TAPHONOMIC INTERPRETATIONS ABOUT THE DEVONIAN OUTCROPS OF PARNAIBA BASIN, WEST EDGE.

The Devonian of the Parnaíba Basin has been the target of studies by several researchers due to the potential of hydrocarbon reserves in some localities. The rocks are represented by the Itaim, Pimenteiras, and Cabeças formations. The taphonomic analysis presented here were realized in a session from the Pimenteiras Formation, Meso-Devonian age, which originated in a marine platform environment with large transgressive and regressive events. Several data were collected in the field, it was first defined that the analysis would be performed in a grid system, with a dimension of 2m wide by 2m high, and at each fossil collected measurements were taken as width, height, and length. The taphonomic data collected were: conservation level (if the bioclast was fragmented or complete), positioning (according to the lodging, oblique or perpendicular), in case that the bioclast was articulated or not, and other observations were reported. To optimize taphonomic analysis all fossils/bioclasts were subdivided into three groups, in the first sub-group the mono-skeletal (consisting of fossils that have only one skeletal component), the second group is the bi-skeletal (bioclasts with two skeletal elements), and the multi-skeletal (those bioclasts that have more than two skeletal carapaces). In all the analyzed material (360 bioclasts) mono-skeletal bioclasts correspond only 6.9% of the evaluated material, characterized by 25 gastropod specimens. Bi-skeletal are 68.1% (245 samples), and this amount consists of brachiopods such as _Australocoelia palmata_, _Tropidoleptus_ sp., _Iridistrophia_ sp., _Derbiyna_ sp., _Orbiculoidea_ sp., _Australospirifer_ sp., _Pustulatia_ sp., _Coelospira_ sp., and other bivalves like _Nuculites_ sp. Finally, the multi-skeletal is 25% (90 bioclasts) of the material, represented by a great variety of crinoids. Drawing a vertical abundance curve, it can be observed that all bioclasts have an abundance peak between 1.10 m and 1.20 m in profile. It is noteworthy that bi-skeletal bioclasts have a second abundance peak at 1.70 m. This fact may be justified since most bivalve shells (68.59%) are not fragmented and are inarticulate showing that they have deposited in an environment without strong energy probably related to a higher isostatic level related to a sudden transgressive process. The taphonomic analyzes are not yet completed on the western side, although paleontological research is more common on the eastern side of the Parnaiba Basin, but studies are still been conducted here in unprecedented ways.