Source-to-sink analysis of the lower Miocene strata in the Gulf of Mexico Basin
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The sedimentary archive of the Gulf of Mexico Basin provides an opportunity to study sediment routing from continental highlands to basin sinks for a large passive margin system. This dissertation focuses on the source-to-sink analysis of the lower Miocene system, a major siliciclastic unit. Much remains unknown about sediment routing within this system. In this work, detrital zircon U-Pb and (U-Th)/He double dating and channel-belt scaling relationship are used for source-to-sink analysis. Zircon U-Pb age data from 19 samples across the northern Gulf of Mexico margin indicate that continental-scale sediment sources shift across the northern Gulf of Mexico from highlands in western North America to the Appalachian Mountains and foreland basin in eastern North America during the early Miocene. Sediment associated with the paleo–Rio Bravo, Rio Grande, Brazos, Red, Mississippi, Tombigbee, and Apalachicola rivers can be differentiated, improving definition of sediment transport pathways from upland sources to basin sinks. Combined U-Pb and (U-Th)/He double dating on single zircon grains documents both crystallization and exhumation histories of source terranes and have the ability to differentiate first-cycle volcanic and plutonic zircons from multi-cycle zircons. Many Mesozoic zircons yield roughly identical U-Pb and (U-Th)/He ages, indicating that large volumes of sediments were eroded from various Cretaceous-Oligocene volcanic fields in western North America. A large proportion of older Proterozoic zircons, including those from Grenville, Mid-Continent and Yavapai-Mazatzal provinces, yield several phases of exhumation, providing clues for tracing intermediate sediment sources. This work shows that recycled sedimentary strata are important sediment contributors to the Gulf of Mexico Basin. We also estimate the drainage areas of lower Miocene systems by using scaling relationships, developed in source-to-sink studies, between drainage area and fluvial channel depth. Single-storey channel-belt thicknesses were measured from a well log database in this well-explored basin and used to estimate paleo-drainage areas of five differentiated early Miocene fluvial systems. The predicted drainage areas show good agreement with the paleo-drainage areas reconstructed independently from detrital zircon provenance analyses and continental geomorphic synthesis. Therefore, knowledge of fluvial deposit dimensions provides a first-order estimate of drainage basin area and a plausible assessment of a continental geomorphology.