Constituent Particle Analysis of Reefal Sediments from the Houtman-Abrolhos Islands, Western Australia

April 29th, 2006

Constituent particle analyses have been applied to many different sedimentary environments, especially in the Bahamas and the Caribbean, but have rarely been used in analyzing sediments from Western Australia. This study compared sediment samples collected from modern and
Pleistocene reef environments in the Houtman-Abrolhos Islands off the coast of Western Australia. The archipelago is located approximately 100km off the coast of Australia, in the Leeuwin Current, and is located in a region of overlap between the tropical and temperate biogeographic marine provinces. A total of ten samples were collected from Pleistocene and modern environments: seven Pleistocene samples were taken from fossil coral reef assemblages exposed on East Wallabi Island and three were taken from modern coral reefs adjacent to East Wallabi in Turtle Bay. Five of the fossil samples were unconsolidated while the other two were not. Each sample was made into a thin-section slide and then analyzed under a microscope. A point-count was done on each slide, which entails moving the slide one millimeter in each direction and identifying the particle under the cross-hairs. A total of 2,903 counts were made. Overall it was discovered that most samples consisted mainly of coral and algae. The results from both the modern and the Pleistocene samples show that their constituents are analogous suggesting the Pleistocene exposures preserve a reef environment similar to the modern reef offshore.

Jessica Harms, ’06 Peterborough, NH
Majors: Environmental Studies, Geology

Sponsor: Benjamin Greenstein

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