Circum-Antarctic Coastal Environmental Shifts During the Late Quaternary Reflected by Emerged Marine Deposits

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35000 to 20000 yr sp, during Marine Isotope Stage 3 when extensive iceberg calving created a \u27meltwater lid\u27 over the Southern Ocean. The general absence of these marine species from 20000 to 8500 yr sp coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of wh ich have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. in view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone

Paleoclimatic and paleoceanographic records through Marine Isotope Stage 19 at the Chiba composite section, central Japan: A key reference for the EarlyeMiddle Pleistocene Subseries boundary

Marine Isotope Stage (MIS) 19 is an important analogue for the present interglacial because of its similar orbital configuration, especially the phasing of the obliquity maximum to precession minimum. However, sedimentary records suitable for capturing both terrestrial and marine environmental changes are limited, and thus the climatic forcing mechanisms for MIS 19 are still largely unknown. The Chiba composite section, east-central Japanese archipelago, is a continuous and expanded marine sedimentary succession well suited to capture terrestrial and marine environmental changes through MIS 19. In this study, a detailed oxygen isotope chronology is established from late MIS 20 to early MIS 18, supported by a U-Pb zircon age and the presence of the Matuyama–Brunhes boundary. New pollen, marine microfossil, and planktonic foraminiferal δ18O and Mg/Ca paleotemperature records reveal the complex interplay of climatic influences. Our pollen data suggest that the duration of full interglacial conditions during MIS 19 extends from 785.0 to 775.1 ka (9.9 kyr), which offers an important natural baseline in predicting the duration of the present interglacial. A Younger Dryas-type cooling event is present during Termination IX, suggesting that such events are linked to this orbital configuration. Millennial- to multi-millennial-scale variations in our δ18O and Mg/Ca records imply that the Subarctic Front fluctuated in the northwestern Pacific Ocean during late MIS 19, probably in response to East Asian winter monsoon variability. The climatic setting at this time appears to be related to less severe summer insolation minima at 65˚N and/or high winter insolation at 50˚N. Our records do not support a recently hypothesized direct coupling between variations in the geomagnetic field intensity and global/regional climate change. Our highly resolved paleoclimatic and paleoceanographic records, coupled with a well-defined Matuyama–Brunhes boundary (772.9 ka; duration 1.9 kyr), establish the Chiba composite section as an exceptional climatic and chronological reference section for the Early–Middle Pleistocene boundary.ArticleQuaternary Science Reviews 191: 406-430(2018)journal articl

Randomized Comparison Between Everolimus-Eluting Bioresorbable Scaffold and Metallic Stent: Multimodality Imaging Through 3 Years

Objectives: The aim of this study was to investigate the vascular responses and fates of the scaffold after bioresorbable vascular scaffold (BVS) implantation using multimodality imaging. Background: Serial comprehen

MARINE FOSSILS OF 30-40ka IN RAISED BEACH DEPOSITS, AND LATE PLEISTOCENE GLACIAL HISTORY AROUND LUTZOW-HOLM BAY, EAST ANTARCTICA

Radiocarbon ages of fossil marine organisms in raised beach deposits along the Soya Coast are clearly classified into two groups of 3-8ka and 33-42ka by Tandetron Accelerator Mass Spectrometry (TAMS). The older fossils are recognized on the Ongul Islands and the northernmost part of Langhovde, which are separated from the present ice sheet margin by a drowned glacial trough deeper than 500m. Some of the older molluscan fossils as well as the younger ones retain their living form in situ. These facts together with the deep continental shelf and a small amount of isostatic uplift of the Holocene raised beaches lead to the following conclusions for the region : 1) Marine transgression took place in the last interstadial and in the Holocene. 2) Major deglaciation took place by the last interstadial in the region. 3) Expansion of the ice sheet during the Last Glacial Maximum was slight, although its extent is still unknown. 4) Sea-level during the last interstadial was probably higher than that estimated from foraminiferal δ^O records in deep-sea sediments

OCCURRENCE AND DISTRIBUTION OF THE PLANKTONIC FORAMINIFER NEOGLOBOQUADRINA PACHYDERMA WITHIN ANNUAL AND PERENNIAL SEA ICE OF THE EASTERN PART OF LUTZOW-HOLM BAY, ANTARCTICA (17th Symposium on Polar Biology)

Annual and perennial sea ice cores, collected regularly for a period of one year at four fixed stations and one time each at 10 other stations in the eastern part of Ltitzow-Holm Bay, were investigated to elucidate characteristics of vertical distribution and abundance of planktonic foraminifers within sea ice. At Station A-5, situated about 3 km east of Syowa Station, the planktonic foraminifer Neogloboquadrina pachyderma with cytoplasm is present mainly within sections between 20 and 40 cm from the top of the cores. At Station A-2, located near Syowa Station, they are restricted predominantly to the lowermost 50 cm sections of the cores. At Station D, located about 20 km west of Syowa Station, they are distributed maximally within sections between 210 and 244 cm from the top of the cores. Considering the vertical distribution of foraminifers within sea ice and the time of freezing of sea ice, the main time of foraminiferal incorporation is estimated to be from mid-April to mid-May, that is, from austral late autumn to early winter. The foraminifers may probably become congregated in the uppermost part of the water column in order to feed on abundant diatoms during spring and summer. Until the onset of ice formation from late April to mid-May, they may still remain there and are likely to be accidentally incorporated into the sea ice

RADIOCARBON AGES OF MOLLUSCAN SHELL FOSSILS IN RAISED BEACH DEPOSITS ALONG THE EAST COAST OF LUTZOW-HOLM BAY, ANTARCTICA, DETERMINED BY ACCELERATOR MASS-SPECTROMETRY (16th Symposium on Polar Biology)

Radiocarbon ages of molluscan shell fossils embedded in raised beach deposits were measured by a Tandetron Accelerator Mass-Spectrometer at 12 locations in the Ongul Islands, Langhovde, and Skallen, all along the east coast of Lutzow-Holm Bay, Antarctica. Radiocarbon ages determined by Tandem Accelerator Mass-Spectrometry are 34350±550, 35040±480, 36180±630, and 37420±720 years B.P. for the Ongul Islands, 3660±100, 33410±510, 34940±460, and 37200±910 years B.P. for Langhovde, and 3180±90, 3790±180, 4720±90, and 7810±130 years B.P. for Skallen, respectively