Petrographic characteristics of a Holocene carbonate grainstones in southeast San Salvador, Bahamas: Implications for the sediment reworking in a high energy lagoon

Abstract

The southeast corner of San Salvador, Bahamas is comprised of several Holocene sedimentary environments in which carbonate sediments are accumulating. Some of these deposits have been lithified to form grainstones, others are not yet lithified. These environments are strand plain (Sandy Hook), dunes (Holocene and Pleistoncene), high energy lagoon (Snow Bay), and tidally-influenced lagoon (Pigeon Creek). These high energy environments are laterally and vertically linked forming different compartments of a carbonate grainstone/packstone body. Petrographic study reveals that these sediments and grainstones are similar in grain composition and texture. The dominant grains are peloids, ooids, and skeletal grains such asHalimeda and foraminifera. Other minor components are bivalves, gastropods, grapestones and intraclasts. Most grains in the Sandy Hook strand plain and the dunes are characterized by abraded grains whereas grains in subtidal sands (Snow Bay and Pigeon Creek) are well preserved. The increasing pattern of ooids with depth in the lagoon and strand plain sediments and the high percentage of ooids in Holocene dune samples suggests that ooid generation occurred early in the Holocene and that subsequently ooids were transported to dunes, and the strand plain. Diagentic characteristics of ooids and also support movement of sand size grains. Clasts in both early and late Holocene deposits are commonly comprised of ooids which are cemented with blocky calcite cement suggesting movement of sediment from one environment (early dune) to other environments including lagoon, beach, and strand plain.