The Holocene fossil marine macrofauna of the Vestfold Hills, East Antarctica     

JOHN PICKARD 《Boreas: An International Journal of Quaternary Research》1985,14(2):189-202

The Holocene (< 10,000 years old) fossil marine macrofauna (molluscs, polychaetes, mammals and birds) of the Vestfold Hills, Antarctica (68°30'S, 78°00'E) is described. All species are extant, with circumantarctic or wider distributions and wide depth ranges. At Heidemann Bay, Pleistocene-age (> 30 ky old) shell fragments occur in a Holocene moraine. These are interpreted as being glacially reworked fossil shells. Holocene benthic estuarine and coastal molluses and serpulid worm tubes are abundant on the flanks of terraces above saline and hypersaline lakes. Extensive radiocarbon dating gives a chronology of these deposits which were not synchronous. Mummies of seals and penguins, which are concentrated on the shores of the saline lakes and scattered across the Hills, are of no use in dating geomorphological events. Marine fossils in moraines are difficult to interpret because they can be glacially-transported live or fossil shells, or deposited after wind transport. The fossil fauna has such a wide ecological range that it indicates only in general terms that for part of the Pleistocene and most of the Holocene, climatic conditions were broadly similar to the present.  相似文献   

>A-level fieldwork guide: Charnwood Forest     

JOHN B. MOSELEY 《Geology Today》1998,14(5):195-198

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Current continental palaeoclimatic research in the Nordic region (100 years since Gunnar Andersson 1909) – Introduction     

HEIKKI SEPPÄ  H. JOHN B. BIRKS  ANNE E. BJUNE  ATLE NESJE 《Boreas: An International Journal of Quaternary Research》2010,39(4):649-654

Seppä, H., Birks, H. J. B., Bjune, A. E. & Nesje, A. 2010: Current continental palaeoclimatic research in the Nordic region (100 years since Gunnar Andersson 1909) – Introduction. Boreas, Vol. 39, pp. 649‐654. 10.1111/j.1502‐3885.2010.00170.x. ISSN 0300‐9483.  相似文献   

Water vapour ¹⁸O/¹⁶O isotope ratio in surface air in New England, USA     

XUHUI LEE  RONALD SMITH  JOHN WILLIAMS 《Tellus. Series B, Chemical and physical meteorology》2006,58(4):293-304

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A geological tourist in Kenya     

JOHN C. THACKRAY 《Geology Today》1991,7(1):29-31

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The late Miocene to Pleistocene ice-rafting history of southeast Greenland     

KRISTEN E. K. ST. JOHN  LAWRENCE A. KRISSEK 《Boreas: An International Journal of Quaternary Research》2002,31(1):28-35

Analysis of a Miocene-Pleistocene ice-rafted debris (IRD) record from the western Irminger Basin provides evidence for the initiation and long-term behavior of the SE portion of the Greenland Ice Sheet. In the late Miocene (~7.3 Ma), IRD supply to Ocean Drilling Program site 918 increased significantly indicating that glaciers large enough to reach sea level were present in SE Greenland long before the onset of widespread Northern Hemisphere glaciation. IRD accumulated at this site throughout the Pliocene and Pleistocene, supporting the hypothesis that SE Greenland was a key nucleation area for the formation of the Greenland Ice Sheet. Since glacial onset, the western Irminger Basin IRD record is characterized by a succession of episodes with high IRD mass accumulation rates (MARs). The site 918 IRD record indicates that greatest iceberg production in SE Greenland occurred during major climatic transitions (e.g. widespread Northern Hemisphere glacial expansion at 2.7 Ma and the mid-Pleistocene climate shift at 0.9 Ma), and that SE Greenland sometimes also led the northern North Atlantic region in glacial response to climatic forcing (e.g. glacial intensification at ~4.8 and, along with NE Greenland, at ~3.5 Ma).  相似文献   

Morphology, geology and oceanography of the Hinlopen Strait and Trough, Svalbard, Norway     

STEPHANIE PFIRMAN  JOHN D. MILLIMAN 《Polar research》1987,5(3):297-298

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Minor end moraines of the Wisconsin Valley Lobe, north-central Wisconsin, USA     

NELSON R. HAM  JOHN W. ATTIG 《Boreas: An International Journal of Quaternary Research》2001,30(1):31-41

