ages, indicating that the AND-2A drillcore recovered ≤230 m of Middle Miocene (~128–358 m below sea floor, ~11.5–16.0 Ma) and >780 m of Early Miocene (~358–1093 m below sea floor, ~16.0–20.1 Ma). Results also highlight a nearly continuous stratigraphic record from at least 358 m below sea floor down hole, characterized by a mean sedimentation rate of ~19 cm/ka, possible oscillations of no more than a few hundreds of ka and a break within ~17.5–18.1 Ma. Comparison with available data from volcanic deposits on land, suggests that volcanic rocks within the AND-2A core were supplied from the south, possibly with source areas closer to the drill site for the upper core levels, and from 358 m below sea floor down hole, with the “proto-Mount Morning” as the main source.

]]> Gianfranco Di Vincenzo et al. Polar research: School of rock http://digitalcommons.unl.edu/andrillrespub/51 http://digitalcommons.unl.edu/andrillrespub/51 Mon, 25 Apr 2011 11:30:26 PDT As Antarctica’s ice teams continue to hunt for the oldest ice their drills will reach, a smaller band of rockhounds is on a similar quest to plug the gaps in the geological record. The team now has a core that promises fresh insight into how Antarctica’s ice waxed and waned over the past few million years. On December 26, 2006, a US$30-million international project called ANDRILL pulled up the final piece of a core from beneath the Ross ice shelf. Previous coring efforts have offered peeks into Antarctica’s deep history — back as far as 34 million years when the continent was first covered in ice. But the new core fills a gap in the ice shelf’s history, and sets a new Antarctic record for drilling depth. The period covered by the core — from the present to more than 5 million years ago — seems to be quite active. Preliminary analysis has revealed thick layers of a greenish rock interspersed throughout the core. This is an indication of open-water conditions, suggesting that the Ross shelf retreated and then advanced at least 50 times within the past 5 million years. With this nearly unbroken record, scientists can explore the history of the shelf in unprecedented detail.

]]> Alexandra Witze Sediment cores reveal Antarctica’s warmer past http://digitalcommons.unl.edu/andrillrespub/50 http://digitalcommons.unl.edu/andrillrespub/50 Mon, 25 Apr 2011 10:52:13 PDT A unique drilling project in the western Ross Sea has revealed that Antarctica had a much more eventful climate history than previously assumed. A new sediment core hints that the western part of the now-frozen continent went through prolonged ice-free phases — presumably offering a glimpse of where our warming world might be heading. Researchers reported initial results from ANDRILL, a US$30-million international drilling project, on April 16 at the assembly of the European Geosciences Union in Vienna. During the past two years, the team has extracted two cores, each containing some 1,200 meters of sediment, from the seabed below the vast Ross Ice Shelf, a floating extension of the West Antarctic Ice Sheet. Together, the cores provide an almost uninterrupted 17-million-year record of Antarctica’s climatic past.

]]> Quirin Schiermeier Provenance signatures of the Antarctic Ice Sheets in the Ross Embayment during the Late Miocene to Early Pliocene: The ANDRILL AND-1B core record http://digitalcommons.unl.edu/andrillrespub/49 http://digitalcommons.unl.edu/andrillrespub/49 Mon, 25 Apr 2011 10:41:05 PDT Significant down-core modal and compositional variations are described for granule- to cobble-sized clasts in the Early Pliocene to Middle/Late Miocene sedimentary cycles of the AND-1B drill core at the NW edge of the Ross Ice Shelf (McMurdo Sound).

Long-term shifts in compositional patterns outline an evolving provenance which is interpreted as reflecting the combined effects and complex interactions among variations in ice volume, ice flow patterns and paleogeographic changes linked to the local tectonic and volcanic activity. High-frequency variations and the petrological features of the basement clast fraction provide direct information about the potential source regions during both glacial maxima and minima. Provenance of the more distal material is identified in the region between Ross Island and the Skelton–Mulock glacier area (South Victoria Land) (Plio-Late Miocene section) and in the Darwin Glacier catchment (Miocene section). The provenance shifts can be discussed for their implications on ice dynamic models for the glacial evolution recorded in the western Ross Embayment. Reconstructed ice flow directions are consistent with the glaciological models for the Last Glacial Maximum, and the provenance data corroborate the contributions of both the East and West Antarctic Ice Sheets in influencing the modifications of the ice flow pattern of grounded ice in the western Ross Embayment in Miocene to Pleistocene time.

