Herrera
Sandstones in the Southern Basin Area, Trinidad: Evidence of Hyperpycnites Deposited Away From Ancient Oficina Delta Systems in Eastern
Venezuela
Gamero Díaz,
Helena1, Jo Reader2, Chris Izatt2, Carlos
Zavala3, Carmen C. Contreras F1 (1) Schlumberger
Venezuela, Caracas, Venezuela (2) BG Trinidad and Tobago, Port Of Spain,
Trinidad and Tobago (3) IADO-CONICET; Universidad Nacional
del Sur, Bahía Blanca,
Argentina
The Lower Miocene Herrera sandstones is a
prolific hydrocarbon producer in the Trinidad Southern Basin, and has
traditionally been interpreted as being deposited by a sand-rich turbidite fan system sourced from the north. Classical turbidite systems are related to surge-type turbidite flows originating from slope failures due to
shelf margin instability. Many authors have stated the existence of
controversial opinions concerning the origin of the Herrera sandstones, either
from the north, particularly the Central and Northern Ranges, indicating a southward
depositional direction, or whether the sands were derived from the west, that
is from Venezuela. Core and borehole
image descriptions show an abundance of bed load-, suspended load- and
lofting-related lithofacies suggesting an origin
related to a river-fed long-lived and quasi-steady turbidite
flow. The paleocurrent indicators interpreted from
borehole images show a paleotransport direction from Venezuela. Lignite material
indicates an ultimate source from a terrestrial deltaic environment, which
probably developed in Venezuela (Oficina
Formation). During the early Miocene, S-N oriented rivers draining the Guayana craton developed huge
delta systems in the coastal areas of the Eastern Venezuelan Basin. During humid climate
periods, high magnitude floods generated hyperpycnal
discharges from the flood-dominated river deltas that dramatically increased
the sediment flux into the Maturín and Southern Trinidad basins. An increasing
amount of data supports that hyperpycnal flows can
travel up to 1000 km basinward. Flows originating in Venezuela could thus travel to Trinidad as submarine (hyperpycnal) channels. This change in facies
models increases the exploration potential both in Trinidad and Venezuela basins.