INVESTIGADORES
NOETINGER Maria Sol
congresos y reuniones científicas
Título:
FIRST RECORD OF A DEVONIAN PALYNOLOGICAL ASSEMBLAGE FROM THE ZENTA RANGE, EASTERN CORDILLERA, NORTHWESTERN ARGENTINA
Autor/es:
NOETINGER, S.; DI PASQUO, M. M.
Lugar:
Florianópolis, Brasil
Reunión:
Simposio; XII Simposio Brasileiro de Paleobotanica e Palinologia; 2008
Resumen:
@font-face {
font-family: "Cambria";
}p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0cm 0cm 0.0001pt; font-size: 12pt; font-family: "Times New Roman"; }div.Section1 { page: Section1; }
Devonian surface and subsurface deposits are recognized
between Bolivia, Paraguay and Argentina. In the latter,the Silurian- Devonian
units, represented by shale and sandstone facies deposited mainly in a shallow
marine environment are well developed in the Eastern Cordillera,
the Subandean Range and the subsurface of the Chaco-Salteño Plain. This study presents a preliminary
palynological survey from the Abra Límite locality (S
23º 10,858, W 65º 0,343) in the Zenta Range at the Eastern
Cordillera, Jujuy Province. The outcrop comprises heterolithic facies at the base, followed by thick packages
of sandstones interbedded with less thick beds of conglomerates and shales to fine-grained sandstones (ca. 250
m thick) and finishes with a greenish-grey diamictitic bed (ca. 50 m thick) in unconformable contact.
The section below the unconformity yielded poorly
preserved palynological material due to relatively high
level of thermal maturity. The basal part is characterized mainly by chitinozoans, such as Cingulochitina serrata,
Angochitina chlupaci, Hoegisphaera sp. cf. H. glabra, Ancyrochitna tomentosa, and several species left in open
nomenclature due to the rather poor preservation (e.g. Ramochitina sp.). These taxa are accompanied by few species
of phytoplankton (e.g., ?Multiplicisphaeridium
robertinum, Diexallophasis remota, Multisphaeridium
ramusculosum, Veryhachium sp.) suggesting an offshore palaeoenvironment for this association. Two samples of the
upper section yielded spores and phytoplankton. The stratigraphic distribution of species like Cingulochitina
serrata, Ancyrochitina tomentosa, Angochitina chlupaci and Hoegisphaera sp. cf. H. glabra suggests an Early
Devonian (?Late Lochkovian) age for the lowest part of
the studied section represented by the BAFC-Pl 2088 and
2089; whereas a late Eifelian to Givetian age is given to the upper section (BAFC-Pl 2086 and 2092) mainly based on
the appearance of Diboliporites farraginis. The levels in between (BAFC-Pl 2090 and 2091) are delimited by
the ages given above. Therefore, the proposed transgression for the Early Devonian, which marks the origin
of the basin expansion, is registered in this area. In
contrast, the upper part of the succession denotes a clear
environmental change in accordance with the lithology, the lack of marine phytoplankton and chitinozoans, and the
occurrence of some fresh or brackish water taxa, such as Quadrisporites variabilis, Quadrisporites
granulatus; ?coenobial algae, and sporomorphs.