]]> Franco M. Talarico et al. Late Cenozoic oscillations of Antarctic ice sheets revealed by provenance of basement clasts and grain detrital modes in ANDRILL core AND-1B http://digitalcommons.unl.edu/andrillrespub/48 http://digitalcommons.unl.edu/andrillrespub/48 Tue, 19 Apr 2011 12:19:35 PDT Petrological investigations of the sand fraction and of granule- to cobble-sized clasts in the Plio-Pleistocene sedimentary cycles of the AND-1B drill core at the NW edge of the Ross Ice Shelf (McMurdo Sound) highlight significant down-core modal and compositional variations. These variations provide: (i) direct information about potential source regions during both glacial maxima and minima; and (ii) evidence of an evolving provenance, documented by long-term shifts in compositional patterns that can be interpreted as reflecting variations in ice volume and ice sheet thermal regimes and changes in paleogeography related to the emergence of several volcanic centers during the deposition of the drill core over the past ca. 3.5 Ma.

The most significant change in diamictite provenance (identified at 82.7 meters below the sea floor, mbsf), coincides with a change in sedimentary cycle architecture from sequences that are dominated by diamictites (Mid-Late Pleistocene, above 82.7 mbsf) to sequences characterized by cycles of diamictite (subglacial) and diatomite (open-marine) deposition (Pliocene, below 82.7 mbsf). In the Mid-Late Pleistocene glacial/interglacial cycles diamictites show high amounts of Skelton–Mulock sourced clasts, supplied from both basement and overlying Beacon and Ferrar supergroups, and they also include a variable contribution from reworking of glacial sediments that were deposited during earlier glacial activity.

In the Pliocene to early Pleistocene diatomite–diamictite cycles basement clast compositions indicate the same provenance (Mulock–Skelton) but the main debris load was picked up from volcanic centers in the McMurdo Sound area. Similarly, associated glacial minima sediments (i.e., diatomite intervals) are dominated by volcanic clasts suggesting calving of glaciers from Ross Island or the Koettlitz Glacier region during interglacials.

In agreement with previous glaciological reconstructions and numerical ice sheet models, the provenance of glacially transported material is firmly identified in the region between Ross Island and the Skelton–Mulock glacier area (South Victoria Land). The reconstructed ice directions and ice dynamic model are comparable to the configurations proposed for the grounded ice expansion within the McMurdo Sound during the Last Glacial Maximum, and they are also consistent with ice-flow patterns previously reconstructed for Pliocene and Pleistocene glacial settings in the region.

Supplemental material (MIS CORE - MODAL VARIATIONS IN CLAST LITHOLOGIES) is included in the document and also attached (below) as a spreadsheet file.

]]> Franco M. Talarico et al. Downhole Measurements in the AND-2A Borehole, ANDRILL Southern McMurdo Sound Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/47 http://digitalcommons.unl.edu/andrillrespub/47 Tue, 19 Apr 2011 10:43:21 PDT Under the framework of the ANDRILL Southern McMurdo Sound (SMS) Project successful downhole experiments were conducted in the 1138.54 metre (m)-deep AND-2A borehole. Wireline logs successfully recorded were: magnetic susceptibility, spectral gamma ray, sonic velocity, borehole televiewer, neutron porosity, density, calliper, geochemistry, temperature and dipmeter. A resistivity tool and its backup both failed to operate, thus resistivity data were not collected. Due to hole conditions, logs were collected in several passes from the total depth at ~1138 metres below sea floor (mbsf) to ~230 mbsf, except for some intervals that were either inaccessible due to bridging or were shielded by the drill string. Furthermore, a Vertical Seismic Profile (VSP) was created from ~1000 mbsf up to the sea floor. The first hydraulic fracturing stress measurements in Antarctica were conducted in the interval 1000-1138 mbsf. This extensive data set will allow the SMS Science Team to reach some of the ambitious objectives of the SMS Project. Valuable contributions can be expected for the following topics: cyclicity and climate change, heat flux and fluid flow, seismic stratigraphy in the Victoria Land Basin, and structure and state of the modern crustal stress field.

