Two field trips were organized in 1984 to view exposures in the western Central Range and SanFernando area. The first was held on Saturday, 7th April, and visited the following stops which are numbered in squares on Figs. 1 and 2.

RAVINIE SABLE

A large quarry provided an excellent overview of the Sum Sum Sands which were also examined in detail at the working faces. At the latter, stacked planar crossbed-sets typical of the sands, and some thicker homogeneous beds, one of which had good examples of penecontemporaneous deformation structures, were seen. Deposition by braided streams was postulated for the origin of the sands.

Prior to leaving the quarry, attention was drawn to colour variation exhibited by the sands and which is believed to be caused by response of their high iron content to weathering.

DURHAM SAND, DURHAM HILLS ROAD

From the geological map of Trinidad it may be seen that the older Durham Sand is not as continuous as the Sum Sum. However, the exposures seen at stop 2 indicate a similar environment of deposition and show the sand to be alike overall.

(3) BRASSO AND MANZANILLA FORMATIONS, BRASSO VILLAGE AREA

Several stops were made to examine the beds exposed in the Brasso River near and in the Brasso Gorge. Exposures of the Brasso Formation showed it to be a dark blue-grey, calcareous clay with abundant molluscan fossils and debris. It is a good example of shelfal deposition. The clays exposed here belong to the Globorotalia fohsi fohsi zone of Middle Miocene age.

Within the Brasso Gorge itself, the next stop attempted to show the faulted nature of the Manzanilla/Brasso contact before the party moved downstream (north) to the well-exposed 'reefs' of the Montserrat Glauconitic Sandstone in the river bed. This, the middle member of the Manzanilla Formation, is in reality, a bioclastic, glauconitic limestone with sand-size clay clasts and larger bryozoan, mollusc and echinoid fragments and fossils.

Well-developed potholes caused by current scouring are common in the 'reefs'.

Further downstream exposures of the Telemaque Sandstone with associated coals were seen.

After leaving the river, a brief stop was made at the junction of the Brasso-Flanagin Town and Grand Couva Roads to view a calcareous sandstone lens developed in the Telemaque sandstone and previously worked in the nearby Brasso Quarry. This exposure enables one to see the abundant but poorly preserved remains of the gastropod Turritella altilira montserrateus which is typical of the lens.
(4) GUARACARA LIMESTONE, TRINIDAD CEMENT CO. MAYO QUARRY

Mr. James of the Trinidad Cement Company, provided an excellent tour of the Quarry, showing how the CaCO3 content of the limestone varies in different areas. The limestone was shown to be mainly reefal debris with a high calcareous clay content. Extensive calcite veining and crystals in crags are seen in some areas.
(5) POINTE-A-PIERRE FORMATION, SAND ROAD

The final stop was at the sands of Pointe-a-Pierre Formation exposed at the concrete products factory at Sand Road, Poonah. This provided members who were familiar with the Chalky Mount Member of the Scotland Formation in Barbados to compare it with the quartzose grits of this exposure which is of a similar age.
The G.S.T.T. wishes to thank the owners for permission to enter their Quarries and those members of their staff who assisted on the trip.

The second field trip, organised to view exposures in the San Fernando area, was held on 1984 Sunday 16th September (Stops numbered in circles on Figs. 1 & 2). The localities for this trip were selected to include Outcrops of Cretaceous and Tertiary age and to provide an opportunity to examine their structural setting.

(1)
SUM SUM QUARRY - CEDAR HILL ROAD

The Sum Sum sands occur within the Talparo Formation and are of Pleistocene age. The Talparo Formation is restricted to the Northern (Caroni) Basin, outcropping over a wide belt from the west to the east coast on the northern flank of the Central Range Uplift.

The massive bedded Sum Sum sands are friable clear to light grey in colour, containing 75% quartz, and are interbedded with clay and lignites. These well-sorted Sum Sum sands are excellent aquifers.
(2) SPRINGVALE QUARRY - FORRES PARK

The Springvale Formation (Upper Pliocene) takes its name from the Springvale Quarry (Springvale Estate, near Forres Park) northeast of Pointe-a-Pierre, where it contains a spectacular well-preserved megafauna. The quarry is situated approximately 1 mile north of the NE/SW trending Warm Springs fault which it has been suggested is a major right-lateral wrench fault.
The Springvale Formation outcrops all along the