102 



TJNITED STATES NATIONAL MXJSEXJM BULLETIN 215 



of the small promontory, the type locality of the 

 Globigerinatella insueta zone. Type sample Bo 354 

 (TTOC 207274). 



Lithology: Light bluish grey marl with black 

 streaks. 



Remarks : Oloborotalia fohsi robusta BoUi, the zonal 

 marker, is restricted to the zone. It develops from 

 Globorotalia fohsi lobata Bermudez, which becomes 

 extinct in the basal part of the zone. Samples con- 

 taining Globigerinoides rubra (d'Orbigny) but without 

 Globorotalia fohsi robusta are occasionally encountered 

 at the top of the zone. Typical Globorotalia menardii 

 (d'Orbigny) appears late in the Globorotalia fohsi 

 robusta zone and continues into the Lengua formation. 

 Such typical species as Sphaeroidinella rutschi Cushman 

 and Renz, Hastigerina cf. aequilateralis (Brady), 

 Globigerina nepenthes Todd, and Globorotalia lenguaensis 

 Bolli, new species, commence in the lower Lengua; 

 they have not been observed in the Cipero formation. 

 The lithology grades from a highly calcareous marl in 

 the Cipero formation to a calcareous clay in the Lengua 

 formation. 



The Lengua Formation 



The Lengua formation of south Trinidad (Renz, 

 1942, p. 560) formerly known as "Green Clay" and 

 "Sphaeroidinella Clay," consists predominantly of a 

 greenish, calcareous clay, weathering buff to yellow grey 

 in color. The Lengua formation overlies the Cipero 

 formation, often with an apparently normal contact. 

 In certain areas the lower part of the Lengua formation 

 can be replaced by the more clayey-sUty Karamat 

 formation which also may replace part of the uppermost 

 Cipero. Upwards, the Lengua formation becomes 

 gradually replaced by the clays, silts, and sands of the 

 Cruse formation which are practically void of planktonic 

 Foraminifera. Marl-boulder and clay-breccia beds of 

 great thickness (Rio Claro boulder bed) are known from 

 the Lengua formation. 



The zonation of Trinidad sediments based on plank- 

 tonic Foraminifera which, almost without interruption, 

 can be applied from the Cretaceous onwards, comes to 

 an end at the top of the Lengua formation. With few 

 exceptions, the later conditions were no longer locally 

 suitable for planktonic Foraminifera. Preliminary in- 

 vestigations in more favorable sections of the Agua 

 Salada group in Falc6n, Venezuela, show, that such 

 characteristic species as Globigerina nepenthes Todd, 

 Sphaeroidinella grimsdalei Keijzer, Globoquadrina alti- 

 spira altispira (Cushman and Jarvis), Globoquadrina 

 dehiscens (Chapman, Parr, and Collins) became extinct 

 between upper Lengua time and the Recent. Numer- 

 ous other planktonic species, e. g., Globigerina bulloides 

 d'Orbigny, Globigerina eggeri Rhumbler, Globorotalia 

 truncatulinoides (d'Orbigny), and Globorotalia tumida 

 (Brady), originate during this time interval. 



As is the case with the Cipero formation, the thickness 

 of the zones of the Lengua formation is subject to con- 

 siderable variation. The whole formation may attain 



a thickness of over 2,000 feet but is usually less. For 

 instance in the Barrackpore-Penal area the average 

 thickness of the Globorotalia menardii zone is 600 feet 

 and of the Globorotalia mayeri zone 150 feet. 



The Lengua formation is here divided into the fol- 

 lowing zones (from bottom to top) : 



Globorotalia mayeri Zone 



Type locality: In a ditch on the east side of the 

 Cunjal Road, about 150 feet from its junction with the 

 Realize Road, about 2%. miles south southeast of 

 Lengua Settlement, south Trinidad. Coordinates 

 N:205000 links; E:419600 links. Type sample KR 

 23422 (TTOC 160021, 160634). 



Lithology: Buff to yellow grey, calcareous clay, 

 gypsiferous and limonitic. 



Remarks: The zonal marker Globorotalia mayeri 

 Cushman and EUisor ranges from the Globorotalia opima 

 opima zone through the Cipero formation into the lower 

 Lengua; the top of the Globorotalia mayeri zone is mark- 

 ed by the extinction of this long-ranging form. The 

 following species appear first in the Globorotalia mayeri 

 zone and continue into the Globorotalia menardii zone: 

 Globigerina nepenthes Todd, Globorotalia lenguaensis 

 Bolli, new species, Sphaeroidinella rutschi Cushman and 

 Renz, Globigerinoita morugaensis Bronnimann and 

 Hastigerina cf . aequilateralis (Brady) . 



Globorotalia menardii Zone 



Type locality: In a ditch on the east side of the 

 road leading from Lengua Settlement to Cipero - Ste. 

 Croix, about 150 feet from the road junction in Lengua 

 Settlement, about 1 mile south of Princes Town, south 

 Trinidad. Coordinates N:208900 links; E:413600 links. 

 Type sample KR 23425 (TTOC 178890). 



Lithology: Buff to yellow grey, calcareous clay, 

 gypsiferous and limonitic. 



Remarks: The only distinction between the Globo- 

 rotalia menardii zone and the underlying Globorotalia 

 Tnayeri zone is the absence of Globorotalia mayeri Cush- 

 man and EUisor in the Globorotalia menardii zone. 



Age of Cipero and Lengua Formations 



Until recently the Cipero formation was generally 

 regarded as entirely Oligocene in age (Cushman and 

 Stainforth, 1945; Stainforth, 1948b, etc.). Globoro- 

 talia fohsi, originally described from the Miocene, was 

 considered to be a typical representative of the upper 

 Oligocene in the Caribbean region. 



A recent paper on the Miocene-OMgocene boimdary 

 by Eames (1953) initiated a controversy on the place- 

 ment of that boundary in the Caribbean region. 

 Comments on the problem were subsequently made by 

 Stainforth (1954), Eames (1954, 1955), Kugler (1954), 

 and Drooger (1954, 1956). Evidence brought forward 

 by some of these contributors indicates that the Oligo- 

 cene-Miocene boundary in the Caribbean region had 

 been placed too high when compared with that of 

 Europe and other areas. Considering the reasons 