]]> T. Wonik et al. Preliminary Integrated Chronostratigraphy of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/46 http://digitalcommons.unl.edu/andrillrespub/46 Tue, 19 Apr 2011 10:36:45 PDT Chronostratigraphic data available for the preliminary age model for the upper 700 m for the AND-1B drill core include diatom biostratigraphy, magnetostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr ages on calcareous fossil material, and surfaces of erosion identifi ed from physical appearance and facies relationships recognised in the AND-1B drill core. The available age data allow a relatively well-constrained age model to be constructed for the upper 700 m of the drill core. Available diatom biostratigraphic constraints and 40Ar/39Ar ages allow a unique correlation of ~70% of the AND- 1B magnetic polarity stratigraphy with the Geomagnetic Polarity Time Scale (GPTS). Unique correlation is not possible in several coarse diamictite intervals with closely spaced glacial surfaces of erosion and sparse microfl ora. However, the age model indicates relatively rapid (up to 1 m/k.y.) and continuous accumulation of intervening fi ner grained diatomaceous intervals punctuated by several half- to millionyear hiatuses representing more than half of the last 7 m.y. in the AND-1B record. The mid- to late Pleistocene is represented by superimposed diamictite units separated from upper Pliocene alternating diamictites/diatomites by a ~1 m.y. hiatus co-incident with a regionally correlated seismic reflection surface. A c. 100 m-thick diatomite represents a signifi cant portion of the early Pliocene record in the AND-1B drill core. Strata below ~620 m are late Miocene in age; however, biostratigraphic constraints are absent below 586 m and correlation with the GPTS is relatively unconstrained. At the time of writing, the only chronostratigraphic data available below 700 mbsf include three 40Ar/39Ar ages on volcanic clasts from near 1280 mbsf affording a maximum depositional age of 13.57 Ma for the base of the AND-1B drill core.

]]> G. S. Wilson et al. Palaeomagnetism of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/45 http://digitalcommons.unl.edu/andrillrespub/45 Tue, 19 Apr 2011 10:26:34 PDT Preliminary palaeomagnetic data are presented for the AND-1B drill core. A total of 1309 samples were collected from the drill core immediately following recovery and splitting. Natural remanent magnetisation (NRM) and bulk magnetic susceptibility data were determined for all samples using a Molspin spinner magnetometer and Bartington Instruments susceptibility bridge, respectively, immediately after collection. Polarity was determined for the upper 700 m of the drill core from 615 stepwise alternating field (AF) and thermally demagnetized samples with an average sample spacing of ~80 cm between 32 and 240 mbsf and ~2 m between 240 and 700 mbsf. Stepwise demagnetised samples were measured on 2G Enterprises long-core cryogenic magnetometers at the University of Otago and the Istituto di Geofisica e Vulcanologia. A magnetic polarity zonation was constructed for the interval between 32.33 and 700 mbsf, with roughly equal normal and reversed polarity represented. Above 32.33 mbsf, poorly consolidated diamictite strata prevented sample collection. The remaining record was subdivided into 15 magnetozones (8 normal and 7 reversed). Magnetozone boundaries are defined at the midpoint between samples of opposite polarity or by samples with transitional polarity. It was not possible to isolate characteristic remanence (ChRM) directions on orthogonal component plots and hence polarity for several ~10 m intervals in the core. Future work will include determination of a polarity zonation for the lower 585 m of the drill core and halving data spacing between 240 and 700 mbsf.

]]> G. S. Wilson et al. Fracture Logging of the AND-1B Core, McMurdo Ice Shelf Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/44 http://digitalcommons.unl.edu/andrillrespub/44 Tue, 19 Apr 2011 10:22:24 PDT Over 4300 natural and induced fractures were logged in AND-1B drill core. Induced fractures include steeply dipping, petal, petal-centreline, and core-edge induced fractures (n=421) which reach a maximum density of 5 fractures/metre. Subhorizontal induced extension fractures are also abundant. Natural fractures (n=1485) occur in Miocene to Pleistocene age strata and include faults, brecciated zones, veins and sedimentary intrusions. Kinematic indicators document dominant normal faulting, although reverse faults are also present. Vein types include slickenfiber veins along faults, opening-mode fibrous veins, pressure shadows on clast margins, and complex microvein webs within fault zones.

