Miocene tidal-influenced sedimentation to continental Pliocene sedimentation in the forebulge–backbulge depozones of the Beni–Mamore foreland Basin (northern Bolivia)

Abstract

Mio-Pliocene deposits of the forebulge–backbulge depozones of the Beni-Mamore foreland Basin indicate tidally to fluvially dominated sedimentation. Seven facies assemblages have been recognized: FAA–FAG. FAA represents a distal bottom lake assemblage, FAB and FAD are interpreted as tidal flat deposits, FAC and FAG are interpreted as fluvial systems, FAE sediments are deposited in a subtidal/shoreface setting, and FAG represents a meandering fluvial system. The identification of stratigraphic surfaces (SU, MFS, and MRS) and the relationship among the facies assemblages permit the characterization of several systems tracts: a falling-stage systems tract (FSST) followed by a lowstand systems tract (LST), a transgressive systems tract (TST), and a highstand systems tract (HST). The FSST and LST may have been controlled by the uplift of the Beni-Mamore forebulge, whereas TST may result from a quiescent stage in the forebulge. Subaerial unconformity two (SU2) records the passage from a tide-influenced depositional system to a fully continental depositional system. The Miocene tidal-influenced deposits in the Beni–Mamore Basin suggest that it experienced a connection, either with the South Atlantic Ocean or the Caribbean Sea or both.