Late Pleistocene Bays and Reefs: Ancestors to the Modern Caribbean Coast, Yucatán Península, México
Date of this Version
Shaw, C. E. , 2016, Late Pleistocene Bays and Reefs: Ancestors to the Modern Caribbean Coast, Yucatan Peninsula, Mexico: Journal of Coastal Research, v. 32, n. 2, 2016.
Low-lying indentations along the modern Caribbean coast of the Yucatán Peninsula host shallow bays with classic crescent-shaped, white-sand beaches. These indentations have previously been explained as products of Holocene dissolution of Pleistocene limestones within a brackish coastal mixing zone. This paper demonstrates that the lows confining the modern bays were formed by sedimentary processes 122,000 ± 2000 YBP, during the late Pleistocene. A 50 km stretch of the Caribbean coast between Tankah and Playa del Carmen, here called the high coast, is characterized by rocky headlands that are underlain by fossilized coral reefs of late Pleistocene age and lows between headlands occupied by modern bays. Study of landforms using aerial photographs together with field examination of late Pleistocene calcarenite exposed in quarries has led to recognition of a series of arcuate Pleistocene beaches with large attached spits that developed during a period of falling sea level that followed the oxygen isotope substage 5e sea-level highstand. Pleistocene beaches and associated triangular spits form a series of cuspate arcs, each precisely aligned with one of the modern bays and each triangular spit aligned with the center of a modern headland. This exact and repeated coincidence of substage 5e bays with modern bays and beaches indicates that low areas occupied by modern bays lie within the lowest portions of late Pleistocene bays that were drained during the Wisconsin glacial and reflooded in their lowest parts during the post-Wisconsin rise of sea level in the Holocene.