44 Environmental Geoscience (Posters)

Wednesday, 11 March 2026
9:00 AM - 12:00 PM
RCC, Lower Level Hall

A review of mineralogic, geochemical, and environmental properties of selected coastal sands from multiple regions in northern and western Puerto Rico, USA.

Paper number: 44-7
Program: Technical Sessions
Time: 9:00 AM – 9:00 AM

Authors

Abstract

Sands from coastal environments in Puerto Rico (PR) are comparatively understudied relative to other areas globally. Constraints on sand mineralogy and geochemistry provide insight into the geology of a region, for mineral exploration, geotechnical uses, and understanding the geogenic background of pollution for any given area. Presented here are data sets from our recent investigations of various scales using powder X-ray diffraction (XRD), high-resolution inductively coupled plasma-mass spectrometry, and scanning electron microscopy (SEM). Sands from a site near Guanajibo in western PR are strongly influenced by ultramafic rocks and have abundant serpentine, oxides, and altered olivine and pyroxenes. These sands are characterized by comparatively high concentrations of siderophile metals (e.g., Ni, Cr, Co). Results invite questions regarding the broader distribution of these sands, coastal aquifer relationships, geogenic background, and exposure in the area. Carbonate coastal sands from tourist regions in southwestern PR have high porosity, are dominated by a mix of aragonite, calcite, and high-Mg calcite, have generally low metal content, and may show promise for emergency only geotechnical applications, such as constructed wetlands, considering a functional ban on mining in PR, and need to preserve beach environments. Examples of sands from northern PR coastal settings are distinct from other regions and are dominated by quartz, feldspars, and minor biogenic carbonates and lithics. Some northern sands have appreciable arsenic (As) concentrations and raise concerns regarding coastal aquifers, the form and mobilization of As in coastal aquifers, and broader long-term geohealth questions. Both macroplastics and microplastics have been observed in multiple settings. Macroplastics observed can likely be detected and readily distinguished from sand substrates using image spectroscopy techniques. Microplastics are commonly observed in samples, appear to be variable in nature, and are an important and evolving component of the study. Results provide new constraints on regional mineralogical and geochemical diversity and help define the geogenic background for future pollution studies.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1

doi: 10.1130/abs/2026SE-411632

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