Delineation of Calcite-Cemented Layers in Holocene Skeletal Carbonate Sands, San Salvador, Bahamas

CARNEY, CINDY, DAVID DOMINIC, and KATHLEEN EGAN, Wright State University, Dayton, OH, and MARK BOARDMAN, Miami University, Oxford, OH

A number of methods were employed to determine stratigraphic and diagenetic variations within a Holocene carbonate strand plain on Sandy Hook, San Salvador, Bahamas. The strand plain (5 km2) directly abuts a Pleistocene ridge from which it has prograded 1.5 km. The upper 1 m of strand-plain sediments consists of uncemented, homogeneous, medium bioclastic sand. The next 1 m is partly cemented medium to coarse sand with some textural and compositional stratification. Below the cemented layer are unconsolidated sands with partially cemented clasts. The entire sequence is approximately 12 m thick and overlies Pleistocene rock.

A combination of vibracoring and rotary coring using a modified double-tube core barrel allowed partial recovery of cemented and uncemented sands whereas augering simply homogenized partially cemented material. Seismic reflection and refraction did not have sufficient resolution to distinguish cemented layers but were capable of identifying the Holocene/Pleistocene contact and the water table.

The areal extent of cemented layers was delineated primarily by ground-penetrating radar. A total of 2 km of continuous profiles were collected from various parts of the strand plain including transects both parallel and transverse to the current beach face. Signal penetration below the uppermost cemented layer was limited and details of the distribution of multiple layers are poorly known. Nevertheless, it is apparent that early cementation within these sediments has been widespread.

AAPG Search and Discovery Article #91005 © 1991 Eastern Section Meeting, Pittsburgh, Pennsylvania, September 8-10, 1991 (2009)