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CRAMP Rapid Assessment. Sediment Grain Size
Subsamples are taken from each of two replicate samples collected from every transect. Standard brass sieves are used to determine size fractions: 2.8 mm, 500 um, 250 um, and 63 um (USA Standard Testing Sieve: A.S.T.M.E.-11 specifications). A brass catch pan is used to collect the silt/clay fraction. Five size fractions are determined: granule (>2.8 mm), coarse and very coarse sand (500 um-2.8 mm), medium sand (250-500 um), fine and very fine sand (63-250 um), and silt/clay (<63 um) in accordance with the Wentworth scale (Folk 1974). Each size fraction is collected in pre-weighed Whatman 114 wet strength filters, air dried and weighed to determine the proportion of each size fraction. Extremely large pieces are removed prior to sorting to reduce variability and eliminate overweighting of some samples by a single piece of material. Only the four smallest size fractions are used in the analyses.
References:
Folk, R. L. 1974. Petrology of sedimentary rocks. Hemphill Publishing Company. Austin, TX, USA.
Last Update: 04/21/2008
By: Lea Hollingsworth
Hawai‘i Coral Reef Assessment & Monitoring Program
Hawai‘i Institute of Marine Biology
P.O. Box 1346
Kāne‘ohe, HI 96744
808-236-7440 phone
808-236-7443 fax
email: jokiel@hawaii.edu