patarroyo et al. 2011 - gaea heidelbergensis

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22ndLAK 2011, Heidelberg Abstracts 165

AMMONITE AND INOCERAMID EVIDENCE FOR AN EARLY TURONIAN

(CRETACEOUS) AGE OF THE BASE OF THE LOMA GORDA FORMATION IN THE

UPPER MAGDALENA VALLEY BASIN, SOUTH-WESTERN COLOMBIA

PEDRO PATARROYO1

ANDRADE2

& PETER BENGTSON3

1: Departamento de Geociencias, Universidad Nacional de Colombia, Cr. 30 N. 4503, Bogot, Colombia:

[email protected] c/o Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120

Heidelberg, Germany

2: Universidade Federal de Sergipe, Ncleo de Geologia - NUGEO. Av. Marechal Rondon, s/n - Jardim Rosa Elze,

49100-000 So Cristvo, SE, Brazil: edilma@ phoenix.org.br

3: Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234, 69120 Heidelberg, Germany: peter.

[email protected]

The section studied is located along Bambuc Creek, north-west of the town of Aipe,

Department of Huila, south-western Colombia. The rocks form part of the AptianMaastrichtian

Magdalena Valley Basin. In this area the syncline is affected by local faulting and intersected to-

ward the south by the Chusma Fault System.

The TuronianConiacian Loma Gorda Formation is well exposed in the basin. The forma-

Group. Along Bambuc Creek, the Loma Gorda Formation reaches a thickness of 245 m and is

informally divided into three members. The boundary between the Hondita shales and the Loma

-

cro- and macrofossils.

The lower member of the Loma Gorda Formation consists of a 99-m-thick succession

of alternating micrites, biomicrites and black calcareous mudstones of varying thicknesses. The

mudstones contain fossiliferous carbonate concretions. Near the base of the lower member there

occur scattered phosphatic fragments, shark teeth and wood fragments. Approximately 6 m abovethe base, the ammonites Fagesiacf. thevestensis(Peron, 1896) and Neoptychitescf. andinus

(Leanza, 1967), the inoceramid bivalves Mytiloides kossmati(Heinz, 1933) and M. goppelnensis

(Badillet & Sornay, 1980) and the bivalveAnomiasp. were collected. The ammonites and inocer-

amids indicate an early Turonian age for the base of the Loma Gorda Formation.

The recommended stratigraphic nomenclature for the AptianMaastrichtian succession

internal reports of petroleum companies and in some publications and geological maps an al-

ternative nomenclature usage can be found (Villeta Group or Formation, Bambuc shale, La

Luna Formation, Monserrate Formation, etc.), which may lead to stratigraphical problems and

confusions. The Loma Gorda Formation studied here is approximately equivalent to the La Luna

Formation of Venezuela.

LAK2011.indb 165 16.03.2011 15:27:29 Uhr


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Stefan Gtz, Peter Bengtson,Francisco J. Cueto Berciano,

Wolfgang Stinnesbeck (Eds.)LAK 2011

22ndInternationalColoquium on

Latin American Earth Sciences

Abstracts and Programme

Heidelberg, Germany30 March - 1 April 2011

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A

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heidelbergensi

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http://www.lak2011.uni-hd.deISSN 0946-0535

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h e i d e l b e r g e n s i s

G A E A

covergaramond16.3G.indd 1 16.03.2011 16:37:15 Uhr


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