100 



■UNITED STATES NATIONAL MUSEUM BtJLLETIN 215 



from the similar facies of the Moimt Moriah silt member 

 of the upper Eocene San Fernando formation. Those 

 beds which have a Movmt Moriah silt aspect but do 

 not contain any Eocene foraminiferal markers are 

 here placed in the Oligocene part of the Cipero forma- 

 tion. The Globigerina ampliapertura zone commonly 

 also occurs in a calcareous clay that weathers to a light 

 creamy-brown color and as such is different from the 

 Moimt Moriah silt. 



The thickness of a single Cipero zone may vary 

 considerably, even within such a small area as the 

 Barrackpore oilfield (BQggins, 1955). In a normal 

 sequence of beds one expects a zone to measure several 

 himdred feet, but thicknesses of over 1,000 feet have 

 been recorded, especially for the Globorofalia fohsi 

 rohusia, zone. The Globorotalia fohsi lobata zone, on 

 the other hand, is usually rather reduced in thickness, 

 seldom exceeding 200 feet. Often one or several zones 

 are foxmd to be completely absent, either due to non- 

 deposition or to subsequent submarine erosion. 

 Because of these irregularities it is diJB&cult to give even 

 an average thickness for any zone. 



There is a very strong predominance of planktonic 

 Foraminifera in the Cipero formation which according 

 to Stainforth (1948b, p. 1321) fulfills the requirement 

 for a fossil Globigerina ooze. Stainforth (1948b, p. 

 1320) counted several thousand Foraminifera in random 

 samples of Cipero marl, which gave the following 

 results: 



Zone I (= Globigerina ciperoensis ciperoensis zone): 

 several hundred planktonic to each benthonic 

 specimen. 



Zone II {=Gl6bigerinatella insueta zone): 2197 plank- 

 tonic to 37 benthonic specimens (59:1). 



Zone III (_= Globorotalia fohsi lobata zone): 2984 plank- 

 tonic to 119 benthonic specimens (25:1). 



The Cipero formation is here divided into the 

 following zones (from top to bottom): 



Clobigerina ampliapertura Zone 



Type locality: In left side branch of a guUy, 800 

 feet northeast of north end of San Fernando railway 

 station, 250 feet southeast of railway bridge. Coordi- 

 nates N:237850 links; E:357560 links (Coordinates are 

 given according to the Government cadastral sheets of 

 12 chains to 1 inch, almost 1:10,000). Type sample 

 SE 4668 (TTOC 246756). 



Lithology: Massive, sUty, impure, sepia colored 

 marl. 



Remarks : The Globigerina ampliapertura zone, for- 

 merly kaown as the Globigerina apertura zone (Suter, 

 1951) is characterized by the zonal marker and by 

 Globigerina parva BoUi, new species. Both species 

 occur also in the upper Eocene but such character- 

 istic forms as Hantkenina, Globorotalia centraHs Cush- 

 man and Burmudez, Globorotalia cocoaensis Cushman, 

 Bulimina jacksonensis Cushman, became extinct at the 

 close of the Eocene. Several planktonic species ap- 

 parently originate in the Globigerina ampliapertura 



zone, e. g., Cassigerinella chipolensis (Cushman and 

 Ponton), and Globigerina ciperoensis ciperoensis Bolh. 

 In the interval after the extinction of Globigerina 

 ampliapertura and before the first occurrence of Glo- 

 borotalia opima opima BoUi, new species, new subspecies 

 (marker for the next younger zone), a comparatively 

 monotonous planktonic faima occurs, consisting pre- 

 dominantly of Globigerina cf. venezuelana Hedberg. A 

 separate zone could be erected for this interval, but in 

 order to avoid unnecessary complication this interval 

 has here been included in the Globigerina ampliapertura 

 zone and is referred to as its upper part. This upper 

 part of the Globigerina ampliapertura zone is well 

 exposed northeast of the type locality (in a gully 1,100 

 feet northeast of the north end of the San Fernando 

 railway station, 200 feet southeast of the railway bridge, 

 at the bottom of a small water fall (Coordinates 

 N:238270 links; E:357940 links). 



Globorotalia opima opima Zone 



Type locality: Cipero type section, between 20 and 

 240 feet southwest from fixed point (see p. 103). Type 

 sample JS 20 (TTOC 193265). Rz 90 (TTOC 21721), 

 the type sample for Cushman and Stainforth's zone 

 I {Globigerina concinna zone), comes from the same sec- 

 tion. 



Lithology: Bluish grey marl with dark grey blotches, 

 gypsiferous; brown and yellow limonitic patches. 



Remarks : The zonal marker Globorotalia opima opima 

 BoUi, new species, new subspecies, is restricted to the 

 zone. Globigerina ciperoensis ciperoensis BoUi and 

 Globigerina venezuelana Hedberg are usuaUy abimdant. 

 Globigerina ampliapertura BoUi, new species and 

 Globigerina parva BoUi, new species, present in the 

 underlying zone, became extinct before the appearance 

 of Globorotalia opima opima. 



Globigerina ciperoensis ciperoensis Zone 



Type locality: Cipero type section, between 60 feet 

 northeast and 20 feet southwest of fixed point (see 

 p. 103). Type sample Bo 291A (TTOC 215656). 



Lithology: Green-brown marl with reddish iron 

 streaks. 



Remarks: The Globigerina ciperoensis ciperoensis 

 zone differs faunaUy from the Globorotalia opima opima 

 zone only in the absence of Globorotalia opima opima 

 BoUi, new species, new subspecies. The zonal marker 

 disappears at the upper limit of this zone. 



Globorotalia kugleri Zone 



Type locality: South bank of San Fernando By- 

 pass Road, approximately 240 feet northeast from the 

 north end of road bridge across the Siparia raUway line. 

 Coordinates N:225700 links; E:361900 links. Type 

 sample Bo 274 (TTOC 201223). 



Lithology: Grey and yeUow brown, mottled, cal- 

 careous clay, gypsiferous and limonitic. 



Remarks: The zonal marker Globorotalia kugleri 



