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E.A. Shinn

Publications and source records attributed to E.A. Shinn.

43 records · Page 3Linked to original sources
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.

Florida↗
USGS1980

Geologic history of Grecian Rocks, Key Largo Coral Reef Marine Sanctuary.

Two transects were drilled across the major ecologic zones of the c. 750 by 200 m reef, whose accumulation was controlled by a local Pleistocene topographic feature. The Reef is composed of 5 major ecologic zones: 1) a deep seaward rubble zone, 6-8 m depth; 2) a poorly developed spur and groove zone composed of massive head corals and Millepora (4-6 m water depth); 3) a characteristic high-energy oriented Acropora palmata zone extending from the surface down to 4 m; 4) a distinct broad reef flat composed of in situ A. palmata and coral rubble, followed by 5) a narrow low- energy back-reef zone of unoriented A. palmata, thickets of A. cervicornis, and various massive head corals in water 0-3 m deep. An extensive grass-covered carbonate sand flat 3-4 m deep extends in a landward direction from zone 5. - from Author

Bulletin of Marine Science↗
USGS1978

Oxygen and carbon isotopic growth record in a reef coral from the Florida Keys and a deep-sea coral from Blake Plateau

Carbon and oxygen isotope analysis through a 30-year (1944 to 1974) growth of Montastrea annularis from Hen and Chickens Reef (Florida Keys) shows a strong yearly variation in the abundances of both carbon-13 and oxygen-18 and a broad inverse relationship between the two isotopes. Normal annual dense bands are formed during the summer and are characterized by heavy carbon and light oxygen. "Stress bands" are formed during particularly severe winters and are characterized by heavy carbon and heavy oxygen. The isotopic effect of Zooxanthellae metabolism dominates the temperature effect on the oxygen-18/oxygen-16 ratio. The isotopic results on the deep-sea solitary coral Bathypsammia tintinnabulum , where Zooxanthellae are nonexistent, indicates that the abundance of the heavy isotopes carbon-13 and oxygen-18 is inversely related to the growth rate, with both carbon and oxygen approaching equilibrium values with increasing skeletal age.

Florida↗
USGS1977

Topographic control and accumulation rate of some Holocene coral reefs: south Florida and Dry Tortugas

Core drilling and examination of underwater excavation on 6 reef sites in south Florida and Dry Tortugas revealed that underlying topography is the major factor controlling reef morphology. Carbon-14 dating on coral recovered from cores enables calculation of accumulation rates. Accumulation rates were found to range from 0.38 m/1000 years in thin Holocene reefs to as much as 4.85 m/1000 years in thicker buildups. Cementation and alteration of corals were found to be more pronounced in areas of low buildup rates than in areas of rapid accumulation rates. Acropora palmata, generally considered the major reef builder in Florida, was found to be absent in most reefs drilled. At Dry Tortugas, the more than 13-meter thick Holocene reef did not contain A. palmata. The principal reef builders in this outer reef are the same as those which built the Pleistocene Key Largo formation, long considered to be fossilized patch reef complex.

Florida↗
USGS1977

Recent and relict topography of Boo Bee patch reef, Belize

Five core borings were taken on and around Boo Bee Patch Reef to better understand the origin of such shelf lagoon reefs. The cores reveal 4 stages of development: (1) subaerial exposure of a Pleistocene "high" having about 8 meters of relief, possibly a Pleistocene patch reef; (2) deposition of peat and impermeable terrigenous clay 3 meters thick around the high; (3) initiation of carbonate sediment production by corals and algae on the remaining 5 meters of hard Pleistocene topography and carbonate mud on the surrounding terrigenous clay; and (4) accelerated organic accumulation on the patch reef. Estimates of patch reef sedimentation rates (1.6 m/1000 years) are 3 to 4 times greater than off-reef sedimentation rates (0.4-0.5 m/1000 years). During periods of Pleistocene sedimentation on the Belize shelf, lagoon patch reefs may have grown above one another, stacking up to form reef accumulation of considerable thickness.

Conference Paper↗