Sand-size sediments are contributed to the northern Gulf of Mexico by a large number of streams and, to a lesser extent, by marine erosion of coastal deposits, mainly of Pleistocene age. The heavy mineral assemblages and distributive provinces of most sources can be recognized in the Holocene sediments of the northern Gulf of Mexico. Five heavy mineral provinces have been established, the eastern Gulf, Mississippi, western Gulf, Texas coast, and Rio Grande provinces. The western Gulf province is of complex origin and consists of sediments deposited on the continental shelf during the early Holocene rise in sea level by the Mississippi, Rio Grande, Colorado, Brazos, and Trinity-Neches rivers. The changing pattern of alluvial plains, deltas, shore deposits, and several major changes in the direction of longshore drift and currents during the transgression can be recognized. The Texas Coast province consists of a mixture of material contributed by the rivers of the area and of detritus eroded from the Pleistocene deposits of the area by waves. Longshore drift to the W. is an agent in the distribution of sediments derived from the Colorado River in the zone between Galveston Bay and Aransas Pass. This material enters the bays from the Gulf side. Barrier island and bay sands are of local origin W. of Aransas Pass and consist of a mixture of material derived from the Pleistocene on the land side and material brought in from the shelf during and after the transgression.

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