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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 69 (1985)

Issue: 2. (February)

First Page: 291

Last Page: 291

Title: In-Situ Rock/Water Geochemistry of Holocene Radial and Tangential Ooid Sediment, Baffin Bay, Texas: ABSTRACT

Author(s): Douglas G. Neese, John D. Pigott

Article Type: Meeting abstract


The crystal fabric in ooids from the shoreline of Kleberg Point (Baffin Bay) is predominantly tangentially oriented aragonite; however, multiple fabric elements (radial and tangential crystals) occur in ooids with mineralogies of both aragonite and 10.3-mole % magnesium calcite. Aragonite occurs as both radial and tangentially oriented crystals, whereas, high Mg-calcite exists only in a radial crystal orientation. High Mg-calcite occurs as an outermost coating surrounding aragonite, and also as an envelope about aragonite that encloses quartz nuclei.

Seasonal diurnal measurements were made in ambient bay water and water in the ooid sediment. Cyclic diurnal changes occurred in both the ambient and pore water, with the largest change occurring during the summer. Measured extremes for the summer ambient waters are: day = 32.7°C, pH of 8.22, AlkC of 3.14 meq, and H2CO3* of 10-5.07; and night = 28.3°C, pH of 8.11, AlkC of 2.54 meq, and H2CO3* of 10-4.88. Chlorinity (27.93 ^pmil), ACa2+ (2.7 × 10-3 moles/L), and AMg2+ (2.8 × 10-2 moles/L) showed little diurnal variation. Aragonite saturation was greatest during the day with ^OgrARAG-ambien = 3.25-1.95; and ^OgrARAG-pore = 4.07-2.52. Both pH and AlkC decrease with depth, whereas H2CO3* increases. The ^OgrARAG increases in the uppermost 10 cm of sediment and decreases with depth. Both ambient and pore waters are supersaturated with respect to a 10.3-mole % Mg-calcite.

Maximum ^SgrCO2 in the ooid sediment occurs during the mid-afternoon, and increases with increasing sediment depth. A decrease in H2CO3*, produced through respirative processes with increasing sediment depth, indicates that precipitation is taking place in the sediment column, as the greater proportion of H2CO3* with increasing sediment depth is caused by precipitative processes. The differing mineralogy and ooid fabric is a product of changes in both water chemistry and energy.

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