Some speculations on the Paleogene and Neogene tectonics of Jamaica

Abstract

Many neotectonic structures (<15 Ma) in Jamaica are best understood as reactivations (or inversion) of Paleogene structures (65–22 Ma). In the Paleocene, Jamaica underwent crustal extension which formed north‐northwest‐trending listric normal faults, including those of the Wagwater Belt which occupied a half‐graben formed over the northeast‐dipping Wagwater Fault. From the Middle Eocene (45 Ma) to Late Oligocene (23 Ma), further subsidence (possibly thermally induced following lithospheric thinning) resulted in the accumulation of a carbonate bank. Beginning in the Early to Middle Miocene, the tectonic regime changed to one of active east–west‐trending, left‐lateral, strike‐slip motion that persists to the present day. New east–west‐trending faults formed during this phase, but secondary northeast–southwest shortening produced in this regime reactivated many of the older, Paleogene north‐northwest‐trending structures. In eastern Jamaica, oblique thrust motion is concentrated on the Wagwater Fault, tectonically inverting the Wagwater Belt. The Long Mountain anticline may be a fault propagation fold over a thrust that branched from the main Wagwater Fault surface. Motion on the Silver Hill Plantain Garden Fault system resulted in the northward rotation of the Blue Mountain Block around an approximately horizontal axis and revealing the upper crustal structure of eastern Jamaica. In the central part of Jamaica, north‐northwest‐trending faults divide the terrane into a series of blocks. Evidence of right‐lateral, horizontal‐slip on some of the faults and palaeomagnetic results may suggest a domino‐style, anticlockwise rotation around vertical axis by about 10°. Copyright © 2008 John Wiley & Sons, Ltd.

Protolith provenance and thermotectonic history of metamorphic rocks in eastern Jamaica: Evolution of a transform plate boundary

“…Thus, stratigraphic relationships indicate that the Westphalia Schist was exposed at the surface some time before 62-65 Ma, hence before the 39 Ar/ 40 Ar ages for Westphalia Schist, but more recently than the K-Ar age (78 Ma; Lewis et al, 1973, corrected) for hornblende in Westphalia Schist. Subsequently, the Westphalia Schist was buried rapidly beneath the Wagwater Group (Draper, 1987(Draper, , 1998(Draper, , 2008Robinson, 1995;Mann and Burke, 1990). This suggests that our new Westphalia 39 Ar/ 40 Ar ages and the previously published K-Ar biotite ages are associated with heating during deposition of the Wagwater Group.…”

“…for a rate of exhumation of ~1.3 mm/yr. Previous workers (Robinson, 1995;Draper, 1998Draper, , 2008Mann and Burke, 1990) interpreted the thick (>6.8 km) Paleocene to Eocene Wagwater Group as having been deposited in a rapidly subsiding, normal fault-bounded basin. Burial metamorphism with temperatures attaining ~300 °C was responsible for resetting the lowtemperature argon systems (K-feldspar, biotite, whole rock) in the Westphalia Schist at ca.…”

“…The Wagwater Group contains Paleocene to Middle Eocene volcanic rocks and siliciclastic fl ysch, interpreted as having been deposited in a transtensional rift basin (Robinson, 1994;Draper, 1998Draper, , 2008Mann and Burke, 1990). The Wagwater Group consists predominantly of two formations, the Wagwater Formation and the Richmond Formation.…”

“…The geologic history of the rocks exposed on the island can be summarized in four tectonic stages (Draper, 1998(Draper, , 2008Robinson, 1994): (1) Early Cretaceous-Early Paleocene island arc, CLIP, and convergent plate boundary tectonics.…”

“…In eastern Jamaica, the Plantain Garden fault turns to the north, producing a restraining bend (Mann et al, 1985(Mann et al, , 2007 (Fig. 1A), which over the past 10-15 million years has been responsible for the uplift of Cretaceous igneous and metamorphic rocks in the Blue Mountain Inlier (Draper, 2008).…”