Approximately 35 parallel, discontinuous glacial ridges occur in an area of about 100 km² in north‐central Wisconsin. The ridges are located between about 6 and 15 km north (formerly up‐ice) of the maximum extent of the Wisconsin Valley Lobe of the Laurentide Ice Sheet. The ridges are between 1 and 4 m high, up to 1 km long, and spaced between 30 and 80 m apart. They are typically asymmetrical with a steep proximal (ice‐contact) slope and gentle distal slope. The ridges are composed primarily of subglacial till on their proximal sides and glacial debris‐flow sediment on the distal sides. In some ridges the till and debris‐flow sediment are underlain by sorted sediment that was deformed in the former direction of ice flow. We interpret the ridges to be recessional moraines that formed as the Wisconsin Valley Lobe wasted back from its maximum extent, with each ridge having formed by a sequence of (1) pushing of sorted ice‐marginal sediment, (2) partial overriding by the glacier and deposition of subglacial till on the proximal side of the ridge, and (3) deposition of debris‐flow sediment on the distal side of the ridge after the frozen till at the crest of the ridge melted. The moraines are similar to annual recessional moraines described at several modern glaciers, especially the northern margin of Myrdalsjokull, Iceland. Thus, we believe the ridges probably formed as a result of minor winter advances of the ice margin during deglaciation. Based on this assumption, we calculate the net rate of ice‐surface lowering of the Wisconsin Valley Lobe during the period when the moraines formed. Various estimates of ice‐surface slope and rates of ice‐margin retreat yield a wide range of values for ice‐surface lowering (1.7–14.5 m/yr). Given that ablation rates must exceed those of ice‐surface lowering, this range of values suggests relatively high summer temperatures along the margin of the Wisconsin Valley Lobe when it began retreating from its maximum extent. In addition, the formation of annual moraines indicates that the glacier toe was thin, the ice surface was clean, and the ice margin experienced relatively cold winters.  相似文献   

Terrigenous sand in Labrador Sea hemipelagic sediments and paleoglacial events on Baffin Island over the last 100,00 years     

RICHARD H. FILLON  GIFFORD H. MILLER  JOHN T. ANDREWS 《Boreas: An International Journal of Quaternary Research》1981,10(1):107-124

Eight Labrador Sea piston cores with faunal and ash-zone stratigraphies correlated to deep-sea oxygen isotope stages were used to compute Labrador Sea terrigenous sand input rates (mg/cm²/1000 years) during the last 100,000 years. Sources of the sand in Labrador Sea cores are likely to be ice-rafting, turbid glacial meltwater inflow or deflation and wind erosion of unvegetated landscapes in the wake of retreating continental ice sheets. High levels of sand input to the Labrador Sea are therefore undoubtedly glacier-related while low levels of sand input are not. Comparison of the history of Labrador Sea sand input with the chronology of glacial and non-glacial events on Baffin Island reveals that the era of highest sand input rates, the isotopic stage 5a/4 transition, closely coincided with an episode of early Foxe glacier advance to tidewater (Ayr Lake Stade) along the outer coast of Baffin Island ca. 80,000 B.P. to 60,000 B.P. The period of lowest Labrador Sea sand input rates, late isotopic stage 3 to the present, largely corresponds to a major disconformity in the raised marine and glacigenic sediments on Baffin Island, but includes also the late Foxe/early Holocene Cockburn glacial advance (which did not reach the outer coast of the island) and the modern glacial minimum. Labrador Sea and central-subpolar North Atlantic sand input histories are reciprocally related over the last 80,000 years. Accelerated sand input in the Labrador Sea during times of reduced sand input in the North Atlantic implies: (1) major early Wisconsin glacier expansion in the circum Labrador Sea/Baffin Bay region and/or; (2) a surface circulation pattern in the North Atlantic which inhibited iceberg melting there while delivering icebergs and relatively warm surface water into the Labrador Sea. Conversely, reduced sand input in the Labrador Sea during times of accelerated sand input in the North Atlantic implies: (1) late Wisconsin glacier recession in the circum Labrador Sea/Baffin Bay region and/or; (2) a circulation pattern which carries icebergs southward and eastward away from the Labrador Sea. These implications are discussed in the light of paleoceanographic evidence for three periods - 80,000 B.P. to 57,000 B.P.; 25,000 B.P. to 13,000 B.P.; and 13,000 B.P. to 9800 B.P  相似文献   

Mid-Jurassic through mid-Cretaceous extension in the Central Graben of the North Sea - part 1: estimates from subsidence     

STEVEN J. Hellinger  JOHN G. Sclater  JOHN Giltner† 《Basin Research》1988,1(4):191-200

Abstract The post early Carboniferous subsidence history of the Central North Sea basin can be separated into three major periods: Permian, Triassic and post Mid-Jurassic. Prior efforts to account for this subsidence within an extensional framework have concentrated on the post Mid-Jurassic. These efforts have assumed that the effects of the previous periods of extension necessary to create the Permian and Triassic subsidence are negligible. We consider the 80-km value for the Mid-Jurassic-mid-Cretaceous extension from these efforts a reasonable upper estimate of the likely amount of extension. This value has received considerable criticism as it is almost four times as great as that determined by summing the horizontal displacement (heave) on faults observed on industry seismic lines in the area.
We treat the two earlier phases of extension as one phase and develop a method to estimate the maximum value of this extension. We use this value, with estimates of the total extension from the early Carboniferous to Present, to determine a likely minimum value for the mid-Mid-Jurassic through mid-Cretaceous extension. After justifying the use of Airy isostasy for the loading response of the lithosphere we show that the observed unloaded basement subsidence history is compatible with the parameters we derive for the pre and post Mid-Jurassic extension. Our minimum estimate of 38 km is still significantly higher than that: made by summing the heave on the faults active throughout the Upper Jurassic and lower Cretaceous.  相似文献