A Late Ordovician ice sheet in South America: Evidence from the Cancañiri tillites, southern Bolivia

2007 ◽  
Author(s):  
Frank Schönian ◽  
Sven O. Egenhoff
Keyword(s):  
South America ◽  
Ice Sheet ◽  
Late Ordovician

scholarly journals Red Sea tectonics unveil the largest known terrestrial ice stream: New constraints on Late Ordovician ice sheet dynamics

2021 ◽  
Author(s):  
Mohamed Elhebiry ◽  
Mohamed Sultan ◽  
Abotalib Abotalib ◽  
Alan Kehew ◽  
Peter Voice ◽  
...  
Keyword(s):  
Red Sea ◽  
Climate Models ◽  
Ice Sheet ◽  
Late Ordovician ◽  
Ice Streams ◽  
Glacial Origin ◽  
Tectonic Processes ◽  
Ice Stream ◽  
Aeolian Erosion ◽  
Ice Sheet Dynamics

Abstract Mega-streamlined landforms on Earth and Mars have been attributed to aeolian, glaciogenic, fluvial, and tectonic processes. Identifying the forces that shaped these landforms is paramount for understanding landscape evolution and constraining paleo-climate models and ice sheet reconstructions. In Arabia, east-northeast, kilometer-scale streamlined landforms were interpreted to have been formed by Quaternary aeolian erosion. We provide field and satellite-based evidence for a Late Ordovician glacial origin for these streamlined landforms, which were exhumed during the Red Sea–related uplift. Then we use Late Ordovician paleo-topographic data to reconstruct the Late Ordovician ice sheet using identified and previously reported glacial deposits and landforms. Our reconstruction suggests these glacial features are part of a major, topographically controlled, marine-terminating ice stream, twice the length of the largest known terrestrial ice streams. Our results support models that advocate for a single, major, and highly dynamic ice sheet and provide new morphological-based constraints for Late Ordovician climate models.

Did the Late Ordovician African ice sheet reach Europe?

Geology ◽  
2010 ◽  
Vol 38 (3) ◽  
pp. 279-282 ◽  
Author(s):  
Juan C. Gutiérrez-Marco ◽  
Jean-François Ghienne ◽  
Enrique Bernárdez ◽  
Manuel P. Hacar
Keyword(s):  
Ice Sheet ◽  
Late Ordovician

A sea-level fingerprint of the Late Ordovician ice-sheet collapse

Geology ◽  
2018 ◽  
Vol 46 (7) ◽  
pp. 595-598 ◽  
Author(s):  
A. Pohl ◽  
J. Austermann
Keyword(s):  
Sea Level ◽  
Ice Sheet ◽  
Late Ordovician

Paleolongitudinal estimates for paleocontinents derived from interplate distances based on Late Ordovician bivalves

Paleobiology ◽  
2011 ◽  
Vol 37 (3) ◽  
pp. 438-444 ◽  
Author(s):  
William F. Schmachtenberg
Keyword(s):  
Regression Analysis ◽  
South America ◽  
Least Squares ◽  
Late Ordovician ◽  
Similarity Analysis ◽  
Least Squares Regression ◽  
Dice Coefficient ◽  
The Past ◽  
Paleoclimatic Data ◽  
Faunal Similarity

The geographic distribution of 293 Modern bivalve genera has been analyzed and found to be statistically correlated with distance. In particular, a least-squares regression analysis of the data indicates that the distance between faunal realms (D) in kilometers can be estimated using the equation D = (ln(d) + 0.4233)/−0.00013, where d is the Dice coefficient of faunal similarity. Analysis of 59 genera of Late Ordovician bivalves indicates that the above equation also describes their biogeographic distribution.Using this formula, the distance between Laurentia and Scotland/Northwest Ireland was estimated to be 5500 kilometers. This is consistent with the reconstruction of a connection among these areas during the Late Ordovician based on brachiopod and graptolite biogeographic data.Paleomagnetic and paleoclimatic data also suggest that Avalonia, Baltica, and Laurentia were at tropical latitudes. Distances between these paleocontinents can therefore be used to estimate paleolongitudes. If the location of England on the eastern side of Avalonia is used as zero degrees paleolongitude for the Late Ordovician as it is today, the paleolongitude for South America, Laurentia, Scotland and northwest Ireland, and Baltica would be 125°W, 45°W, 10°W, and 15°E, respectively. Because of drifting of the Avalonia plate, these paleolongitudes probably do not coincide with the longitudinal grid used today. The paleolongitudes indicate only the relative spacing between continents in the past. The methodology in this study should be useful for improving the accuracy of paleogeographic reconstructions for the Late Ordovician throughout the Cenozoic, and especially the Paleozoic periods for which magnetic seafloor anomaly data are not available.

The development of an atypical Hirnantia-brachiopod Fauna and the onset of glaciation in the late Ordovician of Gondwana

2001 ◽  
Vol 92 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Owen E. Sutcliffe ◽  
David A. T. Harper ◽  
Abdallah Aït Salem ◽  
Robert J. Whittington ◽  
Jonathan Craig
Keyword(s):  
Continental Shelf ◽  
Sea Level ◽  
North Africa ◽  
Mass Extinction ◽  
Ice Sheet ◽  
Late Ordovician ◽  
Shallow Marine ◽  
Marine Deposits ◽  
Brachiopod Fauna ◽  
Glaciomarine Sediments

ABSTRACTThe development of an atypical Hirnantia Fauna in the late Ordovician of Gondwana was coeval with a slow eustatic fall induced by the abstraction of water into a growing ice sheet. This event is dated as early Hirnantian in age and occurred in tandem with the start of a major mass extinction. A tectonic episode in the Caradoc-Ashgill of North Africa differentiated the continental shelf into highs and lows and may have formed the land required for the accumulation of a permanent snow cover. Depositional lows were filled by regressive shallow-marine deposits in the early Hirnantian. During the mid-Hirnantian, advance and retreat of an ice sheet on the continental shelf resulted in the deposition of glaciomarine sediments above these regressive deposits. The demise of an atypical Hirnantia Fauna is attributed to deglaciation and the associated flooding of the continental shelf by a stratified anoxic water column. This glacioeustatic sea-level rise occurred in the late Hirnantian.

First-order reconstructions of a Late Ordovician Saharan ice sheet

2008 ◽  
Vol 165 (1) ◽  
pp. 19-29 ◽  
Author(s):  
D.P. Le Heron ◽  
J. Craig
Keyword(s):  
Ice Sheet ◽  
Late Ordovician ◽  
First Order
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