Holocene deposition in Northwest Providence Channel, Bahamas: a geochemical approach

Thesis/Dissertation · Sun Jan 01 04:00:00 EST 1978

OSTI ID:5413499

Boardman, M R

The origins and depositional history of Holocene sediment in Northwest Providence Channel, Bahamas (NWPC) have been determined using geochemical measurements coupled with textural data, petrographic examination, and scanning electron microscopy. Most of the channel is 200 to 2000 m deep, and nearly 100% of the sediment is calcium carbonate. Shallow water platform sources contribute 75-90% of the Holocene sediment in NWPC. Bank derived sand is most abundant near the platforms (nearly 100%) and is concentrically distributed around a central area of abundant non-platform sand. Bank-derived mud (<62 ..mu..m) accounts for more than 80% of the mud fraction in NWPC. The coarse silt (62-16 ..mu..m), fine silt (16-4 ..mu..m) and clay (< 4 ..mu..m) fractions from LLB (Bight of Abaco) are geochemically distinct from the mud fractions of Great Bahama Bank (GBB). Their distributions in NWPC demonstrate that both platforms are significant sediment contributors to NWPC. The observed sediment distribution clearly indicates that significant off bank transport occurs. With regard to sediment transport, no windward or leeward effects are observed in Holocene sediment deposition. Gravity flow processes are not significant to Holocene deposition. 80% of the present sedimentation rate results from the banktop flooding and confirms that 75%-90% of the Holocene sediment is derived from platform sources. The C-14 dated Holocene sediment layer is approximately 50 cm thick, and its transition with the Pleistocene occurs over a vertical interval of less than 20 cm as a result of mixing by benthonic organisms. This Holocene sediment layer should remain intact to permanently record this banktop episode, and should have a different diagenetic future from the underlying stable (calcite-rich) sediment.

• Research Organization: North Carolina Univ., Chapel Hill (USA)
• OSTI ID: 5413499
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580500* -- Oceanography-- (1980-1989)
ALKALINE EARTH METAL COMPOUNDS
BAHAMA ISLANDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATES
CENOZOIC ERA
CHEMISTRY
DEPOSITION
DEVELOPING COUNTRIES
ELECTRON MICROSCOPY
GEOCHEMISTRY
GEOLOGIC AGES
HISTORICAL ASPECTS
ISLANDS
MICROSCOPY
ORIGIN
OXYGEN COMPOUNDS
PETROGRAPHY
QUATERNARY PERIOD
SAND
SCANNING ELECTRON MICROSCOPY
SEDIMENTS
TEXTURE
WEST INDIES