CUCHE FORMATION

Age: early Cretaceous - Barremian through Aptian

The Cuche Formation consists of dark grey to black silty shales with occasional intercalations of arkosic quartz arenites, and in its upper part marly shales separated by some workers into the Maridale Member. Boli (1959) divided the Cuche Formation into two zones:

Lenticulina ouachensis zone - the older of the two where benthic taxa strongly dominate over planktic formanifera.

Lepoldina protuberans zone- the younger zone which contains a rich and diversified planktic fauna probably representing a deepening of the basin due to a continued normal fault activity. Outcrops of the Cuche Formation occur in the core of the central range mainly on the eastern section of the island.

Renz (1942) introduced the term 'Cuche Formation' and divided it into the La Carriere shale mamber below and the Marridale member above. The formation consists of a thick series of dark shales of 200 feet minimum and perhaps ammounting to as much as 5000 feet in thickness, with suborninate quartzose sands and conglomeratic limestones.

Three lithotypes are recognised:

*Black, silty, micaceous with lignitic or carbonaceous laminae which appear to be slightly metamorphosed or have undergone considerable diagenisis.

*Moderately well sorted, very fine grained to coarse grained sublith arenites to quartz arenites. Contain mudstone ripus clasts.

*Reddish-brown clay ironstone conglomerate with intercalatations of grits (cherry cake conglomerate)

Maridale Marl: Hutchison observed a belemite bearing, foraminiferal marl. Renz (1942) described Neohibolites aptiensis and Neohibolites semicanaliculatus.
Encountered in the following wells Laventille #1 (shale/limestone), Northern Basin #1, Guaico #1, Mt. Harris #1, Esmeralda #1, Montserrat #1, Iguana River 1 and Ste. Croix 1.

Quartzose sandstone

All Photographs by C. Archie

SUMMARY OF LOWER CRETACEOUS CUCHE FORMATION
(MT. HARRIS #1, ESMERALDA #1, AND FIELD SAMPLES

· ENVIRONMENT OF DEPOSITION Shelfal to Bathyal

Lithologies
· Moderately well sorted, very fine-gramed sublitharemtes to quartzarenites. Composed of monocrystalline quartz, feldspars and lithic fragments (cherts and metamorphic detritus).

· Clayey siltstones containing authigenic siderite and ferroan dolomite in the intergranular areas. The siltstones are arkosic in composition.

· Red claystone clasts from the "Cherry Cake" member of the Cuche Formation consists of varying proportions of quartz, hermatite and clay.


Cements
· fron oxide cement have formed within the clay matrix and on surfaces of detrital grains.

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