ABSTRACT: Tectonics and Structural Control of Sedimentation along the Monkey River and Big Creek, Southern Belize, C.A.

GRIES, J. C., and W. E. FULL, Wichita State University, Wichita, KS

Big Creek is a short river draining the flat coastal plain at the edge of the North American Plate, south-central Belize. Recent sediments in this river consist of fine-grained silts and clays derived from the coastal plain with occasional coarser-grained lenses. Offshore from Big Creek are sand bars, channels, and eroding islands consisting of well-sorted, coarse sand comprised dominantly of feldspathic minerals. The configuration of these sands suggests Big Creek was the source for this material. The sedimentological implication is that the nearshore and offshore parts of Big Creek represent a drowned deltaic complex.

One explanation for the texture and geometry of these sediments is that Big Creek was shortened by stream piracy influenced by regional tectonics. In this model, the sands were originally derived from the Maya mountains. Field observations have tended not to support this explanation. A more likely source for the coarse sand appears to be the local soil horizon. Sand lenses consisting of coarse material appear to be associated with the top of the water table and suggest this material is related to soil weathering and subsequent redeposition. These observations suggest that there are instances where coarse sandstones may be indicative of a local soil horizon and not necessarily the direct result of related transportation from distant terrains. This explanation presents an alternate mode for lower Morrow siliciclastic deposition in the present subsurface of the Great Plains.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)