Hornblende content of Georgia-South Carolina, U.S.A., nearshore sands; support for shoreward sediment transport in the nearshore zone

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doi: 10.1016/0037-0738(88)90024-3
Authors:Schmitter, R. D.; Freeman-Lynde, R. P.
Author Affiliations:Primary:
Univ. Ga., Dep. Geol., Athens, GA, United States
Volume Title:Sedimentary Geology
Source:Sedimentary Geology, 57(3-4), p.153-169. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0037-0738
Publication Date:1988
Note:In English. 50 refs.; illus. incl. 2 tables
Summary:Core top samples from 51 box cores taken about 1 km apart in several transects off Hilton Head Island, South Carolina, and Tybee, Wassaw and Ossabaw Islands, Georgia, have been analysed for heavy-mineral composition of acid-insoluble 3-2 φ fractions to determine hornblende content, and for acid-soluble (principally calcium carbonate plus carbonate fluorapatite) content, and grain size data for acid-insoluble sand and gravel fractions (< 4 φ) and for unacidified samples. Heavy-mineral contents of acid-insoluble 3-2 φ fractions range from 0.2 to 2.3%, with hornblende and epidote the most abundant heavy minerals. Individual hornblende and epidote abundances range from 16.2 to 52.0%. Hornblende and epidote contents vary antithetically, with maxima in hornblende content and minima in epidote content at nearshore and offshore ends of transects, and with minima in hornblende content and maxima in epidote content over middle portions of transects. Ilmenite is the most abundant opaque mineral identified, with abundances from 1.3 to 24.5%. Ilmenite maxima are associated with hornblende minima at several stations off Hilton Head and Tybee Islands, apparently due to winnowing. Acid-insoluble residues are very fine to fine (4-2 o) sands, with very fine sand (Recent) dominant within 5 km of shore and fine sand (relict, or palimpsest) most abundant farther offshore. Acid-soluble contents in the study area are < 25% of total sample weight for nearly all samples analysed, and are often < 15%. High hornblende contents at seaward ends of transects indicate shoreward transport of hornblende-rich sediments from the adjacent inner continental shelf. Low hornblende contents in middle portions of transects indicate dilution of hornblende-rich sands by hornblende-poor Coastal Plain sediments derived from Coastal Plain rivers, and exposed by shoreface erosion 4-8 m deep, and by tidal inlet erosion. High hornblende contents at nearshore ends of transects reflect contributions of hornblende-rich sediment from Piedmont rivers at the nearshore zone. [Authors' abstract] - R. [M.F.P.]
Subjects:Amphibole group; Cenozoic; Chain silicates; Clastic sediments; Clinoamphibole; Continental shelf; Epidote; Epidote group; Grain size; Gravel; Heavy minerals; Holocene; Hornblende; Ilmenite; Marine sediments; Marine transport; Mechanism; Mineral composition; Nearshore environment; Oceanography; Orthosilicates; Oxides; Quaternary; Sand; Sedimentation; Sediments; Silicates; Sorosilicates; Transport; Atlantic Coastal Plain; Beaufort County South Carolina; Bryan County Georgia; Chatham County Georgia; Georgia; South Carolina; United States; Hilton Head Island; Ossabaw Island; Tybee Island; Wassaw Island
Coordinates:N321300 N321500 W0804000 W0804200
Abstract Numbers:89M/1256
Record ID:1988050864
Copyright Information:GeoRef, Copyright 2021 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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