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1 March 2012 Palaeodemecological Analysis of Infaunal Bivalves “Lebensspuren” from the Mulichinco Formation, Lower Cretaceous, Neuquén Basin, Argentina
Javier Echevarría, Susana E. Damborenea, Miguel O. Manceñido
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The study of palaeodemecological features requires some particular taphonomic conditions. These conditions were met in the Mulichinco Formation (Valanginian), where burrowing bivalve trace fossils are widespread and often appear in cross section on bedding surfaces. Two groups of such beds were analyzed, measuring population density, spatial distribution, size distribution and horizontal orientation of the burrows. The palaeoenvironment was established by means of a detailed sedimentological analysis, and the bivalve fauna present was checked, in order to attempt identifying their potential producers. High population densities were found in the two groups, indicating favourable physical conditions and good food supply, while differences in both spatial and size distributions were noticed between them; on most surfaces there was no preferred orientation. The first group (group A) showed a uniform pattern of spatial distribution and larger traces, with a remarkable absence of small sizes. In the second group (group B), the spatial distribution pattern is indistinguishable from a random distribution (except one case in which the pattern appears to be aggregated). Group A is interpreted as a set of escape traces made by deep burrowers in response to storm deposition, while group B is considered as resting/escape traces made by shallow burrowers in tide-dominated environments. Palaeodemecological studies of this kind are potentially useful tools for sedimentary and basin analyses.

Javier Echevarría, Susana E. Damborenea, and Miguel O. Manceñido "Palaeodemecological Analysis of Infaunal Bivalves “Lebensspuren” from the Mulichinco Formation, Lower Cretaceous, Neuquén Basin, Argentina," Ameghiniana 49(1), 47-59, (1 March 2012).
Received: 17 January 2011; Accepted: 1 June 2011; Published: 1 March 2012
Cretácico Temprano
Densidad poblacional
Disposición espacial
Early Cretaceous
population density
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