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Title: Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change

Abstract

Early Eocene to late Oligocene marine sedimentary units in southwestern Alabama were sampled at closely spaced intervals to derive a precise time-stratigraphic framework and to determine the paleoecological and mineralogical responses to fluctuations in sea level. Paleontologic control consisted of planktonic, smaller and larger benthonic foraminifera, calcareous nannofossils, dinoflagellates, and megafossils. Paleomagnetic reversals were delineated in two boreholes which, when supplemented by strontium isotope dates and the biostratigraphic control, provided a robust in situ chronostratigraphy for the Gulf Coast lower Tertiary. Paleoecologic trends in regression and transgression can be clearly correlated across major regional facies changes. Using the chronostratigraphy developed here, the second-, third-, and fourth-orders of Vail's global sea-level cycles can be recognized and demonstrate the influence of sea-level change on sedimentation. Stratigraphic systems tracts (SSTs) and bounding surfaces in outcrop were determined by lithologic variations and paleoecologic trends, and additionally by gamma logs in the cores. The lower sequence boundary occurs at a contact where an older, relatively fine-grained, deep-water, fossiliferous unit was abruptly succeeded by a coarse-grained, shallow-water, poorly fossiliferous unit. The transgressive surface occurs at the base of a fining- and deepening-upwards unit that was commonly glauconitic and very fossiliferous. Transgression culminated with a pulse ofmore » planktonic microfossils in a bed having reduced clastic sedimentation; on the log the surface of maximum starvation was marked by a gamma spike.« less

Authors:
 [1];  [2]
  1. (ARCO Oil and Gas Co., Plano, TX (United States))
  2. (ARCO Alaska, Inc., Anchorage (United States))
Publication Date:
OSTI Identifier:
7259570
Alternate Identifier(s):
OSTI ID: 7259570
Report Number(s):
CONF-910403--
Journal ID: ISSN 0149-1423; CODEN: AABUD
Resource Type:
Conference
Journal Name:
AAPG Bulletin (American Association of Petroleum Geologists); (United States)
Additional Journal Information:
Journal Volume: 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; Journal ID: ISSN 0149-1423
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; ALABAMA; GEOLOGIC DEPOSITS; SEDIMENTARY ROCKS; AGE ESTIMATION; GEOCHEMISTRY; STRATIGRAPHY; BENTHOS; FORAMINIFERA; GAMMA LOGGING; GEOLOGIC HISTORY; PALEOMAGNETISM; PALEONTOLOGY; PLANKTON; SEA LEVEL; TERTIARY PERIOD; ANIMALS; AQUATIC ORGANISMS; CENOZOIC ERA; CHEMISTRY; DEVELOPED COUNTRIES; GEOLOGIC AGES; GEOLOGY; INVERTEBRATES; LEVELS; MAGNETISM; MICROORGANISMS; NORTH AMERICA; PROTOZOA; RADIOACTIVITY LOGGING; ROCKS; SARCODINA; USA; WELL LOGGING 580000* -- Geosciences

Citation Formats

Thompson, P.R., and Baum, G.R.. Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change. United States: N. p., 1991. Web.
Thompson, P.R., & Baum, G.R.. Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change. United States.
Thompson, P.R., and Baum, G.R.. Fri . "Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change". United States.
@article{osti_7259570,
title = {Biostratigraphic, chronostratigraphic, and stratigraphic sequence analysis of Lower Tertiary marine sediments of Alabama for indicators of sea-level change},
author = {Thompson, P.R. and Baum, G.R.},
abstractNote = {Early Eocene to late Oligocene marine sedimentary units in southwestern Alabama were sampled at closely spaced intervals to derive a precise time-stratigraphic framework and to determine the paleoecological and mineralogical responses to fluctuations in sea level. Paleontologic control consisted of planktonic, smaller and larger benthonic foraminifera, calcareous nannofossils, dinoflagellates, and megafossils. Paleomagnetic reversals were delineated in two boreholes which, when supplemented by strontium isotope dates and the biostratigraphic control, provided a robust in situ chronostratigraphy for the Gulf Coast lower Tertiary. Paleoecologic trends in regression and transgression can be clearly correlated across major regional facies changes. Using the chronostratigraphy developed here, the second-, third-, and fourth-orders of Vail's global sea-level cycles can be recognized and demonstrate the influence of sea-level change on sedimentation. Stratigraphic systems tracts (SSTs) and bounding surfaces in outcrop were determined by lithologic variations and paleoecologic trends, and additionally by gamma logs in the cores. The lower sequence boundary occurs at a contact where an older, relatively fine-grained, deep-water, fossiliferous unit was abruptly succeeded by a coarse-grained, shallow-water, poorly fossiliferous unit. The transgressive surface occurs at the base of a fining- and deepening-upwards unit that was commonly glauconitic and very fossiliferous. Transgression culminated with a pulse of planktonic microfossils in a bed having reduced clastic sedimentation; on the log the surface of maximum starvation was marked by a gamma spike.},
doi = {},
journal = {AAPG Bulletin (American Association of Petroleum Geologists); (United States)},
issn = {0149-1423},
number = ,
volume = 75:3,
place = {United States},
year = {1991},
month = {3}
}

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