]]> Terry J. Wilson et al. Sequence stratigraphy of the ANDRILL AND-2A drillcore, Antarctica: A long-term, ice-proximal record of Early to Mid-Miocene climate, sea-level and glacial dynamism http://digitalcommons.unl.edu/andrillrespub/43 http://digitalcommons.unl.edu/andrillrespub/43 Mon, 18 Apr 2011 14:57:09 PDT Present understanding of Antarctic climate change during the Early to Mid-Miocene, including major cycles of glacial expansion and contraction, relies in large part on stable isotope proxies from deep sea core drilling. Here, we summarize the lithostratigraphy of the ANDRILL Southern McMurdo Sound Project drillcore AND-2A. This core offers a hitherto unavailable ice-proximal stratigraphic archive from a high-accommodation continental margin setting, and provides clear evidence of repeated fluctuations in climate, ice expansion/contraction and attendant sea-level change over the period c. 20.2–14.2 Ma, with a more fragmentary record of Late Miocene and Pliocene time. The core is divided into seventy-four high-frequency (fourth- or fifth-order) glacimarine sequences recording repeated advances and retreats of glaciers into and out of the Victoria Land Basin. The section can be resolved into thirteen longer-term, composite (thirdorder) sequences, which comprise packages of higher frequency sequences that show a consistent stratigraphic stacking pattern (Stratigraphic Motif). The distribution of the six recognized motifs indicates intervals of less and more ice-proximal, and temperate to subpolar/polar climate, through the Miocene period. The core demonstrates a dynamic climate regime throughout the Early to Mid-Miocene that may be correlated to some previously-recognized events such as the Mid-Miocene Climatic Optimum, and provides a detailed reference point from which to evaluate stable isotope proxy records from the deep-sea.

]]> Christopher R. Fielding et al. Preliminary chronostratigraphy for the upper 700 m (upper Miocene – Pleistocene) of the AND-1B drillcore recovered from beneath the McMurdo Ice Shelf, Antarctica http://digitalcommons.unl.edu/andrillrespub/42 http://digitalcommons.unl.edu/andrillrespub/42 Mon, 18 Apr 2011 14:51:32 PDT Chronostratigraphic data available for the preliminary age model for the upper 700 m for the AND-1B drill core include diatom biostratigraphy, magnetostratigraphy, 40Ar/39Ar ages on volcanic material, 87Sr/86Sr ages on calcareous fossil material, and surfaces of erosion identified from physical appearance and facies relationships recognized in the AND-1B drill core. The available age data allow a relatively well-constrained age model to be constructed for the upper 700 m of the drill core. Available diatom biostratigraphic constraints and 40Ar/39Ar ages allow a unique correlation of ~70% of the AND-1B magnetic polarity stratigraphy with the Geomagnetic Polarity Time Scale (GPTS). Unique correlation is not possible in several coarse diamictite intervals with closely spaced glacial surfaces of erosion and sparse microflora. However, the age model indicates relatively rapid (up to 1m / k.y.) and continuous accumulation of intervening finer grained diatomaceous intervals punctuated by several half to million year hiatuses representing more than half of the last 7 m.y. in the AND-1B record. The mid-late Pleistocene is represented by superimposed diamictite units separated from upper Pliocene alternating diamictites / diatomites by a ~ 1 m.y. hiatus co-incident with a regionally correlated seismic reflection surface. A c. 100 m thick diatomite represents a significant portion of the early Pliocene record in the AND-1B drillcore. Strata below ~620 m are late Miocene in age, however biostratigraphic constraints are absent below 586 m and correlation with the GPTS is relatively unconstrained.

]]> G. S. Wilson et al. Palaeontological Characterisation and Analysis of the AND-2A Core, ANDRILL Southern McMurdo Sound Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/41 http://digitalcommons.unl.edu/andrillrespub/41 Mon, 18 Apr 2011 14:39:09 PDT The palaeontological yield of the 1138.54 metre-long AND-2A sedimentary rock core provides unique documentation of Neogene environments in the Ross Sea region of Antarctica. Especially important is the biological legacy of the climatically crucial ‘mild’ middle Miocene phase. Diatom-bearing units provide key information for stratigraphic intervals never previously recovered from locations proximal to the Antarctic continent and constrain the age model for the AND-2A core. Benthic calcareous (and agglutinated) foraminifera were present at many levels; remarkable is the occurrence of planktonic taxa only seldom found in the Neogene nearshore record of the Ross Sea region. The sporadic occurrence of calcareous dinoflagellate remains (thoracosphaerids) is consistent with warmer-than-present seawater during the Miocene. Marine palynomorphs are almost ubiquitous, although their abundance and diversity are variable. Pollen and spores from the middle Miocene section suggest a mossy tundra vegetation and represent the first stratigraphically-constrained record of terrestrial vegetation in Victoria Land during this time. Fragments of lignin-rich organic matter (huminite-vitrinite and inertinite groups) are particularly predominant during the Miocene climatic optimum, and continue into the Pliocene. Macrofossils are reasonably common throughout the core. Polychaete worm tubes were almost ubiquitous. Especially remarkable is the bivalve record (mainly pectinids), with 4-5 different taxa pointing out a mild climatic situation in the Miocene nearshore.

