A field guide to Barbados (Part 3): Northern Barbados
Stephen K Donovan (The Netherlands)
Stop 1: Arawak Cement Quarry
The area considered in this part of the guide is outlined in Donovan & Harper (2010, Fig. 1b) and Fig. 1. As with other articles in this series, the starting point is Bridgetown. Drive north from the Bridgetown area on Highway 1, the main west (or leeward) coast road, which is constructed on the Lower Coral Rock and overlies superficial deposits.
The First High Cliff and the Middle Coral Rock are close by in the east (Speed & Cheng, 2004). This coast has been developed for tourism and has neither the magnificent sea cliffs of the east coast, nor the impressive Atlantic breakers seen in the previous excursion. To the west, two submerged barrier reefs, at 22m and 70m water depth, are separated from the coast by a submerged wave cut terrace (MacIntyre, 1967). The shallower of these two reefs is still alive. To the north of Speightstown, Highway 1B turns inland at Littlegood Harbour, then north again near Colleton. In the Checker Hall area, in the parish of Lucy, take the left turn at the crossroads and proceed to the cement plant (approximately 59º 38’ 47” W 13º 17’ 6” N; Figs. 1 and 2).
The Arawak Cement Quarry was opened in 1984. It is situated close to the west coast (providing loading facilities for ships) and is the most important working quarry on the island. Permission from the owners is required if it is to be visited. Limestone from the quarry, mixed with clay from the village of Greenland, which is situated about 15km away, is used in the manufacture of cement on site (Gordon et al., 1986, pp. 123-125).
The limestones are well-lithified Lower Coral Rock of Late Pleistocene age. Large colonies of the scleractinian coral, Montastrea annularis (Ellis & Solander), are the main fossil component at this locality, some of which preserve borings. Extant M. annularis occurs in 2m to 40m water depth, although its optimum is 7m to 22m (Wood & Wood, 2000, p. 44) and is an important framework builder in Caribbean reefs (Woodley & Robinson, 1977, pp. 22-23). Sandier lithologies contain larger benthic foraminifera. Rare and unusual components of the fauna include the brachiopod, Argyrotheca barrettiana (Davidson) (Harper & Donovan, 2007), and the large heart urchin, Meoma ventricosa (Lamarck) (Donovan & Jones, 1994; Fig. 3).
The depth ranges for these two extant species are 60m to 172m (dead shells; live shells only known from 92m to 140m) and 2m to 200m, respectively (Asgaard & Stentoft, 1984; Hendler et al., 1995). The depth ranges of M. annularis and A. barrettiana obviously give different estimates of how deep the water was, perhaps suggesting that the limestones in this site represent a range of water depths.
Stop 2: Animal Flower Cave, North Point
Return to the main Highway 1B and continue north, then northeast through Broomfield and Content. Follow signs to the Animal Flower Cave, north of Flatfield.
The Animal Flower Cave (59º 36’ 50” W 13º 19’ 51” N; Figs. 1 and 4) is situated close to the most northerly point on Barbados. It is a public show-cave that has been visited by the curious since before the mid-nineteenth century. Access is provided by a staircase through a blowhole. The animal ‘flowers’ are live invertebrates, such as sea anemones and a tube-dwelling worm, the seafeather Sabellastarte magnifica (Shaw), which live in a rock pool (The Carpet Room) (Ali, 1996, pp. 222-223). The caves open onto the ocean and, being within the rugged cliffs of north Barbados, are the safest way to view the Atlantic. The caves are dissolved in the Middle Coral Rock and are floored by a distinctive surface within the limestones. That solution is still active, as indicated by the continuing growth of small stalactites.
Stop 3: Limestone cliffs
Walk along the cliffs to the west of North Point, until the wire fence of enclosed farmland is reached. This will provide dramatic views of the vertical cliffs of the Middle Coral Rock and the distinctive surface that floors the Animal Floor Cave is easily seen (Fig. 4), as are other caves, gullies and blow holes. Access to the cliffs is not possible due to their vertical, joint-controlled morphology – do not be tempted to try, even where there is an inviting bench formed by the bedding surface. Instead, examine the Pleistocene reef limestone that is abundantly exposed underfoot. The most prominent fossils in both the cliffs and on the cliff tops are colonial scleractinian corals.
