11 Structural Geology (Posters)

Sunday, 19 March 2017
8:00 AM - 12:00 PM
Urban, 17th Floor

STRUCTURAL ANALYSES OF OVERTURNED AND SHEARED ROCKS IN THE CARIBBEAN OROGEN HINTERLAND: KINEMATICS OF FAULTS AND SCALY FABRICS IN THE GALERA GRIT AND TOCO CATACLASITE, TOCO, TRINIDAD

Paper number: 11-4
Program: Technical Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The Galera Grit is a white, coarse-grained, competent, but faulted, meta-sandstone that outcrops near Toco in NE Trinidad that has been completely overturned. The Galera Grit sits on top of an intensely deformed, less competent, meta-mudstone/-sandstone/-limestone unit that we call the Toco Cataclasite. A previously proposed tectonic model for NE Trinidad is not based on robust field observations and structural analyses. To create a better-supported tectonic model for the overturning/emplacement of the Galera Grit and creation of scaly fabrics in the Toco Cataclasite (~melange), we are performing field-based kinematic analyses on the faults (D3), folds (D2), and scaly fabrics (D1) in these two units. We have grouped and inverted our preliminary Galera Grit fault-slip data and determined pressure (P) and tension (T) axes. Preliminary results show normal faults with multiple orientations, indicating that stretching (T) in multiple horizontal directions predominated in the Galera Grit “cap”. We hypothesize that D3 multidirectional “spreading" took place after the Galera Grit was emplaced over the Toco Cataclasite by low-angle, layer-parallel shearing and faulting. We will next study Toco Cataclasite scaly fabrics in the field, specifically using the orientations of long axes phacoids and P-Y shear intersections and obtain D1 (emplacement) shear-sense directions.

Geological Society of America Abstracts with Programs. Vol. 49, No. 2

doi: 10.1130/abs/2017NE-291133

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