Caribbean Journal of Earth Science Volume 35 (2001)

Editor: Simon F. Mitchell

 


 

Pleistocene echinoids from Tobago, West Indies

S. K. Donovan, D. N. Lewis, H.Vincent and I. M. Blackman

Abstract – The late Pleistocene (Sangamonian) coral limestone of Tobago, West Indies, has yielded three species of regular echinoid, Eucidaris tribuloides (Lamarck), Astropyga magnifica A. H. Clark and Lytechinus variegatus (Lamarck). Of these, only L. variegatus is known from tests; all species are still extant and common in Antillean, shallow-water environments. Spines of E. tribuloides and diadematids are a common component of late Cenozoic, shallow water assemblages in the Antillean region. External morphology is sufficient to differentiate E. tribuloides from the only other member of this genus in the late Cenozoic of the region, E. madrugensis (Sánchez Roig). Fossil diadematid fragments have hitherto been left in open nomenclature, but comparison of the Tobago specimen with primary spines from extant Antillean species has shown it to be A. magnifica. The fossil tests of L. variegatus from Tobago are small, probably a contributory factor in their preservation, although presenting problems for identification when compared with larger, more mature individuals with a more abundant tuberculation. Both tests of this species were encrusted by calcareous algae, which may have further aided in fossilization. This ‘assemblage’ of echinoids suggests that the late Pleistocene reef limestones of Tobago were deposited in 11-50 m of water. Caribbean Journal of Earth Science Volume 35(2000), 1-12


Late Quaternary Geology of the Eastern Pedro Bank

R. Maharaj


Abstract – A limestone consisting of cross-bedded oolitic grainstone with abundant root traces crops out over 400 km2 of the south-eastern portion of the Pedro Bank and is herein formally named the Portland Rock Formation. The large-scale cross-bedding is interpreted to be due to aeolian dune migration, while surfaces with root traces are interpreted as palaeosols and indicate that the dunes were periodically stabilized by vascular plants. A radiocarbon age of 32.04 kyr (+3.2/-2.28 kyr) on a single whole rock sample from this formation is interpreted to be a composite age reflecting the ages of the nuclei, oolitic laminae and vadose zone cement. Since the cement volume is relatively insignificant, this gives an approximate age for the formation of the sediment and a maximum age for the formation of the dunes. The Portland Rock Formation therefore represents the largest last-glacial palaeodune field in the northern Caribbean. Caribbean Journal of Earth Science Volume 35(2000), 13-17.


Lithostratigraphy of the Late Cretaceous to ?Paleocene succession in the western part of the Central Inlier of Jamaica

S. F. Mitchell and D. Blissett

 

Abstract – The lithostratigraphy of the Late Cretaceous to ?Paleocene rocks in the central and western parts of the Central Inlier (Jamaica) is formally described based on detailed geological mapping of the inlier. Seven formations are recognised: Slippery Rock Formation; Thomas River Formation (new formation); Guinea Corn Formation; Green River Formation (new formation); Peckham Formation (new formation); Mahoe River Formation (new formation); and Waterworks Formation (new formation). The latter four formations comprise the Summerfield Group. Type sections for each formation are described. Caribbean Journal of Earth Science Volume 35(2000), 19-31


First record of the holectypoid echinoid Echinoneus cyclostomus Leske from the late Pleistocene Falmouth Formation of Jamaica

G. Simpson

Abstract. The irregular echinoid Echinoneus cyclostomus Leske is reported from the late Pleistocene shallow marine Falmouth Formation, West Rio Bueno, Jamaica. The species has been reported from the deeper water shelf marlstones of the early Pleistocene Manchioneal Formation of eastern Jamaica, the Miocene horizon of Anguilla and the ?Miocene La Cruz marl of Cuba. Caribbean Journal of Earth Science Volume 35(2000), 33-36.


A new type of Holocene deposit in Cuba: “trapped” insects within stalagmitic calcium carbonate

S. Diaz-Franco and R. Rojas-Consuegra

Abstract. A newly found fossiliferous site in Cuba contains small complete insect bodies (Coleoptera) embedded in stalagmitic calcium carbonate. The insects were trapped on the wet surfaces of stalagmites and coated in deposits of calcium carbonate.Caribbean Journal of Earth Science Volume 35(2000), 37-38.


© Geological Society of Jamaica, 2001.