RAISED SHORE PLATFORMS AND AN EARLY JAMAICAN POTSHERD IN SOUTHWESTERN ST. ELIZABETH PARISH: NEOTECTONIC IMPLICATIONS FOR AN ARCHAEOLOGICAL HYPOTHESIS

Raised shore platforms along the southwestern coast of Jamaica were developed on coastal exposures of the Newport Formation (mid-Eocene to mid-Miocene) and overlying Falmouth Formation (late Pleistocene). The Newport Formation is mostly lime mudstone to wackestone. It was fractured, faulted, and relict topography is exposed below the disconformity that marks the base of the Falmouth Formation. The Falmouth Formation is a cliff-forming unit between Black Spring Point and Frenchman's Bay (~3 km); it contains in situ corals at its base overlain by calcareous sandstone and various coral facies. The Falmouth is associated with the MIS 5e.

Shore platforms developed adjacent to the disconformity and subsequently were encrusted by serpulid worms. Encrustations are approximately 3 – 4 cm thick, forming biostrome-like worm reefs on the beveled platforms. Serpulid worms typically live in marine settings, ranging from near sea level to great depth. Encrusted raised shore platforms are now approximately 1.0-meter above sea level and a prominent wave-cut notch is located on the seaward margin of the platforms. We interpret uplift as a result of vertical fault movements on the Pondside Fault which parallels the coastline from Wally Wash Pond to Fort Charles. A calibrated standard carbon-14 age of 888 ± 122 cal CE was obtained on the serpulid material from near Black Spring Point. A second sample yielded an AMS C-14 age-date of 1296 ± 62 cal CE. Additional dates are needed but preliminary ages indicate late Holocene uplift of the platforms.

Recently, a 10-cm potsherd, provisionally identified as Jamaican redware, was found cemented to an exposure of the Newport Formation in front of a raised shore platform. Redware people were beach dwellers, and archaeological sites in Jamaica are clustered in southwestern Jamaica. Their sites are associated with thin middens that show a scattered or halo-like distribution of artifacts. Redware culture spanned 600 – 900 CE, partly overlapping with one of the carbon-14 age-dates of serpulid material. The succeeding Meillicoid culture lived in upland areas and were early agriculturalists. The implication of a 1.0 m x 3.0 km rupture is that it potentially occurred during a 6–7 M earthquake that raised the shoreline and may have generated a tsunami that led to a cultural transition from redware to Meillicoid.