Stop 4: Cluff’s Bay
Drive along the unpaved road nearest the coast, until the track to Cluffs Bay is reached on the right. Walk along this track to the bay. Care must be taken at this locality (approximately 59º 37’ 48” W 13º 19’ 38” N; Fig. 1), which is precipitously perched at the unconformity between the Miocene Oceanics and the basal Middle Coral Rock (Fig. 5).
This locality was described by Trechmann (1937, p. 344), who created a measured lithological section (Table 1).
|Unit no.||Lithology||Thickness (m)|
|3||Layers of lithothamnial limestone with clusters of small terebratulid brachiopods.||0.6 – 1.5|
|2||Beds of conglomerate made of clay-ironstone pebbles and other remanié debris mixed with pieces of Oceanic chalk, in places full of irregular worm tubules filled with marl. Haliotis, various bivalves, pteropods, etc.||1.5 – 3|
|1||Oceanics: Globigerina chalks with thin layers of brown material largely minute fragments of volcanic glass (base not seen).||9|
|Table 1. Schematic measured section of Trechmann (1937, p. 344); unconformity between units 1 and 2.|
Trechmann (1937, p. 349) listed a fauna of benthic molluscs, pteropods and brachiopods from this locality that is much less diverse than that from Whitehaven (=northwest side of Skeete’s Bay; see Donovan & Harper, 2010, Stop 2). In part, this may be the result of the easier access at the former locality. Perhaps, the most notable difference is the presence of three species of pteropods (free-swimming, pelagic sea snails) at Cluff’s Bay, a group that is rare at Whitehaven (Donovan and Harper, 2010). This possibly indicates a deeper water, more open marine setting at Cluff’s Bay. The large terebratulid brachiopod found at this locality is Tichosina inconstanta Harper & Donovan.
Ali, A. 1996. Barbados: Just Beyond Your Imagination. Hansib Caribbean, St. John’s, Antigua: 319 pp.
Asgaard, U. & Stentoft, N. 1984. Recent micromorphic brachiopods from Barbados: palaeoecological and evolutionary implications. Geobios Mémoire Spécial, 8: 29-37.
Donovan, S.K., including a joint contribution with Harper D.A.T. 2005. The geology of Barbados: a field guide. Caribbean Journal of Earth Science, 38 (for 2003): 21-33.
Donovan, S.K. & Harper, D.A.T. 2010. A field guide to Barbados: Part 2 – Coastal geology of southeast Barbados. Deposits, Issue 24: 28-33.
Donovan, S.K. & Jones, B. 1994. Pleistocene echinoids from Bermuda and Barbados. Proceedings of the Biological Society of Washington, 107: 109-113.
Gordon, M.J., Johnson, J.D., Payne, P.B. & Mottley, W. 1986. Modern cultural aspects of Barbados’s geology. In: 11th Caribbean Geological Congress Barbados — 1986. Field Guide, Barbados, July 1986: 105-125. Government Printing Department, Bridgetown, Barbados.
Harper, D.A.T. & Donovan, S.K. 2007. Fossil brachiopods from the Pleistocene of the Antilles. Scripta Geologica, 135: 213-239.
Hendler, G., Miller, J.E., Pawson, D.L. & Kier, P.M. 1995. Sea Stars, Sea Urchins and Allies: Echinoderms of Florida and the Caribbean. Smithsonian Institution Press, Washington, D.C.: xi+390 pp.
MacIntyre, I.G. 1967. Submerged coral reefs, west coast of Barbados, West Indies. Canadian Journal of Earth Sciences, 4: 461-474.
Poole, E.G. & Barker, L.H. 1983. The Geology of Barbados. 1:50,000 sheet. Directorate of Overseas Surveys and Government of Barbados, St. Michael.
Speed, R.C. & Cheng, H. 2004. Evolution of marine terraces and sea level in the last interglacial, Cave Hill, Barbados. Geological Society of America Bulletin, 116: 219-232.
Trechmann, C.T. 1937. The base and top of the coral-rock in Barbados. Geological Magazine, 74: 337-359.
Wood, E. & Wood, L. 2000. Reef Fishes Corals and Invertebrates of the Caribbean including Bermuda. New Holland Publishers, London: 144 pp.
Woodley, J.D. & Robinson, E. 1977. Third International Symposium on Coral Reefs. Field Guidebook to the Modern and Ancient Reefs of Jamaica. University of Miami, Florida: 33 pp.