Mitchell, Simon F.
Author Affiliation, Ana.
Department of Geography and Geology
Stratigraphy of the Guinea Corn Formation (Upper Cretaceous) at its type locality between Guinea Corn and Grantham, northern Clarendon, Jamaica
Journal of the Geological Society of Jamaica
Date of Publication
1-12 (+4 Enclosures)
Eighth stratigraphic sections through the Guinea Corn Formation, exposed in the Rio Minho between Grantham and Guinea Corn (north-west Clarendon), have been logged in detail. The sequence is informally divided into seven units herein designated A to G from the base upwards. Unit A comprises interbedded siltstones and thin silty limestones, and provisionally it is divided into six sedimentary rhythms. Unit B comprises of more massive limestones with only minor amounts of siltstone or shale, and is divided into three rhythms. Unit C is represented by a return to interbedded limestones and siltstones and is divided into three rhythms. Unit D is a succession of massive limestones, which is divisible into six rhythms. Unit E represents an interbedded succession of siltstones and tuffaceous sandstones. Unit F is represented by five rhythms each of which shows an alternation of limestone and siltstone. Unit G consists of eighteen limestone beds, which yield abundant examples of the larger foraminiferan Chubbina. Lateral thickness variations in the relatively small area studied are rather dramatic, particularly for the tuffaceous units, which show rapid thinning laterally. Eight markers are described; these are: the Distefanella event (base of unit C); the Biradiolites robinsoni bed (unit C); the first Sauvagesia bed (unit C); the second Sauvagesia bed (unit D); the Cabbage Hill oncolite bed (unit D); the Praebarrettia bed (top of unit D); the Macgillavryia bed (base of unit F); and the Cabbage Hill lignite bed (base of unit G).....