Upper Eocene microtektites discovered in Alabama; a first-order correlation to the GPTS

Author(s): Pusz, Aimee E.; Miller, Kenneth G.; Wright, James D.; Browning, James V.; Wade, Bridget S.; Kent, Dennis V.
Author Affiliation(s): Primary:
Rutgers University, Department of Geological Sciences, Piscataway, NJ, United States
Volume Title: Geological Society of America, 2006 annual meeting
Source: Abstracts with Programs - Geological Society of America, 38(7), p.120; Geological Society of America, 2006 annual meeting, Philadelphia, PA, Oct. 22-25, 2006. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: The age and number of upper Eocene impact layers has been controversial despite several numerical age measurements of ∼35.5 Ma on a microtektite layer. There appears now to be general agreement that there are 2 upper Eocene impact layers: (1) a younger microtektite dominated layer and (2) an older clinopyroxene-bearing microkrystite layer. Microtektites have previously been found in the North and South Atlantic, Barbados, and the Caribbean Sea. Microtektites and tektites are correlated to the North American Strewn Field based on geochemical evidence and are believed to originate from the Chesapeake Bay Impact Structure. Microkrystites have been found in the Atlantic, Pacific, and Indian Oceans, and in Europe. The microkrystites are stratigraphically older than the microtektites and appear to have originated from the Popigai Crater in Siberia. One reason for the age controversy is the need for more high-resolution first-order correlation between the microtektite horizons and the geomagnetic polarity time scale (GPTS) in land-based sections. We have evaluated magnetobiostratigraphic correlations at Ocean Drilling Program Site 1090B in the South Atlantic and at St. Stephens Quarry (SSQ) in Alabama, providing first-order correlation between microtektites and the GPTS. The occurrence of microtektites and microkystites at Site 1090B can be directly tied to the GPTS using the published magnetostratigraphy. We have identified sixteen microtektites at SSQ (63.1-63.4 m) that range in size between 212 to 250 µm within the NP19/20 and P15 biozones. The microtektites are located in the North Twistwood Creek Formation and within the highstand systems tract of the Moodys Branch-NTC sequence. This is the first identification of stratigraphically in place (micro)tektites in North America. SSQ provides an excellent record of sequences and stable isotopes, providing direct evidence for the lack of long-term (>100 kyr) changes in sea level or climate in association with the impacts. At both SSQ and Site 1090, the microtektite layer occurs within the middle of Chronozone C16n.1n with a magnetochronologic age of 35.426 Ma. At Site 1090B the microkrystite layer underlies the microtektite layer and is also correlated with C16n.1n (magnetochronologic age of 35.430 Ma).
Year of Publication: 2006
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Alabama; Asia; Atlantic Ocean; Biozones; Cenozoic; Climate change; Commonwealth of Independent States; Correlation; Eocene; High-resolution methods; Leg 177; Magnetostratigraphy; Microtektites; Moodys Branch Formation; North American strewn field; North Twistwood Creek Member; ODP Site 1090; Ocean Drilling Program; Paleoclimatology; Paleogene; Paleomagnetism; Popigay Structure; Russian Federation; Saint Stephens Quarry; Sea-level changes; Siberia; South Atlantic; Tektites; Tertiary; United States; Upper Eocene
Coordinates: S425449 S425449 E0085359 E0085359
Record ID: 2008068950
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States