Start |Author Index | View Uploaded Presentations | Meeting Information

2003 Seattle Annual Meeting (November 2–5, 2003)

Paper No. 2
Presentation Time: 1:30 PM-5:30 PM

MODERN TILEFISH MOUNDS OF ISLA COZUMEL, MEXICO


MANKIEWICZ, Carol1, WIRTH, Karl R.2, BEVIS, Martin3, DIGGINS IV, John1, DOUGLAS, Peter4, FEUCHT, Drew5, LEVEN, Chelsea6, MATHERS, Genevive2, POTEAT, Veronica7 and WALDRON, Alice4, (1)Dept. of Geology, Beloit College, 700 College St, Beloit, WI 53511-5595, (2)Geology Department, Macalester College, 1600 Grand Ave, St. Paul, MN 55105, (3)Dept. of Geology, Whitman College, Walla Walla, WA, (4)Dept. of Geology, Pomona College, Claremont, CA, (5)Dept. of Geology, The College of Wooster, Wooster, OH, (6)Dept. of Geology, Amherst College, Amherst, MA, (7)Dept. of Geology, Colorado College, Colorado Springs, CO, mankiewi@beloit.edu

Sand tilefish (Malacanthus plumieri) are important geologic agents in shallow waters of the Caribbean. These fish construct burrows in sandy environments, armoring them with pebble- to cobble-size clasts collected from the surrounding area. The resulting mounds should have a high probability for preservation throughout the Tertiary, but have yet to be recognized. The focus of our study was to more thoroughly describe tilefish mounds in modern environments to facilitate their recognition and differentiation from physical accumulations of clasts in the rock record.

We investigated characteristics of 21 mounds on a 10-km stretch of the leeward shelf of Isla Cozumel, Mexico. These mounds occur in water depths of 7 to 17 m; range in size from 0.2 to almost 3 m2; have an oval to irregular to C shape if viewed from above; are lensoid in cross section, with heights ranging from 10 to 30 cm; and contain clasts dominated by rhodoliths, corals, and mollusc shells.

Clasts on the surface of the mounds are typically 40 to 90 mm in length. This size mode is 20 to 30 mm larger than that sampled within 12 m of the mound at the same depth. We attribute the size difference to selectivity by the fish. Relative abundance of available clast types vary with proximity to reef and these variations typically are reflected in the mounds. Few other simple relationships were identified between mound characteristics and environmental indicators such as depth, sand size distribution, algal cover, and clast abundance.

We excavated one abandoned mound to determine variability of clast size and type with depth in a single mound. The 859 clasts in the upper layer show a distribution that is coarser than that shown by 3299 clasts from the bottom layer, which, in turn, is coarser than those sampled from the surroundings. Relative to the top layer, the lower part also is enriched in irregular-shaped clasts (i.e., branching coral), and depleted in rhodoliths. Thus, the mound is stratified with respect to clast size and type.

Note: Abstract also is co-authored by Stephen M. Ballou, Beloit College.

Session No. 256--Booth# 81

Sediments, Carbonates (Posters)
Wednesday, 5 November 2003: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol. 35, No. 6, September 2003, p.597
© Copyright 2003 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
Back to: Sediments, Carbonates (Posters)
<< Previous Abstract | Next Abstract >>