]]> M. Taviani et al. New Seismic Methods to Support Sea-Ice Platform Drilling http://digitalcommons.unl.edu/andrillrespub/40 http://digitalcommons.unl.edu/andrillrespub/40 Mon, 18 Apr 2011 14:26:41 PDT The ANtarctic geological DRILLing Program (ANDRILL) is currently a consortium of five nations (Germany, Italy, New Zealand, the United Kingdom, and the United States of America). By drilling, coring and analyzing stratigraphic archives along the Antarctic continental margin, ANDRILL pursues its primary goal of better understanding the role the Antarctic cryosphere plays in the global climate system (Harwood et al., 2006). The ANDRILL drilling system was developed to operate on both ice shelf and sea-ice platforms (Harwood et al., 2006; Falconer et al., 2007; Naish et al., 2007; Florindo et al., 2008). While thick multiyear sea ice provides stable and safe drilling platforms, identifying drilling targets in regions where these sea-ice conditions occur can be problematic due to a paucity of marine seismic reflection data because near-constant sea ice limits shop access (Fig. 1.). In response to this problem ANDRILL developed new over-sea-ice seismic methods to extend seismic reflection data coverage to regions of multiyear sea ice.

]]> M. A. Speece et al. Palaeontologic Characterisation and Analysis of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/39 http://digitalcommons.unl.edu/andrillrespub/39 Mon, 18 Apr 2011 14:14:03 PDT Fossils provide key data sets for the interpretation of the AND-1B core. Calcareous plankton and benthos provide the basis for palaeoenvironmental interpretations of both surface and bottom waters. Calcareous fossils are rare throughout, but occurrences noted are significant. Some calcareous fossils provide potential for age control via 86Sr/87Sr, and palaeoenvironmental information may come from Mg/Ca ratios as well as oxygen and carbon isotopes. Organic-walled microfossils provide an index of reworking and transport, as well as the identifi cation of a possible in situ Pliocene assemblage of previously unknown marine palynomorphs. Diatoms are abundant in the core, with diatom-rich sediments constituting nearly half the upper 600 m of core, subdivided into 13 diatomaceous units, ranging in thickness from under 1 m to nearly 100 m. Diatoms provide biostatigraphic age control, but calibration to the Southern Ocean zonation is limited by ecologic exclusion of many taxa and previously undocumented diachrony among other taxa. A new, high-resolution diatom biostratigraphy for the Antarctic continental shelf is now under development. Diatoms provide the basis for numerous palaeoenvironmental applications, including providing a proxy for palaeotemperature and palaeo-sea ice, as well as palaeoproductivity. All results presented here are preliminary, and interpretations should be considered tentative, pending quantitative and more detailed qualitative follow-up analyses.

]]> R. Scherer et al. Antarctic Ice Sheet dynamics through the Neogene from evidence in the ANDRILL–McMurdo Ice Shelf Project drillcore (AND-1B) http://digitalcommons.unl.edu/andrillrespub/38 http://digitalcommons.unl.edu/andrillrespub/38 Mon, 18 Apr 2011 14:05:14 PDT ANDRILL completed its first season in 2006-07 drilling AND-1B through the McMurdo Ice Shelf (MIS) to a depth of 1,285m below the sea floor, a record for Antarctic margin drilling, with 99% recovery. The alternating glacial-interglacial sediment packages interbedded with volcanics provide a uniquely detailed record of Antarctic glacial and climatic change through the Neogene. This paper summarizes the initial characterization of lithofacies and syndepositional structures relevant to understanding the regime and dynamics of past Antarctic ice sheets based on the ANDRILL-MIS Initial Report. Results suggest that the Antarctic Ice Sheet was relatively cold with little basal melting in the middle Miocene and Pleistocene times but under a more dynamic and warmer polythermal glacial regime in late Miocene and Pliocene times. More detailed research, including a modeling component, is planned in order to understand the dynamics under these different regimes.

]]> R. D. Powell et al. Petrology and Geochemistry of the AND-1B Core, ANDRILL McMurdo Ice Shelf Project, Antarctica http://digitalcommons.unl.edu/andrillrespub/37 http://digitalcommons.unl.edu/andrillrespub/37 Mon, 18 Apr 2011 13:59:51 PDT This section reports preliminary data and results on petrology and geochemistry of AND-1B core.

]]> M. Pompilio et al.