formacion batá - etayo_de porta
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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:[email protected] (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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