Climatically induced sedimentary cycles in Pliocene deep-water carbonates
- Tufts Univ., Medford, MA (United States)
Two DSDP sites (86 and 94) on the Campeche ramp in the southern Gulf of Mexico penetrated more than 100 m of Pliocene pelagic ooze. The ooze is primarily carbonate, with a much smaller volcanic ash component than occurs in some Pleistocene sediments at these sites. Cores recovered from these holes display variations in carbonate mineralogy as well as total carbonate and sand abundances that are correlated with the oxygen isotope stratigraphy. Diagenetic loss of Mg-calcite is complete by the base of the Pleistocene, but aragonite, especially high-Sr aragonite forming algal needles that were transported off the shelf to the slope, persists through upper Pliocene cores. Variations in oxygen isotope ratios in planktonic foraminifera occur throughout the Pliocene, although the amplitude of those cycles is smaller than for the Pleistocene, with its more dramatic glacial-interglacial contrasts. As in overlying Pleistocene slope sediments, cooler intervals correspond with greater abundances of aragonite in the upper Pliocene section, reflecting a shift of the shallow, productive shelf seaward across the ramp surface during times of relatively low sea level. However, the aragonite abundances in the Pliocene are reduced on average compared to the Pleistocene. This difference is due in part to diagenetic loss, but also it likely reflects the overall higher sea level that apparently characterized Pliocene oceans, trapping more algal aragonite landward. Although sea level and climatic fluctuations were indeed less extreme in the Pliocene, they were still sufficient to generate sedimentary cycles in deep-water carbonates.
- OSTI ID:
- 5677514
- 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
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Related Subjects
CARBONATE ROCKS
DIAGENESIS
GEOCHEMISTRY
CONTINENTAL SLOPE
STRATIGRAPHY
GULF OF MEXICO
PALEOCLIMATOLOGY
ARAGONITE
DOLOMITE
DRILL CORES
EXPLORATORY WELLS
ISOTOPE RATIO
MINERALOGY
OXYGEN ISOTOPES
PLIOCENE EPOCH
SEA LEVEL
SEDIMENTATION
VARIATIONS
ATLANTIC OCEAN
CARBONATE MINERALS
CARIBBEAN SEA
CENOZOIC ERA
CHEMISTRY
CONTINENTAL MARGIN
GEOLOGIC AGES
GEOLOGY
ISOTOPES
LEVELS
MINERALS
PALEONTOLOGY
ROCKS
SEAS
SEDIMENTARY ROCKS
SURFACE WATERS
TERTIARY PERIOD
WELLS
580000* - Geosciences