Urban geology: The Worsley Park wall game, Manchester

Stephen K Donovan (The Netherlands) Wall games are a very geological form of light entertainment and education. I certainly have amused myself by identifying rocks and their features in walls since my days as an undergraduate and before. I was introduced to the name for the wall game (obvious, I know) by Eric Robinson (1996, 1997). Eric’s examples inspired me to devise my own version of a wall game in far-flung Jamaica. At the time, I was a member of the teaching staff in geology at the University of the West Indies in Mona, Kingston. Each semester, we took the first year classes for three one-day field excursions. As cash was getting ever tighter. I hit upon the money-saving idea of running one of the first trips on campus where there were various ‘urban geological’ features worthy of note. One of these was the stone base of a ruined building that had survived from Mona’s days as a sugar plantation. The rocks in the base were a marvellous mixture of blocks and rounded boulders, presumably collected from the bed of the nearby Hope River, which drains the mountainous country to the east of the university. This trip worked well and, after a few years, the late Trevor Jackson and I published a field guide based on my excursion (Donovan and Jackson, 2000). The primary criterion for a geologically interesting and educational wall game is a good variety of rocks. The Mona wall game was most satisfactory in this respect, with … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Jamaica’s geodiversity (Part 2): Highlights from the Neogene

Stephen K Donovan (The Netherlands) and Trevor A Jackson (Trinidad) This is the second and concluding part of our introduction to Jamaica’s geodiversity. Here, we are concerned with more Neogene ‘highlights’ dating from the Middle or Late Miocene, about 10mya, when the island became, once again, sub-aerially exposed. The glossary provided in Part 1, as well as the maps (Donovan & Jackson, 2012, figs 1 and 2), are also relevant to this article and first appearance of the relevant terms in the text are highlighted in bold italics. Highlights 1 to 5 were discussed in Part 1 and 6 to 12 are described below. Highlight 6. Wait-A-Bit Cave Jamaica is a land of caves and sinkholes (Fincham, 1977). About two thirds of the rocks exposed at the surface of the island are limestones, which are soluble in acidic groundwaters, that is, those that are more or less rich in dissolved CO2. The percolation of these waters ‘excavated’ extensive cave systems throughout Jamaica, mainly by dissolution, since the island was sub-aerially exposed about 10mya (Miller, 2004). Wait-a-Bit Cave, south of Green Town in the parish of Trelawny (Fig. 1), is unusual among these myriad caves for reasons apart from its euphonious name. Fig. 1. Cave survey and selected passage cross-sections (A-A’ to G-G’) of the Wait-a-Bit Cave, parish of Trelawny, Jamaica (after Miller & Donovan, 1996, text-fig. 2). The thick dashed line to the west of E’, and south of F’ and G’, marks the edge of the limestone overhang from … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Jamaica’s geodiversity (Part 1): Introduction and some older highlights (Cretaceous to Miocene)

Stephen K Donovan (The Netherlands) and Trevor A Jackson (Trinidad) With a length of only about 240km, Jamaica cannot be considered a large island. It is also relatively ‘young’ geologically, the oldest rocks being only about 140myrs old. This might sound old enough, but contrast it with, for example, rocks in the islands of the Scottish Outer Hebrides, which are about 2,000myrs old. But Jamaica is nevertheless noteworthy in having a rich diversity of rock types and geological features, and it is rightly known for its high biodiversity, both on land and in the surrounding seas. To give one example, the 500 or more species of extant land snails make Jamaica a biodiversity ‘hot spot’ for these familiar molluscs. However, Jamaica should similarly be recognised as a geodiversity hot spot, with a range of geological and physiographic features, strata and fossils that make it an unusually fruitful focus for earth sciences research. We could support our bold assertion by a detailed exposition with tabulation of principal features and comparison with similar-sized islands elsewhere, although such an approach would perhaps be better suited to a dry research journal. The potential for producing such a long, boring discursion is large and we intend to avoid the temptation to do so. Rather, we want to illustrate Jamaica’s geodiversity by reference to a dozen key features. These are available for inspection to anyone who is interested and which we will describe in two articles in Deposits. The choice of these features is personal – … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.

Jamaican fossil crabs

Stephen K Donovan (The Netherlands) and Joe SH Collins (UK) Decapod crustaceans (crabs) are among the most attractive of fossils. Yet, the beautifully preserved specimens seen in museum displays and dealers’ catalogues are in stark contrast with the usual haul of the collector, that is, scraps, commonly claws or (more rarely) bits of carapace, which we all find in (mainly) Cretaceous and Cenozoic sedimentary rocks. However, these bits and pieces represent most of the fossil record of crabs and, as such, are of importance to the systematist and anyone with an interest in aspects such as taphonomy and palaeoecology. Just as it is possible to identify a shark from a tooth or a cidaroid echinoid from a spine, so a crab claw can commonly provide data that permits its identification to the level of genus or species (Collins, 1999). The present authors, in collaboration with Roger Portell of the Florida Museum of Natural History at the University of Florida in Gainesville, have been collecting and studying the fossil crabs of Jamaica (and the wider Antilles) for over 20 years. Until the 1990s, reports of fossil crabs from the island were limited to a few fragmented specimens and rare, well-preserved carapaces (some retaining claws) or the isolated claws of mud shrimps (=Callianassa sensu lato), which were collected mainly from the Upper Cretaceous and Eocene by visiting geologists as an aside to their own research. They were sent to the British Museum (Natural History) for description. These early records were reviewed and … Read More

To access this post, you must purchase Annual subscription, 12 Month Subscription or Monthly subscription.