Holocene Development of the Southeastern Texas Coast, Sabine Lake Area, from Foraminiferal Biofacies: ABSTRACT

Abstract

ABSTRACT Foraminifera were analyzed in cores of Holocene sediments from the southeastern Texas coast to better understand the post-glacial evolution of the Texas chenier plain and incised valley of the Sabine and Neches Rivers. Foraminifera are rare to absent in highstand interfluve marsh and in incised-valley fluvial floodplain deposits, whereas nearshore marine, estuarine, and chenier plain deposits contain abundant foraminifera. Overall foraminiferal diversity is low, and sample assemblages are dominated by Ammonia parkinsoniana and Elphidium gunteri. These species comprise about 78% of the fauna; the remaining taxa include Elphidium spp., miliolids, Brizalina spp., Bucella hannai, and Palmerinella palmerae. Samples are characterized by mixtures of well-preserved and poorly-preserved tests. This, along with the presence of Cretaceous foraminifera, suggests that many of the microfossils are reworked. Small adult foraminifera are common in cores from the chenier plain and are generally associated with fine-grained sediments deposited as mudflats between the sand-rich beach-ridges. Agglutinated foraminifera are surprisingly rare probably because geochemical conditions do not favor the preservation of agglutinated tests below about 2 m. Foraminiferal biofacies include a very low diversity, brackish (marsh) assemblage, a moderate diversity beach assemblage, a moderate diversity shallow marine assemblage, and a relatively high diversity, slightly deeper (but still nearshore) marine assemblage. These biofacies are consistent with those described from the Louisiana chenier plain. The faunal associations, diversity, abundance, and preservation provide insight to the paleoenvironments and depositional processes of the chenier plain.