Original paper

Preliminary study of the Paleocene Planktonic Foraminifera from the John Crow Mountains Belt, Postland, Eastern Jamaica

Fluegeman, Richard H.

Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 234 Heft 1-3 (2004), p. 121 - 136

25 references

published: Dec 22, 2004

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ArtNo. ESP155023400003, Price: 29.00 €

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Abstract

The John Crow Mountains Belt of easternmost Jamaica contains the only bathyal Paleocene marine rocks on the island. The lowermost Paleocene lithostratigraphic unit is the Moore Town Shales. The Moore Town consists of shale with interbedded turbidite sandstones. The upper Paleocene lithostratigraphic unit in the John Crow Mountains Belt is the Nonsuch Limestone. The Nonsuch Limestone is an evenly bedded micritic limestone interbedded with graded bioclastic layers. Both units contain planktonic foraminifera but poor exposures, tropical weathering, and faulting have hampered efforts to place the Moore Town Shales and the Nonsuch Limestone within a biostratigraphic framework. A section of the Moore Town Shales at the Fellowship Bridge over the Rio Grande River and a section of the Nonsuch Limestone at Turtle Crawle Harbour provide and opportunity to collect foraminifera from relatively unweathered rocks. The Moore Town Shales contain a foraminiferal fauna over 90% planktonics. The most abundant taxa in the lower part of the Moore Town are Globanomalina compressa, Subbotina triloculinoides, Parasubbotina pseudobulloides, Praemurica inconstans, and Chiloguembelina midwayensis. The upper part of the Fellowship Bridge section contains Praemurica uncinata and Subbotina triangularis. At Turtle Crawle Harbour, the Nonsuch Limestone contains a planktonic foraminiferal fauna with Morozovella angulata, Globanomalina chapmani, Igorina pusilla, Subbotina triangularis, and Subbotina velascoensis among others. Absent from this assemblage are Globanomalina pseudomenardii, Acarinina nitida, and Acarinina mckannai. The percentage of planktonic foraminifera among the total foraminiferal assemblages is lower than that of the Moore Town (less than 40%) and some samples have a considerably lower percentage. Planktonic foraminifera comprise less than 10% of the foraminifera collected from the uppermost sample of the Nonsuch Limestone at Turtle Crawle Harbour. The results suggest an assignment of the lower Moore Town Shales to biozone P1c with the upper part of the section at Fellowship Bridge assignable to biozone P2. The Nonsuch Limestone at Turtle Crawle harbour is likely assignable to biozone P3b. The Paleocene rocks in the John Crow Mountains record an early to middle Paleocene transition from a bathyal, clastic depositional setting to deposition on a carbonate platform.

Kurzfassung

Das einzige bathyale Paläozän Jamaica's findet sich in den Moore Town Shales im Ostzipfel der Insel, die vom Nonsuch Limestone überlagert werden. Neufunde von planktonischen Foraminiferen stellen die Moore Town Shales ins untere bis mittlere Paläozän (Zonen P1c und P2), den Nonsuch Limestone ins mittlere Paläozän (Zone P3b). Die untersuchte Abfolge enthält den Übergang von bathyalen klastischen Ablagerungen mit Turbiditen zu einer Karbonatplattform.

Keywords

John Crow Mountains BeltJamaicalithostratigraphicNonsuch LimestoneMoore Town Shalesforaminiferal faunaunweathered rocks