Post-Glacial Fossil Mollusca in Western Canada

1934 ◽  
Vol 71 (8) ◽  
pp. 370-382 ◽  
Author(s):  
Alan Mozley
Keyword(s):  
Ice Sheets ◽  
Field Work ◽  
General Nature ◽  
Western Canada ◽  
Glacial Retreat ◽  
Last Glacial Period ◽  
History Of ◽  
Molluscan Fauna ◽  
Made In ◽  
The Last Glacial

From the standpoint of biological geography, the most significant event in the recent history of Canada has been the occurrence of widespread severe glaciation. This resulted in the whole of the previously existing fauna being either exterminated or driven southward. When the ice sheets receded northwards at the end of the last glacial period, this region was once more populated by animals, including both fresh water and terrestrial mollusca, the remains of which are to be found in various post-glacial deposits. The migration of animals into this new territory did not take place all at once, and it is noteworthy that no fossil mollusca have been found in the deposits laid down during the early stages of the glacial retreat. The purpose of this paper is to give in concise form the history of the present molluscan fauna of this region in so far as it is evidenced by the post-glacial fossils found in the region. The series of fossil-bearing deposits herein described is far from complete, and many additional finds will doubtless be made in the course offuture field work. Nevertheless, a sufficient number of observations has been made to indicate the general nature and duration of the molluscan immigration into the area.

scholarly journals Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 55-60
Author(s):  
Anja L.L.M. Verbers ◽  
Volkmar Damm
Keyword(s):  
Ice Sheet ◽  
Field Work ◽  
Topographic Map ◽  
Glacial History ◽  
Ice Surface ◽  
Victoria Land ◽  
Radio Echo Sounding ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.

Archaeology in New China

Antiquity ◽  
1963 ◽  
Vol 37 (147) ◽  
pp. 176-184 ◽  
Author(s):  
Hsia Nai
Keyword(s):  
Field Work ◽  
Archaeological Research ◽  
Historical Science ◽  
Considerable Success ◽  
Large Numbers ◽  
History Of ◽  
Ancient Monuments ◽  
Economic Construction ◽  
Abundant Data ◽  
Made In

Archaeology as a branch of historical science has made new headway in the thirteen years since the founding of the Chinese People's Republic. The scale of its work has expanded and methods of research have been improved. Large numbers of young archaeological workers have been trained. In the course of the nation's gigantic economic construction, remains of ancient settlements and tombs have been uncovered in many places, yielding numerous important relics which have provided abundant data for archaeological research. Throughout the country, hosts of archaeological workers from research institutes, universities, museums and institutions for the preservation of ancient monuments are carrying out both field work and academic study and have already attained considerable success in their efforts to explore the history of ancient China on the basis of archaeological finds. All this has given further impetus to the advance of Chinese archaeology.Archaeological finds made in New China are so rich that the present article can attempt to discuss only some of the most important problems.

scholarly journals Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 55-60
Author(s):  
Anja L.L.M. Verbers ◽  
Volkmar Damm
Keyword(s):  
Ice Sheet ◽  
Field Work ◽  
Topographic Map ◽  
Glacial History ◽  
Ice Surface ◽  
Victoria Land ◽  
Radio Echo Sounding ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.

scholarly journals Palaeogeographical And Archaeological Records Of Natural Changes Of The Jordanowo-Niesulice Subglacial Channel Near Lubrza, The Lubusz Lakeland

2015 ◽  
Vol 34 (3) ◽  
pp. 101-116 ◽  
Author(s):  
Magdalena Ratajczak-Szczerba ◽  
Iwona Sobkowiak-Tabaka ◽  
Iwona Okuniewska-Nowaczyk
Keyword(s):  
Late Glacial ◽  
Last Glacial Period ◽  
Geochemical Composition ◽  
Palynological Analysis ◽  
The Holocene ◽  
Ams Radiocarbon Dating ◽  
History Of ◽  
Geomorphological Analysis ◽  
Geological Research ◽  
The Last Glacial

Abstract The region of the Lubusz Lakeland in western Poland where there are a lot of subglacial channels provides opportunity for multi-proxy palaeoenvironmental reconstructions. None of them has not been the object of a specific study. The developmental history of the palaeolakes and their vicinity in the subglacial trough Jordanowo-Niesulice, spanning the Late Glacial and beginning of the Holocene, was investigated using geological research, lithological and geomorphological analysis, geochemical composition, palynological and archaeological research, OSL and AMS-radiocarbon dating. Geological research shows varied morphology of subglacial channel where at least two different reservoirs functioned in the end of the Last Glacial period and at the beginning of the Holocene. Mostly during the Bølling-Allerød interval and at the beginning of the Younger Dryas there took place melting of buried ice-blocks which preserved the analysied course of the Jordanowo-Niesulice trough. The level of water, and especially depth of reservoirs underwent also changes. Palynological analysis shows very diversified course of the Allerød interval.

