Hen and Chickens Shoal, Delaware: evolution of a modern nearshore marine feature
Date
1984
Authors
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Publisher
University of Delaware
Abstract
The use of modern analogs to deduce the position and geometry of ancient deposits is an important geologic technique. Hen and Chickens Shoal, Delaware was choosen as a modern analog because of its distinct geomorphology, and the large amount historical data. The historical migration, present sedimentary texture, hydrodynamics, and stratigraphy were integrated into a model of shoal origin and maintenance. The shoal may be shown to be three morphological parts, (head, body, and tail) that migrate in three different directions, (northwest, west, and southeast), at three separate rates, (11 meters/year, 12 meters/year, and 25 meters/year), respectively. The mechanism for shoal origin and maintenance may be broken down into four parts, (supply, distribution, modification/sorting, and sorting), which correspond to flood tidal currents, ebb tidal currents, transitional and helical currents, and waves, respectively. The helical flow model is proposed as the most applicable model for the origin and maintenance of Hen and Chickens Shoal. The sedimentary textures associated with Hen and Chickens Shoal may be recognized from other sediments based on the following criteria: l) grain size parameters and 2) probabiity curves. The migration, in time and space, of the sedimentary textures produces a nearshore marine lithosome that may be preserved in the geologic record. Hen and Chickens Shoal is proposed as a typical linear type estuarine inlet associated shoal.