107-18 Investigating the Provenance of Mixed Carbonate-Siliciclastic-Volcaniclastic Conglomerate Facies in Curaçao’s Pocket Beaches and Implications for Their Occurrence in Late Pleistocene Limestone Terraces.

Session: Sedimentary Geology Division/SEPM Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation

Presenting Author:

Authors:

Abstract:

Above the Upper Cretaceous Curaçao Lava Formation (CLF), four siliciclastic rock formations are recognized on the island of Curaçao (in the southern Caribbean). The youngest are the Eocene, Neogene, and Quaternary limestone formations that are exposed in bluffs and terraces that ring the island. Eroded into these terraces on both the windward and leeward sides of the island are pocket beaches or “bokas” that are connected to dry stream beds called “rooi” or arroyos. These beaches contain an array of sediment clasts whose provenance is not well understood nor are the conditions responsible for their transport and deposition to these pocket beaches understood. Some clasts are obviously derived from erosion and weathering of the adjacent limestone and dolostone (i.e. Seroe Domi Formation) terraces, as well as from modern offshore reefs. Other clasts are derived from much older rock formations found in the interior of the island. The CLF consists of mafic volcanic rocks including pillow and picrite basalts, hyaloclastites, dolerites, and interbedded cherts and marls. Thus the “modern” beach clast assemblage spans more than 65 million years and have a complex depositional history impacted by diverse transport histories, as well as climatic and sea level conditions that are not well understood given modern environmental conditions.

As such, this study investigates sedimentological characteristics regarding the provenance of unlithified polymictic beach sediments as well as Pleistocene-aged carbonate-cemented conglomerates found along the coast of Curaçao. Sediments from Playa Santu Pretu, a small pocket beach along the western coast, among others, have been analyzed to determine differences in composition, color, angularity, sphericity, etc. A stratigraphic assessment was also conducted to provide insight into sediment transport and deposition during the Pleistocene. Sediment samples were collected and analyzed for their grain size distributions as well as microscopic examination. Geolocated and scaled photographs were taken and clast angularity and sphericity were assessed using ImageJ software that enabled measurement of individual clasts. Hjulström’s diagram has been employed to understand sediment assemblage characteristics relative to hydrodynamic transport histories of both sediments and lithified rock units. Findings allow a deeper understanding of the sedimentation on Curaçao and offer new insights into implications for determining the significance of polymictic conglomerates for the evolution of coastal geomorphology in carbonate-rich tropical systems in the southern Caribbean.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9595

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.