Pleistocene history of Betula with special reference to the British Isles

1984 ◽  
Vol 85 (1-2) ◽  
pp. 1-11 ◽  
Author(s):  
J. H. Dickson
Keyword(s):  
Special Reference ◽  
Glacial Period ◽  
British Isles ◽  
Last Glacial Period ◽  
Glacial Sediments ◽  
Last Glacial ◽  
History Of ◽  
The Last Glacial

SynopsisBetula is well represented in the Pleistocene deposits of the British Isles; B. nana is often recovered from glacial sediments and tree Betula flourished early and late in the interglacial periods. In western and northern Britain, tree Betula has remained important in the forests since the last glacial period.

scholarly journals Oceanic forcing of the Eurasian Ice Sheet on millennial time scales during the Last Glacial Period

2018 ◽  
Author(s):  
Jorge Alvarez-Solas ◽  
Rubén Banderas ◽  
Alexander Robinson ◽  
Marisa Montoya
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
Climate Changes ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. The last glacial period (LGP; ca.110–10 ka BP) was marked by the existence of two types of abrupt climatic changes, Dansgaard-Oeschger (DO) and Heinrich (H) events. Although the mechanisms behind these are not fully understood, it is generally accepted that the presence of ice sheets played an important role in their occurrence. While an important effort has been made to investigate the dynamics and evolution of the Laurentide Ice Sheet (LIS) during this period, the Eurasian Ice Sheet (EIS) has not received much attention, in particular from a modeling perspective. However, meltwater discharge from this and other ice sheets surrounding the Nordic Seas is often implied as a potential cause of ocean instabilities that lead to glacial abrupt climate changes. Thus, a better understanding of its variations during the LGP is important to understand its role in glacial abrupt climate changes. Here we investigate the response of the EIS to millennial-scale climate variability during the LGP. We use a hybrid, three-dimensional, thermomechanical ice-sheet model that includes ice shelves and ice streams. The model is forced offline through a novel perturbative approach that includes the effect of both atmospheric and oceanic variations and provides a more realistic treatment of millennial-scale climatic variability than conventional methods. Our results show that the EIS responds with enhanced ice discharge in phase with interstadial warming in the North Atlantic when forced with surface ocean temperatures. Conversely, when subsurface ocean temperatures are used, enhanced ice discharge occurs both during stadials and at the beginning of the interstadials. Separating the atmospheric and oceanic effects demonstrates the major role of the ocean in controlling the dynamics of the EIS on millennial time scales. While the atmospheric forcing alone is only able to produce modest iceberg discharges, warming of the ocean leads to higher rates of iceberg discharges as a result of relatively strong basal melting at the margins of the ice sheet. Together with previous work, our results provide a consistent explanation for the response of the LIS and the EIS to glacial abrupt climate changes, and highlight the need for stronger constraints on the local North Atlantic behavior in order to improve our understanding of the ice sheet's glacial dynamics.

scholarly journals Calving Ice Walls

1989 ◽  
Vol 12 ◽  
pp. 74-80 ◽  
Author(s):  
T. Hughes
Keyword(s):  
Shear Bands ◽  
Ice Sheets ◽  
Field Work ◽  
Field Studies ◽  
Line Field ◽  
Dry Land ◽  
Water Trough ◽  
Ablation Mechanism ◽  
Shear Rupture ◽  
Made In

