Are continental glaciations induced by orogeny? Evidence from major element geochemistry of Cenozoic muds and ancient glacial deposits

Author(s): Young, Grant M.; Nesbitt, H. Wayne
Author Affiliation(s): Primary:
University of Western Ontario, Department of Earth Sciences, London, ON, Canada
Volume Title: Geological Society of America, 28th annual meeting
Source: Abstracts with Programs - Geological Society of America, 28(7), p.505; Geological Society of America, 28th annual meeting, Denver, CO, Oct. 28-31, 1996. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: Mountain uplift and glaciation in low latitudes may have played a significant role in deterioration of global climate over the last 40Ma. Upward-increasing Sr ratios in marine carbonates are thought to reflect increased silicate weathering, attributed to comminution of minerals during transport in mountain glaciers and subsequent fluvial transport to lower altitudes. To further investigate this question, a Chemical Index of Alteration (CIA), which provides a proxy for silicate weathering, was calculated for samples of Cenozoic siliciclastic muds from DSDP drill sites in both low (Sites 146,149) and high latitudes (Site 328). The low latitude samples show clear evidence of upward-increasing weathering during the last 40 Ma. Samples from Site 328, by contrast, show upward-decreasing values (decreasing weathering) that correspond closely to existing oxygen isotope data and other evidence of Cenozoic climatic deterioration. These results provide strong evidence that (orogenically-induced?) increases in low latitude weathering occurred at the same time as global climatic cooling and development of continental glaciers in high latitudes. Widespread preservation and the unweathered nature of materials (low CIA values) in many ancient glacial deposits such as the Paleoproterozoic Gowganda Formation indicate that they formed under conditions comparable to those of Recent low latitude continental glaciers. By analogy with the Cenozoic, such Proterozoic glaciations may have formed in response to cryptic, orogenically-induced (end-Archean, Pan African) mountain glaciations. Deposits formed as a result of such alpine glaciations in low latitudes would be physically and chemically unrecognizeable in the geological record because the glaciogenic materials would be reworked by fluvial systems and would undergo chemical weathering at low altitudes.
Year of Publication: 1996
Research Program: DSDP Deep Sea Drilling Project
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 16 Structural Geology; Ancient ice ages; Atlantic Ocean; Canada; Caribbean Sea; Cenozoic; Chemical weathering; Clastic sediments; Cooling; DSDP Site 146; DSDP Site 149; DSDP Site 328; Deep Sea Drilling Project; Eastern Canada; Geochemistry; Glacial geology; Glaciation; Gowganda Formation; Huronian; Leg 15; Leg 36; Major elements; Mud; Neogene; North Atlantic; Oligocene; Ontario; Orogeny; Paleoclimatology; Paleogene; Pan-African Orogeny; Precambrian; Proterozoic; Sediments; South Atlantic; Tertiary; Uplifts; Upper Precambrian; Weathering
Coordinates: N150659 N150659 W0692240 W0692240
N150615 N150615 W0692151 W0692151
S494841 S494840 W0363931 W0363932
Record ID: 1997039965
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States