scholarly journals Evolution and diversification of the Southern Chilean genus Ceroglossus (Coleoptera, Carabidae) during the Pleistocene glaciations

2021 ◽  
Author(s):  
Alejandro López‐López ◽  
Víctor Acosta ◽  
Laurent Rataj ◽  
José Galián
Keyword(s):  
Pleistocene Glaciations

scholarly journals High-resolution seismic reflection profiling: an aid for resolving the Pleistocene stratigraphy of a buried valley in central Illinois, USA

2013 ◽  
Vol 54 (64) ◽  
pp. 10-20 ◽  
Author(s):  
Andrew J. Stumpf ◽  
Ahmed Ismail
Keyword(s):  
High Resolution ◽  
Seismic Reflection ◽  
Pleistocene Glaciations ◽  
Glacial Sediments ◽  
Borehole Geophysics ◽  
Valley Fill ◽  
Sedimentary Sequences ◽  
Valley Fills ◽  
Central Illinois ◽  
Sand And Gravel

Abstract High-resolution seismic reflection (HRSR) data acquired over the Pesotum Bedrock Valley in central Illinois, USA, helped construct the seismic stratigraphy of a valley fill and the overlying sediments. Integrating these data with drilling and borehole geophysics allowed us to develop a seismo-stratigraphic classification for sediments on undulating and folded bedrock. Seven seismo-stratigraphic units that overlie the bedrock surface were characterized. Seismic units A and B include glacial sediments of multiple Pleistocene glaciations above the Pesotum Bedrock Valley, which completely mask the feature. Seismic units C–F, the valley fill, primarily include tills and glacial lake sediment deposited during the earliest Pleistocene glaciations and preglacial alluvium and colluvium that is draped over in situ weathered bedrock. The preservation of conformable-lying glacial and preglacial deposits and paucity of sand and gravel in the buried valley strongly indicate that little or no incision by glacial meltwaters has occurred. These observations contrast markedly with interpretations from buried valleys elsewhere in North America and northern Europe where valley fills contain significant deposits of sand and gravel in tunnel valleys. The HRSR data assisted the characterization and analysis of heterogeneous sedimentary sequences over a buried valley where existing subsurface information was limited. The extent of Pleistocene-age glacial lakes is inferred from the lateral continuity of silt and clay units.

Dating Early and Middle (Reid) Pleistocene Glaciations in Central Yukon by Tephrochronology

2001 ◽  
Vol 56 (3) ◽  
pp. 335-348 ◽  
Author(s):  
John A. Westgate ◽  
Shari J. Preece ◽  
Duane G. Froese ◽  
Robert C. Walter ◽  
Amanjit S. Sandhu ◽  
...  
Keyword(s):  
Gulf Of Alaska ◽  
Supporting Evidence ◽  
Pleistocene Glaciations ◽  
Late Cenozoic ◽  
Aeolian Sand ◽  
Oxygen Isotope Stage ◽  
Aleutian Arc ◽  
Dawson City ◽  
Cordilleran Ice Sheet ◽  
Tephra Beds

AbstractThe late Cenozoic deposits of central Yukon contain numerous distal tephra beds, derived from vents in the Wrangell Mountains and Aleutian arc–Alaska Peninsula region. We use a few of these tephra beds to gain a better understanding on the timing of extensive Pleistocene glaciations that affected this area. Exposures at Fort Selkirk show that the Cordilleran Ice Sheet advanced close to the outer limit of glaciation about 1.5 myr ago. At the Midnight Dome Terrace, near Dawson City, exposed outwash gravel, aeolian sand, and loess, related to valley glaciers in the adjacent Ogilvie Mountains, are of the same age. Reid glacial deposits at Ash Bend on the Stewart River are older than oxygen isotope stage (OIS) 6 and likely of OIS 8 age, that is, about 250,000 yr B.P. Supporting evidence for this chronology comes from major peaks in the rates of terrigeneous sediment input into the Gulf of Alaska at 1.5 and 0.25 myr B.P.

Paleomagnetic evidence for late Cenozoic glaciations in the Mackenzie Mountains of the Northwest Territories, Canada

1996 ◽  
Vol 33 (6) ◽  
pp. 896-903 ◽  
Author(s):  
R. W. Barendregt ◽  
R. J. Enkin ◽  
J. Baker ◽  
A. Duk-Rodkin
Keyword(s):  
Large Scale ◽  
Magnetic Measurements ◽  
Laurentide Ice Sheet ◽  
Paleoenvironmental Reconstruction ◽  
Pleistocene Glaciations ◽  
Late Cenozoic ◽  
Last Glaciation ◽  
Stratigraphic Record ◽  
Bear River ◽  
Mackenzie Mountains

The Mackenzie Mountains were affected by montane valley glaciers during the Pleistocene and peripherally by the Laurentide Ice Sheet during the last glaciation. In this paper we report on magnetostratigraphic dating and correlation of three sections recording Late Pliocene to Late Pleistocene glaciations: Katherine Creek, Little Bear River, and Inlin Brook (located around 65°N, 127°W). Each section consists of a colluvial unit overlying a Pliocene pediment surface cut into Proterozoic or Paleozoic bedrock, or Tertiary gravel, which is in turn overlain by a stack of five, and in places six, montane tills, usually with soils developed at their surfaces, and capped by a Laurentide till. Normal and reversed magnetizations were recognized with single-domain magnetite as a dominant remanence carrier. The Katherine Creek section has a normally magnetized colluvium at its base, which is overlain by two reversed tills, succeeded by three normal tills. We interpret the top two tills to be of Brunhes age (< 780 ka) but argue that the lowermost normal till is of probable Olduvai age (ca. 1.8 Ma). The two underlying tills are of Matuyama age (2.6 Ma to 780 ka), and the colluvial base is assigned to the Gauss (3.5–2.6 Ma). The Little Bear River section exposes a stratigraphic record similar to that found at Katherine Creek. Only four units could be assigned a paleomagnetic polarity, the others yielding incoherent results. Paleosols on the first and second till units were reversed and normal, respectively, and the top till was normal. Thus there is clear evidence of an older (reversed) Pleistocene glaciation and a magnetostratigraphic record compatible with that found at Katherine Creek. Magnetic measurements from Inlin Brook gave largely incoherent results, with the exception of the surface (Laurentide) till, which is normal. The glacial history recorded in the Mackenzie Mountains correlates well with other studies carried out in the Cordillera. The large-scale changes in climate revealed in these terrestrial records provide baseline data for paleoenvironmental reconstruction.

scholarly journals The Pleistocene Glaciations of the North Sea Basin

2011 ◽  
pp. 261-278 ◽  
Author(s):  
Alastair G.C. Graham ◽  
Martyn S. Stoker ◽  
Lidia Lonergan ◽  
Tom Bradwell ◽  
Margaret A. Stewart
Keyword(s):  
North Sea ◽  
Pleistocene Glaciations ◽  
The North ◽  
The North Sea
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