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The BataFormation of Colombia is truly Cretaceous, not Jurassic

F. Etayo Sernaa,*, N. SoleDe Portab, J. De Portab, T. Gaonaa

aDepartamento de Geociencias, Facultad de Ciencias, Universidad Nacional de Colombia, Santafe de Bogota, Cundinamarca, ColombiabDepartament dEstratigrafia i Paleontologia, Facultat de Geologia, Universitat de Barcelona, C/Marti Franquis s/n, 08028 Barcelona, Spain

Received 1 May 2001; accepted 1 July 2001

Abstract

The BataFormation has been a key unit in paleogeographic reconstructions of Colombia since it was first described as a Jurassic unit.

However, the paleontologic evidence for this age was not beyond doubt. The trigoniids collected from the upper part of the unit were

misidentified and should be referred to the late late Jurassic early Cretaceous genus Syrotrigonia. On palynomorph evidence, the

Interulobites triangularis, Cyclusphaera psilata, Classopolis, and Balmeiopsis limbatusassemblage indicates that the section should be late

Valanginian Hauterivian in age.

q 2003 Published by Elsevier Science Ltd.

Keywords:Bataformation; Microfossils; Bivalves; Early Cretaceous

Resumen

La Formacion Bataha sido clave en las reconstrucciones paleogeograficas de Colombia desde que fue descrita como una unidad delJurasico. Sin embargo la documentacion paleontologica para su datacion no estuvo libre de dudas. Los trigonidos colectados en la parte

superior de la unidad deben asignarse al generoSyrotrigoniade finales del Jurasico y comienzos del Cretacico. Con base en la asociacion de

los palinomorfos Interulobites triangularis, Cyclusphaera psilata, Classopolis y Balmeiopsis limbatus la edad de esta sucesion debe

considerarse Valanginiano tardoHauteriviano.

q 2003 Published by Elsevier Science Ltd.

Palabras clave:Formacion Bata; microfosiles; bivalvos; Cretacico temprano

1. Current status of the BataFormation

1.1. Name

The stratigraphic section measured at rock outcrops

along the road that follows the BataRiver near the town of

Santa Mara (Boyaca Department, Fig. l) was considered

representative of the (Rhetico)-Liasico by Burgl (1961,

Fig. 9). In his dissertation on the geology of Colombia,

Radelli (1967, pp. 105) cursorily called these beds

Formacion Santa Mara. It was Geyer (1967, pp. 16)

who first expressed the need to formalize this unit:

Zumindest der mittlere und obere Teil dieser Bata-

Formation (wie ich die Serie nennen mochte) is sicher

marin. This paragraph was overlooked by Ulloa and

Rodrguez (1979) when they wrote Se propone en este

trabajo el nombre de Formacion Bata, for the same section

described by Burgl. Thus, the formational name must be

credited to Geyer.

1.2. Boundaries

An erosional scar on well-indurated Carboniferous rocks

marks the base of the Bata Formation; it is probably

overthrust at the top by a thick, fine-grained shale unit

interpreted as Berriasian (Burgl, 1961).

1.3. Lithology

The light-colored conglomerate deposits exposed at the

base of the section named Conjunto A by Ulloa and

Rodrguez (1979) was derived from erosion of the

underlying sedimentary rocks. The upper part of the section

0895-9811/03/$ - see front matter q 2003 Published by Elsevier Science Ltd.

doi:10.1016/S0895-9811(03)00048-8

Journal of South American Earth Sciences 16 (2003) 113117www.elsevier.com/locate/jsames

* Corresponding author.

E-mail address:dgeologia@ciencias.ciencias.unal.edu.co (F.E. Serna).

http://www.elsevier.com/locate/jsameshttp://www.elsevier.com/locate/jsames

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Fig. 1. Location of the studied area, indicating the location of stratigraphic sections: I. the Bata Formation type locality, II. the Cumbre Formation t

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consists of medium-grained quartz sandstone and fine

conglomerate interbedded with black mudstone layers that

become dominant in the upper part of the section.

