290-6 Morphology vs. Sedimentology – the Quantitative Classification of Mixed-Energy Marginal-Marine Depositional Systems, Trinidad

Session: Delta Evolution from Rivers to the Shelf: Past, Present and Future Perspectives for Society

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Modern marginal-marine depositional systems along the Trinidad coastline were assessed and classified using quantitative to semi-quantitative classification methods. The primary objective was to elucidate the relationships between the mixed-energy processes acting along the present-day coastline, system morphology, and the associated sedimentary record. This study was conducted using a combination of Google Earth satellite images and shallow modern sediment cores. The morphology of the systems were mapped, and the areal extent of key depositional elements were quantified across several coastal depositional systems. This was then used to semi-quantitatively classify these mixed-energy systems. The shallow-sediment cores were logged, and the process distribution across the deposits were quantified using a process-probability approach. This provided a quantitative classification of process distribution across the sedimentary deposits, thus providing an avenue for comparison of geomorphological and sedimentological process-response across modern mixed-energy marginal-marine depositional systems.

The present-day Trinidad coastline is characterized by a combination of deltas, estuaries, tidal inlet complexes, strandplains and tidal flats. The spatial distribution is controlled primarily by the wave-regime, and to a lesser extent by tidal and fluvial processes. The wave regime changes from wave-dominated along the open east coast, to mixed-energy wave dominated along the semi-sheltered south coast, to mixed-energy tide dominated along the sheltered west coast. The morphology and qualitative classification of the systems noted along these coasts reflect these broad trends, however, there exists a disparity between the record of influencing and affecting processes on the morphology of the system relative to the sedimentary deposits. For example, the Moruga River delta has a quantitative morphological classification of W (62%), f (21%), t (17%) and a sedimentological classification of W (36%), t (33%), f (31%), two noticeably different process distributions.

The application of semiquantitative and quantitative classification methods on modern systems has shown their competence in classifying mixed-influence systems from their morphology and sedimentary record. Quantitative classification using depositional elements lends an appreciation to the morphological signatures of mixed-influenced systems. Quantitative classification for sedimentary sections gives an appreciation of the preservation of mixed influence physical processes. The integration of these approaches provides a robust framework for correlating physical processes with both morphological development and sedimentary deposits.

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

doi: 10.1130/abs/2025AM-9773

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