CIPERO formation . Oligo-Miocene
Authors of name: CUSHMAN (J. A.) & STAINFORTH (R. M.)
(1945). The foramininifera of the Cipero marl formation of Trinidad, British West Indies. Cushman Lab. Foram. Res. Spec. Publ. no 14, p. 1-75, p. 1—16.
Type locality: Cliffs of coast between San Fernando and the mouth of Cipero River.
Thickness: 2 500-3 000 feet.
The thick series of faulted light coloured marls are subdivided by CUSHMAN & STAINIORTH into: I. Lower (Globigerina concinua) zone, II. Middle (Globigeriatella insueta) zone and
iii Upper III Globorotalia fohsi) zone. The dark, silty marl, lo¬cally called Bamboo Silt (LEHNER, 1935, p. 697) with the relatively rich orbitoidal fauna considered by VAUGHAN & COLE (1941, p. 28) to be of an upper rather than lower Oligocene age is nut included In the STAINFORTH’s Cipero formation as originally done by RENZ (1942, p. 547) in his definition of the Cipero formation. CUSHMAN & STAINFORTH place their Bam¬boo Clay in the topmost part of the San Fernando formation,
Whereby its position is explained as an upfaulted block of the youngest part of the San Fernando formation. The study of the meager molluscan fauna of the Bamboo Silt induces RUTSCH (in CUSHMAN & STAINFORTH, 1945, p. 11) to consider it to be of Rupelian or Chattian age. The Pleurophopsis and Thyasira fauna of the Globorotalia Fohsi zone of Freeman’ s Bay was tentatively correlated by Rutsch with the Heath formation and Lomitos cherts of Peru and given a provisional age of Upper Oligocene (CUSHMAN & STAINFORTH, 1945, p. 12). On this and other evidence an Oligocene age was attributed to the Cipero formation.
STAINFORTH (1948) subdivides the Cipero formation into the following lithological units with their corresponding biostrati¬graphic units:
Cacairo marl member of Globigerina fohsi zone
Cipero formation Globigerinatella insueta zone
? Flat Rock tongue of
San Fernando formation
Globigerina concinna zone
Paradise marl member of
Whereby the Flat Rock tongue represents LENHER’S Bamboo Silt KUGLER (1953, p. 46) believes the Flat Rock tongue to represent a slip mass.
Stainforth’s term Cacatro marl member is synonymous with the mappable units known as Upper Ste. Croix and Princes Town marl of WARING (1926) or Retrench Hill marl of ILLING (1928, p. 20) which accordingly have priority although the latter was wrongly correlated with Dunmore Hill marl.
The Cipero formation rests unconformably on the San Fer¬nando formation and is often separated from the younger Lengua formation by a clay pebble bed indicating an unconformity.
CUSHMAN & RENZ (1947b) introduce the Globigerina dissimilis zone and place it between the Globigerina concinna and Globigertnatella insueta zones.
BOLLI (1951b, p. 141) subdivides the Globorotalia Fohsi zone into 4 subzones based on subspecies of Globorotalia fohsi.
BRONNIMANN (1950) failed to discover any indisputable Globigerina cf. concinna in the Bamboo Silt or Flat Rock Silt tongue but proved the presence of numerous Globigerina cf. apertura and few Globigerina dissimilis which suggests to him Basal Oligocene age. BOLLI (1954) describes Globigerina cf. concinna as the new species Globigerina ciperoensis.
The partial invalidity of the numerous formation names attributed to the Cipero formation are listed in STAINFORTH’S paper of 1948.
KUGLER (1953, p. 50), places the Globorotalia Fohsi zone into the Miocene and points to the possibility of the same age for the insueta zone. Subsequently (1954) he suggests the proba-bility of a still further lowering of the top Oligocene boundary.
At the meeting of Pointe-a-Pierre (1955), it was agreed that the Cipero formation should include two arenaceous facies members — the Herrera member and the Retrench member. Accordingly, the following addition to the definition should be made: The arenaceous facies of the Cipero formation is repre¬sented by the Retrench member of the Globigerina insueta zone and the Herrera member of the Globorotala fohsi zone
(H. G. KUGLER).
References: WARING (G. A.) (1926); ILLING (V. C.) (1928);
LEHNER (E.) (1935); VAUGHAN (T. W.) & COLE (W. S.) (1941);
RENZ (H. H.) (1942); CUSHMAN (J. A.) & RENZ (H. H.) (194Th);
STAINFORTH (R. M.) (1948); BRONNIMANN (P.) (1950); BOLLI (H. M.)
(1951b); KUGLER (H. G.) (1953); BOLLI (H. M.) (1954); KUGLER
(H. G.) (1954).
Diagram showing the biostratigraphic zonation using benthonic and planktonic Foraminifera
Retrench Marl, Retrench Village
Picton Anticline , Debe
Outcrop of the 14a Cipero along the western side of the north bound lane of the Sir Solomon Hochoy Highway in Debe. Made up of alternating bands of light and dark coloured claystones. Beds are also of varing thickness.