1.4. Thickness

Burgl (1961) indicated a thickness of 1300 m for this

section,Ulloa and Rodrguez (1979)presented it as having

1160 m, and our measurements, by the compass and tape

method, of the section above the conglomerate (Conjuntos

A and B) are shown inFig. 2.

1.5. Conventional age

The trigoniids collected byBurgl (1961)from the upper

part of the unit were identified as Trigonia aff. literataYoung and Bird, Trigonia (Geratrigonia) kurumensis

Kobayashi, and Trigonia lingonensis Dumortier and

referred to the Upper Liassic. Geyer (1973),who collected

fossils at the same locality, concluded that the Trigonia

belong to Vaugonia and described two new subspecies as

Vaugonia niranohamensis santa-mariae and Vaugonia

yokoyamai batafluviaethat were considered Lower Liassic.

D. Gutierrez (unpublished INGEOMINAS report, 1969)

also concluded that the fauna of the Bata formation belongto the Liassic (Ulloa and Rodrguez, 1979).

2. New age assignation for the BataFormation

Three lines of arguments support our assignment of the

Bata formation to the Cretaceous. First is taxonomic

reevaluation of Burgls (1961) and Geyers (1973) deter-

minations. We have measured the fossiliferous interval of

the type locality and collected additional material from the

same fossiliferous beds studied byBurgl (1961, his locality

HB2576) and Geyer (1973). Although we have had an

opportunity to cast Burgls original material, housed at the

Paleontological Collection of the Museo Geologico Jose

Royo y Gomez, INGEOMINAS, Bogota, we could not

locate Geyers specimens in the Paleontological Collection

of the Stuttgart University (Dr M. Senff, pers. comm.).Through the kindness of Drs T. Setoguchi and I. Hayami, we

were able to examine the plastoholotypes of the Japanese

species with which Geyer compared his specimens. As

previously suggested by Etayo Serna (inPerez and Reyes,

1986, 1997; Etayo Serna and de Porta, in prep.), the valid

assignment of Burgls and Geyers species is to Syrotrigo-

nia, the Peruvian congeneric species described by Lisson

(1930)as Trigonia forti,and Trigonia steinmanni from the

eocretacico of the outskirts of Huaylas (Upper Valangi-

nian, Alleman, 1987). Incidentally, in his paper, Lisson

(1930)remarked that his T. forti presented an affinity with

Trigonia literataYoung and Bird.

Geyers Cucullaea (s.l.) sp. ex gr. mabuchii Hayami,1958 is a common species and the subject of a systematic

study (Gaona, in prep.). By its heterodont dentition, it does

not belong toCucullaea. We refer our specimens to Cardiids

or Carditids inFig. 2.

Second, there is the comparative biostratigraphic argu-

ment. Following the revision of the Cretaceous stratigraphic

succession of the Middle Magdalena Valley (Etayo Serna,

1989) the lowermost Cretaceous units are, from bottom to

top: the fluviatile Los SantosArcabuco formations (Ber-

riasian?), followed by the intertidal to shallow marine

Cumbre formation and the platform carbonates of the

Rosablanca Formation of Valanginian age. The Cumbre

Formation hence represents the first marine ingression

during Early Cretaceous times into the Santander massif. In

this unit, we find the same Carditids as those found in the

Bata Formation and the Berriasian beds of the Ro Bata

section (Etayo Serna, 1989; herein,Fig. 2).Third, there is new paleontological evidence. We

measured and collected from the fossiliferous part of the

type section of the Bata Formation twice (1982 and 1997)

and have studied the palynomorphs of the two sets of

samples (29) with scant recovery except for samples 182056

and PEL8b. The latter belongs to the same bed, just above

the former.

