Re-calibration of the apparent 25,000 to 35,000 ybp sea level high stand: Just a moment in time some 55,000 to 70,000 years ago
- Univ. of North Carolina, Wilmington, NC (United States). Dept. of Earth Sciences
Occurrences of shallow marine and strand line sediments at or near the elevation of modern mean sea level with radiocarbon dates in the range of 25,000--35,000 ybp have been reported from the Delmarva Peninsula to the Florida Peninsula. Such dates are in conflict with established sea level curves and have consequently been written off as much older samples contaminated with small amounts of young carbon. An alternate hypothesis is that the assumed near constancy of the galactic cosmic ray (GCR) flux and consequently the C-14 production rate is not totally correct. Be-10 concentrations from ice cores suggests that possibly twice in the last 100,000 years the earth has been briefly subjected to greatly enhanced GCR fluxes. Modeling effects of the increased but brief GCR flux on the total C-14 concentrations in the ocean and biosphere suggests that apparent C-14 dates of 25K to 35K ybp on certain marine deposits may actually reflect deposition during a very brief period of time somewhere between 55K to 70K ybp. Deposits possibly effected include but are not restricted to: an unnamed beach/shore face deposit at Mockhorn Is. Virginia, Diamond City Clay at Cape Lookout NC, Cape Fear Coquina in southeastern NC, Silver Bluff at Sapelo Is. GA, and an unnamed coarse sand at St. George Is., FL. Such deposits are depositionally associated with strand line processes, either near shore, beach, or estuarine. Characteristics of the C-14 dates from such deposits include great variability in age ranges for spatially close samples including association with non-finite samples and apparent violation of the principle of superposition where older material overlies apparently younger. Interpretation of such deposits suggest deposition at or near sea level during a period of falling sea level. Correlation of such deposits north to south along the Atlantic coast suggest continued influence of the glacial forebulge and deposition topographically 5 to 10 meters below modern mean sea level.
- OSTI ID:
- 6120284
- Report Number(s):
- CONF-9304188-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:4; Conference: 42. annual Geological Society of America (GSA) Southeastern Section meeting, Tallahassee, FL (United States), 1-2 Apr 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC DEPOSITS
AGE ESTIMATION
US EAST COAST
PALEOCLIMATOLOGY
BERYLLIUM 10
CARBON 14
COASTAL REGIONS
COSMIC RAY FLUX
DRILL CORES
ERRORS
ICE CAPS
ISOTOPE DATING
SEA LEVEL
ALKALINE EARTH ISOTOPES
BERYLLIUM ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CARBON ISOTOPES
DEVELOPED COUNTRIES
EVEN-EVEN NUCLEI
ICE
ISOTOPES
LEVELS
LIGHT NUCLEI
NORTH AMERICA
NUCLEI
PALEONTOLOGY
RADIATION FLUX
RADIOISOTOPES
USA
YEARS LIVING RADIOISOTOPES
580000* - Geosciences