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Pore-water chemistry from the ICDP-USGS coer hole in the Chesapeake Bay impact structure--Implications for paleohydrology, microbial habitat, and water resources

Special Paper of the Geological Society of America

By:
, , , , , , and
DOI: 10.1130/2009.2458(36)

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Abstract

We investigated the groundwater system of the Chesapeake Bay impact structure by analyzing the pore-water chemistry in cores taken from a 1766-m-deep drill hole 10 km north of Cape Charles, Virginia. Pore water was extracted using high-speed centrifuges from over 100 cores sampled from a 1300 m section of the drill hole. The pore-water samples were analyzed for major cations and anions, stable isotopes of water and sulfate, dissolved and total carbon, and bioavailable iron. The results reveal a broad transition between fresh and saline water from 100 to 500 m depth in the post-impact sediment section, and an underlying syn-impact section that is almost entirely filled with brine. The presence of brine in the lowermost post-impact section and the trend in the dissolved chloride with depth suggest a transport process dominated by molecular diffusion and slow, compaction-driven, upward flow. Major ion results indicate residual effects of diagenesis from heating, and a pre-impact origin for the brine. High levels of dissolved organic carbon (6-95 mg/L) and the distribution of electron acceptors indicate an environment that may be favorable for microbial activity throughout the drilled section. The concentration and extent of the brine is much greater than had previously been observed, suggesting its occurrence may be common in the inner crater. However, groundwater flow conditions in the structure may reduce the salt-water-intrusion hazard associated with the brine.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Pore-water chemistry from the ICDP-USGS coer hole in the Chesapeake Bay impact structure--Implications for paleohydrology, microbial habitat, and water resources
Series title:
Special Paper of the Geological Society of America
DOI:
10.1130/2009.2458(36)
Volume
458
Year Published:
2009
Language:
English
Publisher:
Geological Society of America
Contributing office(s):
Branch of Regional Research-Eastern Region
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Special Paper of the Geological Society of America
First page:
867
Last page:
890
Country:
United States