Climatically induced sedimentary cycles in Pliocene deep-water carbonates

Conference · Fri Mar 01 04:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5677514

Gardulski, A F ^[1]

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1. 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--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (United States) Journal Volume: 75:3
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ARAGONITE
ATLANTIC OCEAN
CARBONATE MINERALS
CARBONATE ROCKS
CARIBBEAN SEA
CENOZOIC ERA
CHEMISTRY
CONTINENTAL MARGIN
CONTINENTAL SLOPE
DIAGENESIS
DOLOMITE
DRILL CORES
EXPLORATORY WELLS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGY
GULF OF MEXICO
ISOTOPE RATIO
ISOTOPES
LEVELS
MINERALOGY
MINERALS
OXYGEN ISOTOPES
PALEOCLIMATOLOGY
PALEONTOLOGY
PLIOCENE EPOCH
ROCKS
SEA LEVEL
SEAS
SEDIMENTARY ROCKS
SEDIMENTATION
STRATIGRAPHY
SURFACE WATERS
TERTIARY PERIOD
VARIATIONS
WELLS