Migration of Neogene marine environments, southwestern Dominican Republic

Abstract

The Azua Basin contains a 4000-m-thick regressive Neogene sedimentary sequence that records the effects of neotectonic activity along the northern bounary of the Caribbean plate. Shifts of benthic foraminiferal depth zone boundaries between stratigraphic sections demonstrate a southeastward migration of paleoenvironments in the Miocene and early Pliocene which suggest that the Hispaniola restraining bend was activated near the beginning of the late Miocene. In the morthwestern part of the Azua basin, the boundary between the middle and upper bathyal biofacies is in the uppermost Miocene Globorotalia humerosa Zone; the bathyal-neritic boundary is near the top of the same zone. In contrast, toward the southeastern (i.e., seaward) end of the basin, the middle bathyal/upper bathyal boundary is just above the base of the lower Pliocene Globorotalia margaritae margaritae Subzone, and the bathyal-neritic transition falls within the upper part of the same zone or in the overlying Globorotalia margaritae evoluta Subzone. The diachroneity of biofacies boundaries spans a time interval of ca. 1 m.y. The foraminiferal trends are corroborated by the disposition of time-transgressive lithofacies.