Inner-shelf hardbottom areas, northeastern Gulf of Mexico

Conference · Thu Sep 01 04:00:00 EDT 1988 · AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States)

OSTI ID:6375077

Schroeder, W W; Shultz, A W; Dindo, J J

Indurated sediments are common on the sea floor of offshore Alabama and northwestern Florida in water depths of 18 to 40 m. Hardbottom areas include reeflike outcrops with up to 2 m of relief above the surrounding sea floor, moderately sloping ridges of rock rubble and shell hash, and areas of surficial rock and shell rubble with little or no relief. Although most of these hardbottoms are classified as live (i.e., they support a diverse encrusting epifauna), their composition and texture indicate formation under different prior conditions. Four types of hardbottom rock are identified: (1) massive to nodular sideritic sandstones and mudstones, widely distributed in the central and western portions of the area; (2) slabby aragonite-cemented coquina and sandstone in the central part of the area, mostly rubble associated with storm-related ridges of shell and sand; (3) dolomitic sandstone in small irregular outcrops, compositionally related to (2); and (4) calcite-cemented algal calcirudite in reeflike knobs in the southeastern portion of the area. In all but (4), mineralogy and isotope ratios suggest that cementation took place via marine rather than fresh waters, and that methane and plant detritus served as carbon sources. Most mappable hardbottom areas are rubble zones on northeast-facing slopes of gentle low-relief shore-oblique ridges. Thus, present-day extent of hardbottoms is a function not only of original deposition and cementation patterns but also represents a response to modern shelf processes such as energetic storm events.

• Research Organization: Univ. of Alabama, Dauphin (USA)
• OSTI ID: 6375077
• Report Number(s): CONF-8810362-
• Conference Information: Journal Name: AAPG (Am. Assoc. Pet. Geol.) Bull.; (United States) Journal Volume: 72:9
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
ALABAMA
ALKALINE EARTH METAL COMPOUNDS
ATLANTIC OCEAN
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CARIBBEAN SEA
DEPOSITION
FEDERAL REGION IV
FLORIDA
GULF OF MEXICO
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
ROCKS
SEAS
SEDIMENTARY ROCKS
SURFACE WATERS
USA