Sample 182056 yielded the following taxa (see Fig. 2):

cf.Cyathidites

cf.Reticulatisporites

cf.Klukisporites

Klukisporitessp.Verrucosisporites sp.

Taurocusporitescf. segmentatusStover 1962

Interulobitescf. triangutaris (Brenner) Phillips 1971

Polycingulatisporites trabeculatus Archangelsky 1983

Pteridophytae indet.

Callialasporites dampieri (Balme) Dev 1961

Balmeiopsis limbatus(Balme) Archangelsky 1977

Classopollissp.

Foraminiferal linings

Dinoflagellate indet.

Sample PEL8b yielded the following taxa (seeFig. 2):

Aequitriraditescf. spinulosus (Cook. and Dett.)

Taurocusporitessp.

Trilobosporitessp.

Reticulatisporitessp.

Verrucosisporites sp.

Uvaesporitessp.

Klukisporitessp.

Cicatricosisporitessp.

Gleicheniiditessp.

Pteridophytaeindet.

Podocarpiditessp.

Callialasporitescf. dampieri (Balme) Dev 1961

Callialasporites trilobatus(Balme) Dev 1961Classopollissp.

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Fig. 2. Stratigraphic sections of the BataFormation and Cumbre Formations, according to different authors, showing distribution of taphonomic assemblages of bivalves and

shown inFig. 1.Ca, Cb, etc. are provisional paleontological nomenclature.

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cf.Cyclusphaera psilata Volkheimer and Sepulveda

(1976)

Cycadopitessp.

Foraminiferal linings

Dinoflagellate indet.

The assemblage of Taurocusporites segmentatus, Inter-

ulobites triangularis, Cyclusphaera psilata, Classopollis,

andBalmeiopsis limbatusappears in the basal Cretaceous of

Argentina (Archangelsky, 1980). For Archangelsky et al.

(1984), the chronostratigraphic assignation of this assem-

blange is Upper ValanginianHauterivian. The assemblage

is equivalent to that described by Volkheimer and

Sepulveda (1976), Archangelsky and Seiler (1980) from

the interval of the Agro Formation dated as late to early

Valanginianearly Barremian.Aguirre-Urreta et al. (1999)

confirm this age.

The palynological content of this part of the Bata

Formation corresponds with the Cyclusphaera Classopol-

lis assemblange of Volkheimer (1980) and the Interulo-

bitesForaminisporis zone ofArchangelsky et al. (1984),

which is characterized by C. psitata, B. limbatus, and T.

segmentatus and referred by these authors to the Upper

ValanginianHauterivian.

3. Conclusions

The Trigonia and Vaugonia species, on which theJurassic age of the Bata Formation was based, turned out

to be species ofSyrotrigonia,a genus known from the Upper

Jurassic (Upper Titonian) to Lower Cretaceous (Leanza,

1993). The palynomorphs recovered from this formation

correspond to those of the Upper ValangianianHauterivian

assemblages of Argentina. Dominance of Pteridophyta

indicates a humid regime, and the abundance of theSchizaeacea (?) Klukisporites suggest a warm climate.

This change in the assignation of age for the Bata Formation

enhances the paleogeographic interpretation of the Jurassic

of Colombia (cf.Geyer, 1979; Senff, 1995).

Acknowledgements

We thank Drs Takeshi Setoguchi (Kyoto University) and

Itaru Hayami (University of Tokyo) for kindly supplying the

plaster casts of some Japanese Vaugonia and Cucullaea.

Fieldwork was carried out with the assistance of G. Renzoni

and C. Ulloa (1982) and L. Daz (1997). We thank Geotec

Ltd for placing their facilities at our disposal and Mr Daniel

Carrillo for drawing the Figures. Reviews by Drs H. Duque

Caro, H. Parent, G. Gonzalez Bonorino, and an anonymous

reviewer of the English text significantly improved the

manuscript. This research has been supported by the

Universidad Nacional de Colombia, INGEOMINAS andthe Universitat de Barcelona.

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