Stratigraphy of the Margaret Creek Formation, Corozal Basin, Northern Belize

David King and Lucille Petruny
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The informal Margaret Creek formation of northern Belize, which is a widely distributed subsurface clastic unit within the Corozal Basin, averages about 45 m in thickness and has an overall 7% porosity. The Upper Jurassic (?) to Lower Cretaceous (?) Margaret Creek unconformably overlies northern Belize basement rocks of the slightly metamorphosed Santa Rosa group (Carboniferous-Permian). The Margaret Creek is in turn conformably overlain by the informal Hill Bank formation (Lower Cretaceous ?), a clastic-bearing anhydrite and dolomite unit. At the edge of the Corozal Basin, particularly in the foothills of the Maya Mountains, some minor fault-bounded blocks provide a limited window of surface exposures, thus allowing examination of some coarse clastic facies of the Margaret Creek. One of these exposures is located on the Hummingbird highway at St. Margaret's Village, which is the de facto 'type locality.' At St. Margaret's Village, approximately 30 m of the formation crops out and the strata there are comprised of a series of fining-upward sequences. Each fining-upward sequence consists typically of a > 1 m thick, channel sand, which is overlain by < 2 m of mottled, overbank clayey sands (including paleosols). At the 'type locality,' significant portions of three distinct packages of fining upward deposits are exposed. This fluvial stratigraphy is interpreted as a succession of braided stream deposits, which formed on the flanks of the then-rising Maya Mountains. Downdip, in the deeper reaches of the Corozal Basin, the Margaret Creek includes a shale facies, which has been suggested as a possible local hydrocarbon source rock, and intercalated fluvial and marine sands. Presently, these strata are being explored as new, deep-drilling exploration targets.

AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63^rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013