Calving ice walls are an important ablation mechanism for deglaciation of calving bays occupied by temperate tide-water glaciers and polar marine ice sheets. Dangers inherent in calving bays have precluded detailed field studies of these calving ice walls. However, calving ice walls also exist in sub-polar glaciers terminating on dry land, and an opportunity for detailed field work was afforded by the 12 August 1970 volcanic eruption on Deception Island (63.0°S, 60.6°W), where thawing of a surface blanket of ice-cemented ash produced solifluction ramps that made parts of the ice wall accessible. Measurements made in a melt-water trough incised into the ice wall, and in four tunnels cut into the ice wall, revealed numerous shear bands that rose almost vertically and curved forward. Shear offset increased upward and was greatest in shear bands that intersected the tips of ring-fault crevasses on the up-slope side of the ice wall. Near the base of the ice wall, other shear bands, possibly related to the slip-line field, intersected the ice wall at about 45°. Ice slabs separated by ring faults calved straight down as a result of shear rupture along these two sets of shear bands. Calving dynamics were analyzed and generalized for ice walls grounded in water.

scholarly journals Millennial and sub-millennial scale climatic variations recorded in polar ice cores over the last glacial period

2010 ◽  
Vol 6 (1) ◽  
pp. 135-183 ◽  
Author(s):  
E. Capron ◽  
A. Landais ◽  
J. Chappellaz ◽  
A. Schilt ◽  
D. Buiron ◽  
...  
Keyword(s):  
Climatic Variability ◽  
Ice Sheets ◽  
Ice Cores ◽  
Glacial Period ◽  
Last Glacial Period ◽  
Last Glacial ◽  
Dronning Maud Land ◽  
Mis 5 ◽  
The Last Glacial ◽  
Millennial Scale

Abstract. Since its discovery in Greenland ice cores, the millennial scale climatic variability of the last glacial period has been increasingly documented at all latitudes with studies focusing mainly on Marine Isotopic Stage 3 (MIS 3; 28–60 thousand of years before present, hereafter ka) and characterized by short Dansgaard-Oeschger (DO) events. Recent and new results obtained on the EPICA and NorthGRIP ice cores now precisely describe the rapid variations of Antarctic and Greenland temperature during MIS 5 (73.5–123 ka), a time period corresponding to relatively high sea level. The results display a succession of long DO events enabling us to highlight a sub-millennial scale climatic variability depicted by i) short-lived and abrupt warming events preceding some Greenland InterStadial (GIS) (precursor-type events) and ii) abrupt warming events at the end of some GIS (rebound-type events). The occurrence of these secondary events is suggested to be driven by the Northern Hemisphere summertime insolation at 65° N together with the internal forcing of ice sheets. Thanks to a recent NorthGRIP-EPICA Dronning Maud Land (EDML) common timescale over MIS 5, the bipolar sequence of climatic events can be established at millennial to sub-millennial timescale. This provides evidence that a linear relationship is not satisfactory in explaining the link between Antarctic warming amplitudes and the duration of their concurrent Greenland Stadial (GS) for the entire glacial period. The conceptual model for a thermal bipolar seesaw permits a reconstruction of the Antarctic response to the northern millennial and sub-millennial scale variability over MIS 5. However, we show that when ice sheets are extensive, Antarctica does not necessarily warm during the whole GS as the thermal bipolar seesaw model would predict.

scholarly journals Evaluation of 14C Ages of Organic Fractions of Paleosols from Loess-Paleosol Sequences Near Xian, China

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 680-695 ◽  
Author(s):  
M J Head ◽  
Weijian Zhou ◽  
Mingfu Zhou
Keyword(s):  
Shaanxi Province ◽  
Agricultural Activity ◽  
Agricultural Activities ◽  
The Loess Plateau ◽  
Last Glacial Period ◽  
Period Analysis ◽  
History Of ◽  
Climatic History ◽  
Organic Fractions ◽  
The Last Glacial

The 14C dating of organic fractions from paleosol layers containing &lt;2% carbon in loess-paleosol sequences from the loess plateau in China has yielded results that are quite often much younger than the true age of the sediments. Percolation of modern organic materials from agricultural activities, and binding of these materials within the weathered clays of the paleosols has meant that conventional pretreatment techniques for 14C dating would not isolate a reliable chemical fraction. The total sequence from Bei Zhuang Cun, in Shaanxi Province, reflects the climatic history of the area for ca 30,000 years, ranging from the interstadial of the last glacial period to the postglacial period. Analysis of solvent extracts of organic material from this site indicates that they are mainly composed of carbohydrate residues originating from the relatively recent agricultural activity. Validity of the humic components for dating will be discussed.

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