There Is No Goodfacies Characteristic to This

December 2004 Cainozoic Research, 3(1-2), pp. 5-29, In'. Donovan, S.K. (ed.). The Mid-Cainozoic WhiteLimestone Group ofJamaica Lithostratigraphy and palaeogeography of the White Limestone Group Simon+F. Mitchell Department ofGeography and Geology, University ofthe West Indies, Mona, Kingston 7, Jamaica; e-mail: [email protected] Received 3 December 2001; revised version accepted 14 April 2003 divided six formations.The formations The White LimestoneGroupof Jamaica is into Troy, Swanswick, Somerset and Moneague were that the stable Clarendon the and Pelleu Island formations deposited on a carbonate platform developed on Block; Montpelier were this The formations characterised the - deposited in the deep-watertroughs adjacent to platform. are by following lithologies: Troy - - grey and pink, micritic limestones, dolomicrites and sucrose-dolostones; Swanswick white, foraminiferalgrainstones; Somerset grey and pink, foraminiferaland algal packstones; Moneague - white grainstones, packstones and wackestones; Montpelier - chalks with chert bands; Pelleu Island - chalks lacking chert bands. The Ipswich Formation is transferredto the Yellow Limestone Group. In the late Middle the Clarendon Block had rim of foraminiferal tidal-flatdominated Eocene, a grainstones surrounding a restricted, platform. In the Late Eocene the platform was flooded to greater depth and packstones spread across the northernhalf. In the Oligocene, the dominated facies that inward restricted interior platform margin was occupied by a grainy Lepidocyclina- marginal passed into a marine with diverse of miliolidforaminifera. Similar facies into the WhiteLimestone assemblages patterns persisted Miocene, although any ofthis age that was deposited has been eroded from the northern halfofthe platform. During the late Middle Eocene to Middle Miocene, in the deep-water troughs adjacent to the platform, chalks accumulated together with coarse-grained detritus (calcarenitic turbiditesand calciruditic debris flows) derived from the shallow-water limestones of the Clarendon Block. KEY WORDS: WhiteLimestone Group, Jamaica, lithostratigraphy, palaeogeography. Figure 1. Simplified structural map of Jamaica, showing important normal faults that were active in Eocene to Miocene time, and distributionof the shallow-water carbonateplatforms developed on the structural blocks. -6- Introduction White Limestone Group have always been difficult to this subdivide. In paper, the history of the subdivision of The White Limestone Group represents the most the White Limestone is reviewed. Only formal geographically widespread lithostratigraphic unit at publications are considered, as theses are not considered outcrop in Jamaica, occupying some 60-65% of the formal publications under the guidelines of the island’s surface et 1982, and International Guide (Porter al., p. 113) giving Stratigraphic (Salvador, 1994) rise to extensive karst topography (Sweeting, 1958; (Appendix 1). This is followed by descriptions of three Versey, 1972; Fincham, 1998; Miller, 2004). Despite this, areas of White Limestone Group rocks and a suggestion it has received less detailed geological study than might be for the establishment of formal lithostratigraphic expected. This is largely due to its intense lithification, its formations. Only the shallow-water limestones of the of tendency to weather to rubble, and the presence most Clarendon Block, and deep-water limestones of the belts fossils moulds. and considered originally aragonitic now preserved only as troughs are here. The Blue Mountains and The formation is particularly important for other reasons. Hanover blocks have different sedimentary records It is extensively mined for the construction industry (Robinson, 1997; Mitchell, unpublished data), and need & all the economic schemes that (Henry Elliston, 1987; Geddes, 1987), separate lithostratigraphic are beyond the bauxite of Jamaica rest its karstified surface of deposits on scope this paper. Finally, the palaeogeography and (Hill, 1973; Comer, 1974) and it is the main freshwater depositional environments of the WhiteLimestone Group aquifer on the island (White, 1979). are considered. Deposition of the White Limestone Group occurred during a relatively tectonically quiescent phase in Historical review Jamaica’s geological history (Draper, 1987). During the Late Cretaceous to earliest Paleocene, the volcanic island De la Beche (1827, p. 169) referred to all the Tertiary arc chain, of which Jamaicawas a part, collided with the limestones in Jamaica as the ‘white limestone formation’ Yucatan Peninsula (Mitchell, in press). This produced an (Appendix 1), while Sawkins (1869) divided De la Beche’s extensive mountainous region, now the Upper Nicaragua unit into separate Yellow Limestone, White