ANALYSIS OF THE LARES LIMESTONE CARBONATE SEQUENCE EXPOSED ON THE ROAD PUERTO RICO # 111 BETWEEN KM 27.1 TO 27.5

A sequence stratigraphy analysis was performed to study the Oligocene Lares Limestone exposed between kilometers 27.1 to 27.5 on road PR#111, in San Sebastian, Puerto Rico. This 500 meters exposure was photographed from a Sky Hawk Cessna Airplane and digitally mapped. This outcrop is probably the most complete exposure of the Lares Limestone in Puerto Rico. The lower contact with the San Sebastion Formation and the upper contact with the Montebello Mbr. of the Cibao Formation are exposed. In this research we analyzed the exposure in terms of sequence stratigraphy and a stratigraphic column along with a photomosiac of the outcrop were produced. Lithology and diagnostic constituents allowed us to determine depositional environments and shallowing upward sequences were interpreted. The units recognized were grouped into nine different parasequences along the outcrop. The parasequences on the outcrop are characterized by starting with siltstones that gradually develop into coral boundstone toward the top. The Lares Limestone is here interpreted to represent a transgressive system tract (TST), a maximum flooding surface and a Highstand System Tract (HST). The thickness of the parasequences changes, thickening and thinning as we move up the section from the TST to the HST. The contact with the Monte Bello Mbr. is characterized by a paleosol representing aerial exposure and interpreted here as a sequence boundary. The Monte Bello Mbr. is composed of prograding clinoforms.