INVESTIGADORES
PONCE Juan Jose
congresos y reuniones científicas
Título:
Preservation of recent footprints in an estuarine tidal-flat with development of microbial mats: implications for the analysis of fossil tracks
Autor/es:
CARMONA, N.B.; CUADRADO D. G.; PONCE, J.J.; PIZANI N.
Lugar:
Denver Colorado
Reunión:
Conferencia; SEPM Research Conference Microbial Mats in Siliciclastic Sediments from the Archean to Present; 2010
Institución organizadora:
SEPM
Resumen:
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Field studies in a mesotidal flat in Bahia Blanca
estuary, Argentina, reveal the presence of extensive areas with microbial mats,
covering the upper-intertidal and lower-supratidal areas. Studies of recent environments
with microbial mats increased considerably during the last years, not only
because their unique sedimentologic and ecologic characteristics, but also
because they provide important implications for the understanding of fossil
environments and paleocommunities. The main purpose of this research was to
evaluate the role of microbial mats in the preservation of biogenic structures.
We recorded the distribution of recent traces all over the tidal-flat, although
focused the analysis on the preservation of large bird tracks. Several
footprints were selected and photographed, recording the morphological modifications
they experienced during four months. During this time, most of the footprints
showed resistance to tide- and wind-erosion, and also to heavy rains and storms
that affected the tidal-flat. This resistance was clearly associated to the
presence of the microbial mats, which are known to biostabilize the sediment. Also,
microscopic analysis of the tidal-flat sediment revealed the presence of
zeolites and calcite, suggesting early cementation, which may have favored the
consolidation of the footprints. Mat-thickness also affected the morphology of
the footprints; in areas with thick microbial mats overlying soupy sands, the
tracks were deeply impressed and did not show fine details. On the contrary, in
zones with thin microbial mats overlying relatively stiff muds, the traces were
shallow and preserved details such as skin impressions and skid-marks. Also, both
types of footprints were affected by mat growth, although in the shallow traces
the modification was faster, and the fine details were progressively
obliterated. This study yields valuable insights into the relationship between
microbial mats and morphology of the footprints, and provides key information for
the analysis of fossil tracks in equivalent paleoenvironments.