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ORIGIN AND DISTRIBUTION OF CALCAREOUS FINES ON THE CAROLINA CONTINENTAL SHELF
Author(s) -
MOLNIA BRUCE F.,
PILKEY ORRIN H.
Publication year - 1972
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1972.tb00016.x
Subject(s) - foraminifera , geology , aragonite , carbonate , calcite , continental shelf , halimeda , calcareous , continental margin , oceanography , calcium carbonate , sediment , mineralogy , paleontology , chemistry , tectonics , organic chemistry , benthic zone
The fine carbonate fraction (less than 63 μ in diameter) in 175 sediment samples collected from the Carolina continental margin has been studied. This fraction, generally under 5% of the total sample, averages 43% CaCO 3 . By comparison, the CaCO 3 fraction of the total samples averages only 25%. On the inner shelf, the percentage CaCO 3 in the fine fraction is twenty or more times greater than the percentage CaCO 3 in the total sample. With increased distance offshore, the percentages of CaCO 3 in the fine fraction and the total sample approach equality. Beyond the shelf break the percentage of CaCO 3 in the total sample is greater than that in the fines. The CaCO 3 faunal components are primarily foraminifera, fragments of foraminifera, mollusc‐barnacle fragments and echinoid material. Minor constituents include alcyonarian and tunicate spi‐cules, Halimeda and other calcified green algae. Many grains are bored and show solution effects. The coarse carbonate fraction shows distinct regional faunal assemblages, but the fines are essentially uniformly distributed. Two exceptions are a zone of mollusc fragments around Cape Hatteras and a foraminifera zone on a portion of the outer shelf. The average carbonate mineral assemblage consists of 44% low‐Mg calcite, 38% aragonite and 18% high‐Mg calcite. The principal modes of origin of calcareous fines on the Carolina continental margin are probably biological and physical destruction of coarser particles and primary formation in fine size fraction (as in the case of some foraminifera).