PALYNOLOGY OF THE PIAUI FORMATION, PENNSYLVANIAN OF THE PARNAIBA BASIN: BIOCHRONOSTRATIGRAPHY OF A SELECTED INTERVAL WITHIN THE BOREHOLE 1-UN-09-PI (CAXIAS, MA, BRAZIL)

PALYNOLOGY OF THE PIAUI FORMATION, PENNSYLVANIAN OF THE PARNAIBA BASIN: BIOCHRONOSTRATIGRAPHY OF A SELECTED INTERVAL WITHIN THE BOREHOLE 1-UN-09-PI (CAXIAS, MA, BRAZIL). The Pennsylvanian Piaui Formation, basal unit of the Balsas Group, is constituted by sandstones, shales and limestones, with scarce palynological records. This unit is interpreted mainly as continental to shorefacies in origin. This paper presents the palynostratigraphical results obtained for the interval between 110.60 m and 178.12 m of the borehole 1-UN-09-PI, located in Caxias, Maranhao State, which corresponds to the upper microclastic portion of this unit in the borehole. Most part of the twelve core samples studied urn shed palynological associations. Among the continental palynomorphs, saccate pollen grains are dominant, mainly taeniate bisaccate and non tateniate monosaccate species. Taking into account that there is no available palynological zonation of the Pennsylvanian-Permian interval of this basin, the scheme erected for the neighboring Amazonas Basin was used for comparisons. The records of certain species from spores and pollen, such as Raistrickia cephalata Playford & Dino, Protohaploxypinus amplus (Balme & Hennelly) Hart, Lunatisporites onerosus Playford & Dino, Verticipollenites sp., Striatopodocarpites sp. and Meristocorpus explicatus Playford & Dino, allow the correlation of most of the studied interval with the Raistrickia cephalata Zone, which was recognized for the middle portion of the Nova Olinda Formation (Amazonas Basin), regarded as Pennsylvanian (Moscovian) in age.