Rise. As left-lateral, strike-slip displacement began along Limestone, White Marl and Coast Limestone. the Caribbean-NorthAmerican Plate boundary (Pindell, Hill (1899, p. 65) divided the White Limestone in 1994), this land area underwent erosion and new fault Jamaica into two series; the Oceanic Series, or ‘Upland the fault White and systems propagated through area. Two major Limestone,’ the Coastal Series. In his table east-west set and northwest- he showed the Oceanic Series systems developed: an a (Hill, 1899, p. 42), as southeast set (Mann et al., 1985; Draper, 1987). These containing three units, the Montpelier, the Moneague and faults defined a set of blocks and troughs, the blocks (Blue the Cobre. The series is underlain by the Chapelton and and beds Yellow and overlain the Mountains, Clarendon Hanover; see Figure 1) Catadupa (= Limestone) by remained as isolated positive features, while the troughs Bowden Formation. Thus, Hill’s Oceanic Series is (Negril-Sav-La-Mar, Montpelier-Newmarket, North equivalent to Sawkins’s (1969) White Limestone and and John Crow underwent White and also to the modem of the White Coast, Wagwater Mountains) Marl, usage rapid subsidence. The rapid subsidence of the troughs led Limestone Group. However, on page 143, Hill (1899) to the deposition of hemipelagic sediments (deep-water included the Chapelton and Catadupa beds in the Oceanic facies of the Yellow Limestone Group) in the Middle Series! The Oceanic Series in Hill’s (1899, p. 42) table Eocene, and pelagic sediments (the deep-water chalks of was divided into what he thought were lower and upper the White Limestone Group) in the late Middle Eocene to parts. His lower part was called the Montpelier beds; Early Miocene. As the land areas were eroded and however, the names applied to the upper part were less Hill text; subsided, the platforms were transgressed by the sea; clearly given. used three names throughout the initially forming shallow-marinesiliciclastics and impure Moneague, Cobreand Brownstown, although only the first limestones of the YellowLimestone Group and finally, as two were described. However, the footnote on page 71, the land carbonates of and the of Brownstown 142, that areas were fully submerged, pure use on page suggest the White Limestone Group. In the Miocene, renewed Hill’s intention was to divide the Oceanic Series into tectonic deformationof Jamaica began (Wadge & Draper, lower (Montpelier) and upper (Brownstown) parts, with 1978; Krijnen & Lee Chin, 1978; Draper, 1987), and the the upper part split into lower (Moneague) and upper carbonate platforms were uplifted and exposed to (Cobre) portions. The Montpelier consisted of ‘... white karstification and erosion. the Pliocene- limestone nodules of flint...’ 1899, During ... containing (Hill, p. Pleistocene, new river systems cut down into the 70, quoting from Sawkins, 1869, p. 250). The Moneague siliciclastic sedimentary rocks of the Yellow Limestone Formation was described as ‘more massive limestones, Group and Cretaceous, and supplied detritus for the white in colour, firmer in texture, often semi-crystalline, deposition of the mixed clastic-carbonate rocks of the sometimes containing casts of fossil mollusks and solitary Coastal Group (Robinson, 1994). corals’, and the Cobre Formation as having an ‘irregular Because of their very pure lithologies, the strata ofthe lumpy texture’ (Hill, 1899, p. 76). -7- Member Description “ Troy Limestones Pink, white, yellow or brown limestones, well bedded, recrystallized tough and 35. and into dolomite recrystallized pp. 34, compact ...frequently magnesian grade pure ... series into miliolids and passes upwards, by intercalation, limestones with rare Dictyoconus” Swanswick Limestones “calcarenite, or limestone-sandstone, made up largely oforganic debris with a 34, 35. offoraminifera that other series the limestones by pp. greater variety any ... pass intercalation upwards into standard limestones with occasional beds made up of organic debris” " with the Fabularia and cookei Somerset Limestones junction Troy is clearly definable, as Dictyoconus p. 35 appear suddenly and are frequentin these limestones" GibraltarLimestones “equivalent to the Somerset Limestones in the south. It is temporary given a p. 36 separate name because it overlies the Swanswick member- not the Troy" Brown’s Town “complete incoherence and lack of structure of the limestones and also by the Limestones L. L. presence of a typical Antiguan fauna of Lepidocyclina undosa, fabulosa, 36 L. p. gigas and parvula” Montpelier “hard chalks, withflints, that are devoid ofthe largerforaminifera" p. 36 Walderston Limestones “limestone which is rich in small foraminifera, particularly miliolids and 37 buliminids and and p. often Archaias, Peneroplis

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