RECOGNIZING TILEFISH MOUNDS IN THE ROCK RECORD: MOUND SIZE AND ENVIRONMENT ON THE WESTERN COAST OF COZUMEL, MEXICO

Sand tilefish, Malacanthus Plumieri, build mounds of sedimentary clasts on the ocean floor that serve as protection from predators. These mounds have not been seen in the fossil record, but if found it is possible that mound characteristics could indicate the depositional environment in which they were built. The modern mounds are significant sedimentary structures, averaging 0.1 m3 in volume. As part of the Keck Geology Consortium Cozumel Project we investigated the relationship between depositional environments and the physical characteristics of 21 mounds in shallow water off the west coast of Isla Cozumel, Mexico. We found the mounds were present and common in all depositional environments to a depth of 20 meters. We recorded the depth, size, and types of clasts used to construct each mound, as well as the availability and type of clasts surrounding each mound. Data analysis indicated no clear relationship between the size of mounds and various environmental factors, including depth, availability of clasts, distance from a reef, and the grain size of sediments surrounding the mound. As the mounds were common in the shallow water environments studied, fossil mounds are likely present in Pleistocene shallow water rock facies on Isla Cozumel.