Presentation Title

Using X-ray diffraction of stream sediment to better understand the geology and weathering environment of central Cuba

Abstract

In humid, tropical regions, where chemical weathering rates are high, the relationship between bedrock composition, stream sediment mineralogy, and stream water chemistry is neither straightforward nor well known. For a country such as Cuba, which has been isolated from much of the world’s geologic community for decades, data are sparse; yet, such data are important for understanding landscape change over time, including deciphering trends in stream water geochemistry and rates of erosion, both natural and human caused, particularly changes catalyzed by agriculture. Here, as part of a collaborative Cuban-American project focused on understanding mass transfer from the island to the ocean, we use quantitative X-ray diffraction to determine the bulk mineral composition of river sediments and their relationship to water chemistry, land-use, sediment elemental composition, and mapped bedrock geology in 25 central Cuban drainage basins.

Diffraction data show that quartz, feldspar, and calcite are present in most stream sediment samples reflecting the relative abundance of igneous, metamorphic, and carbonate lithologies in central Cuba. Quartz is the most abundant mineral. Amphiboles, swelling clays, and micas are also common. Although quartz dominated stream sediment across all sampled watersheds, significant amounts of calcite suggest that the mineralogy of the stream sediments is useful both as a marker for watershed geologic characteristics and as a proxy for weathering intensity. We find that, in combination with other data, such as water chemistry and cosmogenically-determined erosion rates, mineralogical analysis can be used to determine the lithologic influence on local sediment and river water composition in each watershed.

Primary Faculty Mentor Name

Paul R Bierman

Secondary Mentor NetID

jmhughes

Secondary Mentor Name

John M Hughes

Status

Undergraduate

Student College

College of Agriculture and Life Sciences

Program/Major

Geology

Primary Research Category

Engineering & Physical Sciences

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Using X-ray diffraction of stream sediment to better understand the geology and weathering environment of central Cuba

In humid, tropical regions, where chemical weathering rates are high, the relationship between bedrock composition, stream sediment mineralogy, and stream water chemistry is neither straightforward nor well known. For a country such as Cuba, which has been isolated from much of the world’s geologic community for decades, data are sparse; yet, such data are important for understanding landscape change over time, including deciphering trends in stream water geochemistry and rates of erosion, both natural and human caused, particularly changes catalyzed by agriculture. Here, as part of a collaborative Cuban-American project focused on understanding mass transfer from the island to the ocean, we use quantitative X-ray diffraction to determine the bulk mineral composition of river sediments and their relationship to water chemistry, land-use, sediment elemental composition, and mapped bedrock geology in 25 central Cuban drainage basins.

Diffraction data show that quartz, feldspar, and calcite are present in most stream sediment samples reflecting the relative abundance of igneous, metamorphic, and carbonate lithologies in central Cuba. Quartz is the most abundant mineral. Amphiboles, swelling clays, and micas are also common. Although quartz dominated stream sediment across all sampled watersheds, significant amounts of calcite suggest that the mineralogy of the stream sediments is useful both as a marker for watershed geologic characteristics and as a proxy for weathering intensity. We find that, in combination with other data, such as water chemistry and cosmogenically-determined erosion rates, mineralogical analysis can be used to determine the lithologic influence on local sediment and river water composition in each watershed.