| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | February 13, 2009 |
| Latest Amendment Date: | January 14, 2010 |
| Award Number: | 0842946 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Lisa Boush
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | April 1, 2009 |
| End Date: | March 31, 2013 (Estimated) |
| Total Intended Award Amount: | $202,999.00 |
| Total Awarded Amount to Date: | $202,999.00 |
| Funds Obligated to Date: |
FY 2010 = $102,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
1 NASSAU HALL PRINCETON NJ US 08544-2001 (609)258-3090 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
1 NASSAU HALL PRINCETON NJ US 08544-2001 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Sedimentary Geo & Paleobiology |
| Primary Program Source: |
01001011DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Fluctuating Tidewater Glaciers, Chemical Weathering and Survival of
Reef-Dwelling Organisms: the Marinoan Snowball, South Australia
Adam Maloof
Princeton University
The snowball Earth hypothesis posits that the oceans were sealed in ice for millions of years, at least once or twice, between 720 and 635 million years ago. However, three observations have caused some to question this backbone of the snowball Earth hypothesis: (1) There is geological evidence for dynamic wet-based glaciers, in the form of thick glacially derived sediments and deep glacial erosion. How was sufficient snow delivered to ice sheets to keep them flowing when the oceans were covered in ice? (2) There is geological and geochemical evidence for thermal episodicity during a single snowball interval in the form of interbedded glacial and non-glacial sediments. How would ice advance and retreat and how would variable temperature/humidity conditions develop on a deeply frozen Earth with ice-covered oceans? (3) Photosynthesizing eukaryotes appear to survive the glaciation, unscathed. How did photosynthesizers survive millions of years of freezing conditions in isolated refugia without having a major influence on the course of evolutionary biology?
The Marinoan (ended 635 Ma) glacial succession of South Australia (SA) contains the most reliable paleomagnetic evidence for equatorial sedimentation of any Neoproterozoic glacial deposit worldwide. Additionally, the Flinders and Gammons ranges of SA boast superb outcrop for hundreds of kilometers along and across paleo-shoreline strike, allowing for detailed reconstruction of sedimentary environments and lateral chemical and isotopic gradients, all in the context of 3-dimensional stratigraphy and basin analysis. With the possible exception of northern Namibia, nowhere else in the world provides such an opportunity to study the sedimentary and geochemical record of Neoproterozoic glaciation. The proposed study will document the Marinoan low-latitude glaciation in South Australia through a multidisciplinary study of the pre-, syn- and post-glacial deposits exposed in the Flinders and Gammon Ranges. Our work will evaluate the intensity of the hydrological cycle, the thermal regime of equatorial glaciers, and the evidence that multicellular life predated and survived a snowball Earth episode.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
640 million years ago, it appears that glaciers reached sea level at the equator. Such a climate state is very different than anything recorded in human history, or even during the pleistocene ice age cycles. The purpose of this project was to study the sedimentological and geochemical remains of glaciation in South Australia in order to test the "snowball Earth" hypothesis, which suggests that the entire Earth was covered in ice, including all of the oceans.
We took a unique approach in that we studied the pre-, syn-, and post-glacial sediments all at once (rather than the glacial sediments alone), to understand exactly how the region became glaciated and later deglaciated. We documented the initiation of ice cover by examining changes in the extent of rock weathering and other geochemical proxies for climate change in pre-glacial sediment. While doing so, we found evidence of perhaps the earliest animal life (sponges) growing in bacterial reefs that were then eroded by the glaciers. So animals must have survived the ensuing glaciation.
In the syn-sedimentary deposits, we found evidence of a complex landscape that recorded a single ice advance and retreat cycle charactized by near-melting temperatures. This finding means either that there was no snowball Earth, or that the sediments in South Australia only record the very end of a much longer ice age.
Finally, we documented the sedimentology and geochemistry of the rocks deposited while ice sheets melted and sea levels rose in the glacial aftermath. We were able to show that these sediments were deposited in a narrow range of water depts and recorded the changing composition and temperature of the water as post-glacial climate warmed.
Last Modified: 04/11/2013
Modified by: Adam Maloof
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