Using orthographic projection with geographic information system (GIS) data to constrain the kinematics the Central Range Fault zone, Trinidad

Fold geometry versus axis orientation can be used to constrain the kinematics of transpressional plate boundaries. This approach is typically based on bedding orientation data collected in the field, however, in some regions outcrop quality is insufficient to provide enough measurements. We extract orientation data from a georeferenced geologic map and a digital elevation model and to constrain the kinematics of a poorly exposed, active transpressional boundary: the Central Range Fault zone in Trinidad. Strike-and-dip orientations are calculated based on contact positions extracted from the digital geologic and topographic datasets. The uncertainties in the both horizontal position and elevation of the contact are propagated into the final kinematic analysis. Analysis of folds adjacent to the Central Range Fault suggests the angle of oblique convergence in transpression (α) varies from 20° to 85°. The majority of folds, however, are consistent with a large component of contraction (i.e. α > 50°). The analysis also suggests folding in the Central Range records a minimum of 3–9 km of contraction, 3 km of strike-slip motion, and 4–9 km of total plate motion. The range of values reflects uncertainties in the position of the folded contacts. We interpret the overall kinematics of deformation, amount of shortening, and homogeneity of the finite strain field to indicate that active deformation on the Central Range Fault zone has not yet accumulated enough strain to overprint the effects of earlier (pre-strike-slip; pre-Middle Miocene) fold-and-thrust style tectonics.

► Fold geometries are modeled from map patterns using digital map data in ArcGIS.
► Modeled fold shapes are used to calculate strain and kinematics in a transpressional fault zone.
► Uncertainties in the geologic map and elevation datasets are propagated into the strain and kinematic calculations.
► Central Range Fault zone borderlands have accommodated a minimum of 4–9 km of plate motion.