A PRELIMINARY TECTONOSTRATIGRAPHIC FRAMEWORK FOR ONSHORE TRINIDAD
C.C. WIELCHOWSKY
V.D. RAHMANIAN
J. HARDENBOL
Exxon Company, International, Houston,
Texas 77001, U.S.A.
Preliminary analysis of data collected from 60 field localities, combined with limited well, seismic, and published
data, indicates that the tectonostratigraphic history of onshore Trinidad can be divided into four broad developmental
phases. These are as follows:
1). a Middle Jurassic through Late Cretaceous rift/passive-margin sag phase related to the creation of proto-Caribbean
oceanic crust with sediments in central and southern Trinidad being sourced from terrains to the south' or southwest'
underlain by South American crust. Apparent stratigraphic and structural continuity between eastern Venezuela and
Trinidad, and lateral persistence of large-scale gravity anomalies are used to suggest that the greatly shortened
Jurassic-Cretaceous terrains- of most central and southern Trinidad are neither wildly allochthonous (i.e., hundreds
of km of lateral translation) nor significantly rotated, however, because Trinidad is situated within a 150-250
km-wide plate -boundary zone that has accommodated significant Cenozoic transform motion, major translations and
rotations south of the El Pilar Fault System cannot be ruled out.
Terrains north of the El Pilar are almost, undoubtedly, relatively far traveled. For example, preliminary 4OAr/39Ar
incremental release and standard K/Ar radiometric age date indicate that the Jurassic-Cretaceous rocks of the Northern
Ranges were dynamothermally metamorphosed by the end of the Cretaceous. Because the older strata of central and
southern Trinidad show no strong evidence of major nearby Cretaceous tectonism, it is reasonable to assume that
rocks of the Northern Ranges were deformed at some unknown distance west or northwest of Trinidad, and subsequently
translated into their present position.
2) a latest Cretaceous through mid-Early Miocene episodic transpressional phase possibly related to the formation
of proto-Caribbean transform / incipient arc system in front of an east-facing, proto-Antilles Arc System. The
deformational scheme of Trinidad, was probably one of basement-involved strike slip and oblique subduction of continental
and/ or oceanic lithosphere to the north and generally detached thrusting and folding to the south Sedimentary
polarity reversed at this time with the development of a rising tectonic terrain to the north' or northwest'. Thick
shale sequences and fairly thin shallow and deep-water sands were deposited in the foreland troughs formed by this
event. These sub-basins were characterized by narrow shelves and rapid lateral facies changes. Greatly different
strengths and ductilities give rise to structural disharmony between the Jurassic-Cretaceous and Paleocene-Miocene
units.
3) a mid-Early Miocene to late Middle Miocene extensional phase probably related to large-scale transtension as
Trinidad moved past the lesser Antilles arc. Sediments were derived from both the north' or northwest' and south
or southwest' as the Caroni and Tobago basins were formed. This phase may or may nor have affected rocks south
of the Caroni basin.
4) a late Middle Miocene to present transpressional phase with local transtension that emplaced and uplifted the
Northern Ranges, inverted the southern edge of the Caroni basin, and shortened the sedimentary sequences of central
and southern Trinidad. Stratal shortening from the Central Ranges to the south coast of Trinidad exceeds 11km,
while basement-related strain of unknown magnitude is taken up along major oblique-slip fault systems. Deltaic
sediments of this filled the Caroni, Southern, and Columbus basins.
Relative to present day coordinates (i.e., no rotational effects are considered).
Home | About Us | Links To The World | Publications | Upcoming Events |
Feedback | Executive Members | Geology |Teaching Resources| Virtual Field Trip
THE GEOLOGICAL SOCIETY
OF TRINIDAD & TOBAGO
P.O. Box 3524, La Romain, Republic of Trinidad and Tobago, W.I.