Evaluation of Carbonate Platform Records to Track Greenhouse, Transitional and Icehouse Worlds through the Paleozoic

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Evaluation of Carbonate Platform Records to Track Greenhouse, Transitional and Icehouse Worlds through the Paleozoic J. F. Read Virginia Polytechnic Institute and State University ERA-0341753 ABSTRACT Shallow marine carbonate shelves act as dipsticks to global sea level changes driven in part by climate and global ice volume. Thus we propose to use them to reconstruct sea level history during their growth using a combination of field studies, literature search, and computer modeling. This will provide insight into global ice volume and climate changes from 550 to 250 million years ago, at higher resolution than has been attempted previously. Carbonate platforms record relatively high frequency climate changes driven by the earths orbit that leave a distinctive signature in the rock record depending on the earth's global climate at the time. During greenhouse times, carbonate platforms develop under the influence of many small (few meter) sea level changes driven by precession (roughly 15 to 20 thousand year periods). When the earth has abundant ice at the poles, sea level changes may be large (up to 100 m or more) and tend to be driven by obliquity and eccentricity (roughly 40 thousand, 100 to 400 thousand year periods). Between these two end members, when the earth contained moderate amounts of global ice, sea level changes likely were a few tens of meters or less. Such transitional states appear to occupy a significant amount of the geological record, and have been overlooked in the past. In addition, many of the giant oil fields in carbonate rocks appear to have formed under such transitional climatic states. The study will thus provide a long term window into global climate change. It will also clarify how global climate has influenced the geological distribution of carbonate reservoirs hosting giant petroleum fields.