Abstract
Detailed geologic mapping of the Fondo Negro-Sierra de Martin
Garcia
region of the Southwestern Dominican Republic establishes that
this
area
is part of a broad and diffuse Northern Caribbean plate boundary
zone
(PBZ).
Faulting in the study area is predominantly left lateral
strike-slip,
with
secondary compression (thrusting) causing both substantial, and
rapid,
uplift of the region. Folding associated with the wrench faulting
affects
rocks of all ages in the field area from Paleocene limestones to
Quaternary
alluvial fans.
New stratigraphic designations are proposed for mappable
litho-units
in the area, and these are correlated with Hispaniola stratigraphy
in
general
based on biostratigraphic age determinations. Thus a new formation
name,
the Fondo Negro Formation is proposed for a thick (2650 m.
exposed)
predominately
calcareous siltstone, marl and sandstone sequence which is exposed
between
the village of Fondo Negro and the Sierra de Martin Garcia where
it
lies
in tectonic contact with Paleocene to early Miocene carbonates.
The
Fondo
Negro Formation contains microfauna belonging to the Tortonian and
Messinian
intervals. The lowest exposed section of the Fondo Negro Formation
contains
distinctive, ridge forming, sandy limestones and this unit is
described
as the Gajo Largo member. The 400m. of predominantly grey
calcareous
shales
apparently conformably overlying the Fondo Negro Formation are
redefined
as the Bao Formation, also of Messinian age, and conformably above
that
the Pliocene, Arroyo Blanco Formation, also more specifically
defined
than
previous studies. The Arroyo Blanco Formation comprises sandy
marls,
and
resedimented carbonate shelf debris, as well as coarse sandstones
and
conglomerates.
In the east it is approximately 100m thick, and it varies as a
facies
transition
into evaporites in the northwest of the field area. The evaporite
faeies,
including massive pure gypsum beds are probably thicker than the
facies
in the east.
The carbonates of the Sierra de Martin Garcia were not mapped in
detail,
but paleontological determinations for samples collected indicate
a
broader
age range for the carbonates than suggested on existing maps
(Blesch,
1967),
from Paleocene to Early Miocene.
In addition to the primary field mapping, reconnaissance studies
and
paleontological analysis of samples from the Tavera Basin suggest
that
it is the earliest basin yet identified related to the initiation
of
the
northern Caribbean PBZ. That is that this basin can be related to
strike-slip
faulting in probably early Oligocene times and this represents
movement
along the Cayman Trough.
An interpretive cross-section across Hispaniola is presented which
suggests that present strike-slip activity is greatest in the
Cibao
Valley,
the Enriquillo Valley and in the northern, offshore areas of
Hispaniola,
and that the Island is cut by a great number of splay faults. The
mountain
ranges, the Sierra de Neiba and the Sierra de Bahoruco are
compressional
structures related to bends in the strike-slip fault system. An
attempt
is made to integrate this in the perspective of the Cainozoic
evolution
of the Greater Antilles.
Cooper, J.C., 1983. Geology of the Fondo Negro region, Dominican
Republic.
Unpublished MSc. thesis, State University of New York at Albany.
145pp.,
+xiv; 4 folded plates (maps)
University at Albany Science Library call number: SCIENCE
Oversize
(*) QE 40 Z899 1983 C66
MS thesis (scanned text pdf - 14.8 MB)
Plate 1 - Geological
map
of
the
Fondo Negro - Martin Garcia Region, Dominican Republic (west
part)
(uncoloured geological map;
scale
1:25,000) pdf file 3MB
Plate 1 - Geological
map
of
the
Fondo Negro - Martin Garcia Region, Dominican Republic (east
part)
(uncoloured geological map;
scale
1:25,000) pdf file 4MB
Plate 2 - Geological
cross
sections
of
the Fondo Negro Region (Dominican Republic)
(uncoloured; scale 1:25,000)
Plate 3 - Hispaniola
geological
cross
section
(uncoloured; scale
1:250,000)
Return to MS Theses completed in the
Geological
Sciences Program, University at Albany