| dc.description.abstract | This monograph is a requirement for the MSc’s degree. This work presents the
taxonomy, paleoecology and paleoenvironmental interpretation of the ostracods, as well
as a sedimentary facies approach from Estrada Nova and Irati formations (Passa Dois
Group) in the Paraná Basin. This approach allows us to subdivide these formations into
five facies associations named as 1 to 5, which might be observed in outcrops located in
the regions Alto Garças (MT) and Portelândia (GO). The facies analysis gives rise the
opportunity to the study the ostracod content of the Permian in the southerwestern Mato
Grosso State. Unfortunetely, the ostracod content has not been recovered in the Irati
Formation (facies association 1 and 2) which could be explained as a consequence of
the silica cementation. Only one individual was recovered in the Irati Formation.
However, the poor preservation became this individual unidentifiable. Herein, only
mesossaurs fossils could be illustrated. The ostracod content recovered in this work is
restricted to Estrada Nova Formation (facies association 4 and 5), in which fifteen
species of marine ostracods was illustrated: Basslerella sp. 1, Praepilatina sp. 1,
?Praepilatina sp. 2, Silenites sp. 1, Silenites sp. 2, Bythocypris sp. 1, Bairdiacypris sp.
1, ?Microcheilinella sp. 1, ?Miltonella sp. 1, Langdaia sp. 1, Gen. 1 sp. 1, Gen. 2 sp. 1,
Gen. 3 sp. 1, Gen. 4 sp. 1, Gen. 5 sp. 1. These species have been distributed in the
family Bairdiacyprididae, Pachidomellidae, Bairdidae, Miltonellidae, and Knoxitidae,
(besides Incertae family, with ostracods open nomenclature), which illustrate a
sprectrum of variations in salinity, habit, substrate and depth. Such variations suggest
these families have lived into a probably marine plataform which is near to the
coastline. The illustrated contents of ostracods and other microfossils as well as
macrofossils have not been in situ, which might be interpreted from the presence of: a)
articulated and disarticulated shells with surface fragmentation; b) fragmentation of
teeth and fish scales of paleonisciformes fishes; and c) disarticulated and semiarticulated bones the mesossaurs. Besides of the ostracod study, facies analysis
describes five facies associations which are related to a paleoenvironmental and/or
paleobathymetric reconstruction. The interpretation of the most important facies
features in these associations lead to interpret a mixed shallow marine shelf, dominated
by a wave carbonate setting gradually becaming more coastal with deltaic tendency.
This interpretation is suggested by the presence of marine ostracods, mesossaur
remains, passage of carbonate facies to siliciclastics toward the top of the succession, as
well as plants fragments. Together, these features do evidence a wide process of inland.
So, it might be possible to ascertain the association of facies 1to the shoreface
subenvironment into that previously interpreted shelf, which was suggested by the
predominance of limestone in addition to wave structures. The facies association 2,
siliciclastic and carbonate, characteristic of shale facies, is interpreted as a lagoon, due
to structures as bird-eyes and stromatolite in addition to shale nature. The facies
association 3 embraces interblended carbonate and calcareous pelite, partially silicified,
attributed to palustrine environment. The facies association 4 and 5 are siliciclastic and
presents beds of sandstones, siltstones and cm-scaled layers of calcirudite. These
deposits are respectively interpreted as prodelta (platform>) and distal sandy bars of the
prograding foreset in a deltaic setting. | |
