Comparative planktonic foraminiferal aminostratigraphy of the Colombia basin and the northeast Gulf of Mexico

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5529476

Fletcher, R R; Wehmiller, J F; Martin, R E; Johnson, B J ^[1]

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1. Univ. of Delaware, Newark (United States)

The increase in the proportion of D-amino acids in fossil shells with increasing age can be used as a relative dating method as far back as the mid-Miocene. Planktonic foraminiferal biostratigraphy and mixed foraminiferal aminostratigraphy were determined for DSDP Site 502B (late Pliocene-Pleistocene) and 502A (late Miocene-Pliocene) in the Colombia basin. The aminostratigraphic analysis was conducted every 2.5-5.0 m in the Pleistocene and every 5-10 m in the Pliocene. Previously established planktonic foraminiferal datums and subzonal boundaries were used to establish the geochronology of DSDP Site 502B-502A. Sediment accumulation rates were then calculated and used to estimate the absolute age at a particular depth in each core. Aminostratigraphic analysis indicates a logarithmic increase in D-alloisoleucine/L-isoleucine (A/I) ratios with increasing age, where equilibrium is not reached until ca. 5 Ma. Using the logarithmic curve that best fits the A/I data, one can estimate the numerical age of a bulk sample given the A/I ratio. The mixed species assemblage A/I ratios from ODP Site 625B (Gulf of Mexico) and 502B are comparable from the late Pliocene-Pleistocene, which suggests that aminostratigraphic analysis of a mixed foraminiferal assemblage offers a very useful and unique opportunity to estimate ages in other Pliocene-Pleistocene sections in regions where independent geochronologic control may be lacking.

• OSTI ID: 5529476
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
COLOMBIA
SEDIMENTARY BASINS
GULF OF MEXICO
STRATIGRAPHY
AGE ESTIMATION
AMINO ACIDS
BIOLOGICAL MARKERS
COMPARATIVE EVALUATIONS
EXOSKELETON
FORAMINIFERA
FOSSILS
PLANKTON
TERTIARY PERIOD
ANIMALS
AQUATIC ORGANISMS
ATLANTIC OCEAN
BODY
CARBOXYLIC ACIDS
CARIBBEAN SEA
CENOZOIC ERA
DEVELOPING COUNTRIES
EVALUATION
GEOLOGIC AGES
GEOLOGIC STRUCTURES
GEOLOGY
INVERTEBRATES
LATIN AMERICA
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
PROTOZOA
SARCODINA
SEAS
SKELETON
SOUTH AMERICA
SURFACE WATERS
580000* - Geosciences