Geological Investigations of the Neogene

Paleoclimate Science

Paleoclimate Science

Biological proxies such as diatoms, foraminifers, ostracodes, and pollen allow scientists to make inferences about climate conditions in the past.

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Florence Bascom Geoscience Center

Florence Bascom Geoscience Center

Learn more about this project and its role in the Florence Bascom Geoscience Center.

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More than a third of the United States population lives in counties directly on the shoreline, making them vulnerable to hazards associated with changing sea level and storm surges associated with hurricanes and severe storms. The geologic record contains many examples of past intervals of warm climate and high sea level. "Geological Investigation of the Neogene" is examining proxy records of ocean conditions (temperature, salinity, upwelling) and the composition and distribution of marine fossil assemblages during these periods to improve understanding of potential rates, magnitudes, and impacts of change.

 

 

Coastline where water meets exposed cliff side showing geologic formation

Photo shows the Calvert Formation (created during Middle Miocene Climatic Optimum (MMCO)) taken at Plum Point on the Chesapeake Bay, in the late afternoon of October 22, 2018. 

(Credit: Harry Dowsett, USGS. Public domain.)

 

Statement of Problem: Our group reconstructs marine environments during past warm intervals using a combination of paleoclimate proxies (e.g. faunal analysis, biomarkers, stratigraphy) from well-dated sediment cores and outcrops. We also compare our paleo reconstructions with those generated by numerical ecosystem and climate models.

 

 

Why this Research is Important: We explore the environmental and economic impacts on coastal population centers under different rates and magnitudes of environmental change, using past warm climates as guides. Past warm periods provide a baseline for the impact of changes that can be used to prepare for the effects of the modern warming trend. Large segments of the U.S. population live in coastal communities which rely heavily on local fisheries, agriculture, tourism and national defense installations. This research provides valuable data to inform adaptation strategies related to the ecological health of the marine environment and the threat to infrastructure.

 

 

 

 

Fossil-rich sediment profile with hammer.

Photo shows the fossil-rich sediments of the mid-Piacenzian warm period (MPWP) that document the rapid warming and sea level rise between about 3.30 and 3.25 million years agao. The hammer is at the conformable boundary between the Rushmere (below) and Morgarts Beach (above) Members of the Yorktown Formation. 

(Credit: Harry Dowsett, USGS. Public domain.)

 

 

 

 

 

Objective(s): The research focuses on sites within the Atlantic Coastal Plain that preserve evidence from a series of past warm intervals. By documenting patterns and impacts of change during two warm intervals, the Middle Miocene Climatic Optimum (~16 Ma) and the mid-Piacenzian warm period (~3.2 Ma), the project aims to provide examples of past ecologic, environmental, and physical changes to coastal settings. These examples help anticipate the physical and economic impacts of sea surface warming and changing sea level on modern coasts and communities. In addition, through an iterative process, our results can be used to increase confidence in model projections of future change which are of increasing importance to policy makers.

 

 

Methods: We reconstruct past conditions using a variety of techniques. Distributions and abundances of different fossil assemblages can be statistically calibrated to generate estimates of temperature, salinity, productivity and seasonality. Often, the presence or morphological characteristics of individual species can be used to indicate specific environmental conditions. In addition, we analyze organic compounds, called biomarkers, to obtain independent estimates of ocean surface temperature and productivity. Stable isotopes of oxygen and carbon, found in the calcium carbonate covering of some microfossils can be used to better understand the salinity and global ice volume at the time the organism was alive. These and other types of analyses all require a sound, high resolution temporal framework constructed using calibrated first and last appearances in the fossil record of key species as well as the record of paleomagnetic reversals and select radiometric dates.

 

 

 

 

USGS scientists collecting fossils from a Calvert Formation sample site

Photo shows USGS geologists obtaining microfossil and biomarker samples from the Calvert Formation at Scientists Cliffs. 

(Credit: Harry Dowsett, USGS. Public domain.)