Middle Devonian chitinozoan biostratigraphy and sedimentology in the eastern outcrop belt of the Parnaíba Basin, northeastern Brazil

Abstract

This paper presents the first account of palynomorphs (chitinozoans) from the eastern outcrop belt of the Parnaiba Basin. The chitinozoans are obtained from shallow well core samples, penetrating the Pimenteira Formation, and indicate a late Eifelian-early Givetian age span for this stratigraphic unit, suggesting the absence of a 3 rd order unconformity. On the other hand, six minor forced regression unconformities (4 th /5 th order) occur in the Pimenteira Formation (sequences C-H by Young & Borghi, 2006). A major transgression, initiated in the late Eifelian, reached its maximum in the earliest Givetian, as evidenced by a Maximum Flooding Surface in Sequence D. The investigated sequences are also of interest for the hydrocarbon exploration of the basin, since the sediments include both source-rocks and reservoirs.

Palynostratigraphy of the Chapada Group and its significance in the Devonian stratigraphy of the Paraná Basin, south Brazil

“…Bergamaschi and . Similar conditions are known from the Parnaíba Basin (Grahn et al, 2008). The latest Emsian Tibaji Member of the Ponta Grossa Fm.…”

“…A minor gap is probably present at this level (cf. Grahn et al, 2008). The chitinozoan species Ancyrochitina varispinosa can be used as an index species for latest Emsian -late early Eifelian strata, from where the Alpenachitina eisenacki Zone marks the rest of Chapada unit 2 (Fig.…”

Reconstructing the terrestrial flora and marine plankton of the Middle Devonian of Spain: implications for biotic interchange and palaeogeography

“…In the Parnaíba Basin the chitinozoan Alpenachitina eisenacki is found in both sequences C and D, whereas Ancyrochitina flexuosa is restricted to sequence C and Fungochitina pilosa is found only in sequence D. These species occur in the Playa del Tranqueru section in this same sequential order, with F. pilosa first appearing about 27 m above A. flexuosa (Askew & Russell 2019). Grahn et al (2008) indicated the Eifelian-Givetian boundary as being at the boundary between sequences C Figures 4-6. Filled symbols represent locations with multiple assemblages very close to one another.…”

“…A further Brazilian scheme describes regressions at an even finer scale of fourth-fifth order, described as 'minor forced regression unconformities' (Young 2006;Young & Borghi 2006). This sequence stratigraphic analysis has been applied in late Eifelianearly Givetian rocks in the Parnaíba Basin that contain abundant palynomorphs, allowing potential marker species to be identified (Grahn et al 2008). Again, the rocks studied here can be likened on purely lithological grounds to the sandy sequence B followed by the much finer grained sequences C and D above.…”

Palynology and geochemistry of the Frasnian global transgression in the Parnaíba Basin, Brazil

“…Lange (1967) briefly mentioned chitinozoans from the Parnaíba Basin, and Cruz and Quadros (1985) described a new chitinozoan species from the latest Frasnianearly Famennian. More recently, chitinozoans have been discussed and correlated with miospores in papers by Grahn and Melo (2005), Grahn et al (2001Grahn et al ( , 2006Grahn et al ( , 2008 and Breuer and Grahn (2011). The Pimenteiras Formation consists of a lower Middle Devonian section, separated by a hiatus from the upper Late Devonian section.…”