Geology topics

Daniel M. Robbin

Publications and source records attributed to Daniel M. Robbin.

3 recordsLinked to original sources

USGS2008

Controls on late Quaternary coral reefs of the Florida Keys

The Florida Keys is an arcuate, densely populated, westward-trending island chain at the south end of a karstic peninsular Florida Platform (Enos and Perkins 1977; Shinn et al. 1996; Kindinger el al. 1999, 2000). The "keys: mark the southernmost segment of the Atlantic continental margin of the United States. The islands are bordered by Florida Bay to the north and west, the Atlantic Ocean to the east and southeast , Gulf of Mexico to the west, and the Straits of Florida to the south. Prevailing southeasterly trade winds impinge on the keys, creating a windward margin. The largest coral reef ecosystem in the continental United States rims this margin at a distance of ~5-7km seaward of the keys and occupies a shallow (generally <12m), uneven, westward-sloping shelf (Parker and Cooke 1944; Parker et al. 1955; Enos and Perkins 1977). This platform is tectonically stable at present (Davis et al. 1992; Ludwig et al. 1996; Toscano and Lundberg 1999). The reefs and 240-km-long island chain parallel the submerged shelf margin, corresponding roughly to the 30-m depth contour that marks the base of a fossil shelf-edge reef (studies cited use the same criterion). The modern reef tract extends west-southwest from Soldier Key southeast of Miami (25°60 ′N, 80°20′W) to the Dry Tortugas in the Gulf of Mexico (24°40′N, 83 °10 ′W). Reef-tract habitats lie within the protective domain of the Florida Keys National Marine Sanctuary (Fig. 2.1.a-c; Multer 1996).

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USGS1982

Spurs and grooves revisited: construction versus erosion, Looe Key Reef, Florida

Six of 12 core holes drilled at Looe Key Reef (24°37'18"N. 81°24'24"W) by a diver-operated coring device penetrated a spur and groove system. Drilling indicated that: (II the spurs and grooves formed over at least 5 m of carbonate reef sand: (2) the underlying Pleistocene surface is essentially flat and therefore could not control or initiate spacing of spurs or grooves; (3) only the thin seaward ends of spurs are rooted on underlying bedrock: and (4) the interior of the Millepora-encrusted spurs is composed primarily of Acropora palmata. a species no longer abundant on this reef. From the drilling of Looe Key Reef and from other observations along the reef tract, we propose that most shallow spurs and grooves in active coral reef areas of the Caribbean are constructional in origin and not initiated or controlled by bedrock topography. Spurs and grooves in non-coral reef areas adjacent to shorelines, however. are clearly of erosional origin and have a close spacing distinctly different from spurs and grooves known to be of constructional origin. These observations indicate that spurs and grooves in deeper (> 15 m) fore-reef areas off Florida, which have the same geometry as the shoreline features. are erosional in origin and therefore formed on a shoreline during a lower stand of sea level.

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USGS1982

Geology and sediment accumulation rates at Carrie Bow Cay, Belize

A 24 km long transect of cores consisting of four rotary drill cores and seven vibrocores was drilled in a line extending from the seaward side of the reef crest at Carrie Bow Cay to the mainland at a point between Sittee Point and the town of Stann Creek. Two of the four rotary cores were drilled seaward of the reef crest, one through a spur to a depth of 7.6 m and the other into the adjacent groove to a depth of 18.3 m. The two cores show no evidence that the spur and groove system was erosional in origin; rather they demonstrate that it was constructional. Submarine cementation, chiefly in the form of fine-grained high-magnesium calcite, was found mainly in cemented internal sediment in both cores drilled seaward of the reef crest. Two other rotary cores were drilled landward of the reef crest. One was drilled on the reef flat to a depth of 8.8 m, and the other was drilled on the southwest tip of Carrie Bow Cay to a depth of 17.7 m. Both cores encountered essentially uncemented carbonate reef sands with some coral rubble. Of the four rotary cores, only the Carrie Bow Cay core encountered Pleistocene bedrock. Radiocarbon dating of a large head of Siderastrea siderea , growing on bedrock from the Carrie Bow Cay core at a depth of 15.04 m below sea level, gave an age of 6960±110 years. The leached calcitic coralline bedrock, at a depth of 15.7 m below sea level in the Carrie Bow Cay core, contained root marks, and iron staining indicative of subaerial exposure.

Carrie Bow Cay↗