Ancient, pre-historic of Jamaica

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_{Trench on the east arm of the Morant River showing possible fault or a splay.}

The search for sites led to the Serge Island Dairy Farms, an abandoned pasture where a number of river terraces and risers were plain to see. The first trench was dug courtesy of the company who allowed us to use their backhoe for a day. Disappointed that the trenches dug on the farm revealed no relict fault processes, the team moved on to the east arm of the Morant River in the vicinity of the village of Hillside following a flyover of the fault from Morant Bay to Morant Point afforded us by the JDF air wing. Two trenches were dug at this locality using a rented backhoe across what appeared to be the trace or a splay (like a tributary is to a river) of the PGF. Samples of carbon and other sediments were sent for dating and obvious offsets of sediments were noted. Time constraints of team members precluded proper mapping and logging of the trench and trenching at other selected sites. All trenches were back filled with the material removed.

Trenching in Jamaica remains a study to be continued. What happens next will depend on the results of dating the samples collected, the availability of funds and time of the team members, particularly the palaeoseismologist. Other faults on the island worthy of investigation include the Duanvale, Crawle River, Wagwater, Silver Hill, Spur Tree, Santa Cruz and Montpelier faults. Currently, only 316 years of earthquake history for Jamaica is known and this holds just one earthquakes of magnitude greater than seven and two greater than six, not enough to forecast recurrence trends of these damaging events, and what the future might bring. Palaeoseismology could recover perhaps 1,000 years or 10,000 years of earthquake history which when combined with slip rates measured using Global Positioning System and knowledge of current seismicity could provide conclusive results regarding Jamaica's seismic past and future. Members of the team were in alphabetical order, Ms Bryn Benford (PhD student), Dr Charles DeMets (Geophysicist), Omar Josephs (Geologist), Will King (Geology student), Dr Paul Mann (Geologist), Dr Carol Prentice (Palaeoseismologist) and Dr Margaret Wiggins-Grandison (Seismologist).

Margaret D. Wiggins-Grandison, PhD, research fellow/seismologist

Address: Earthquake Unit, 2 Plymouth Crescent, University of the West Indies - Mona campus, Kingston 7

Telephone: (876) 927-2586/935-8249; fax: (876) 977-3575

email: margaret.wigginsgrandison@uwimona.edu.jm.

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