Estudios microflorísticos del Ordovícico de la Sierra de Zenta, Cordillera Oriental Argentina
ABSTRACT. This Doctoral Thesis presents the integrated research on the Ordovician microfloras recorded in the Sierra de Zenta of Jujuy and Salta provinces in NW Argentina. This study was carried out on the basis of systematic analysis of palynomorphs, mainly acritarchs, that were complemented with o...
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- Formato:
- Tesis Libro
- Lenguaje:
- español
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Tucumán
Universidad Nacional, Facultad de Ciencias Naturales e Instituto Miguel Lillo
2009
- Colección:
- Tesis: Doctora en Geología
Directora: Dra. María del Milagro Vergel
Co-Director: Dr. Guillermo F. Aceñolaza
Láminas: h.255-270
Tablas: 311-315
Bibliografía: h. 323-364
Nº de orden interno: TDG- 53 - Materias:
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| Sumario: | ABSTRACT. This Doctoral Thesis presents the integrated research on the Ordovician microfloras recorded in the Sierra de Zenta of Jujuy and Salta provinces in NW Argentina. This study was carried out on the basis of systematic analysis of palynomorphs, mainly acritarchs, that were complemented with other groups as chitinozoans and cryptospores. The Sierra de Zenta is located on a transitional zone between the Cordillera Oriental and the Sierras Subandinas, sharing common charaters to either one or the other geological unit depending on the analyzed area. The northern sector of the Sierra deisplays similar characters to the Cordillera Oriental, with the presence of the Santa Rosita and Acoite formations (Santa Victoria group). The central and southen sector of the Sierra de Zenta presents a great resemblance to the Sierras Subandinas, although not sufficient as to use the nomenclature of their Ordovician units. Considering the early statement, this paper defines informal units for the area. The age of the analyzed strata is based on biostratigraphical information, the presence of acritarch taxa and the defined palynological associations. Two geological profiles are described, a continous one in the northern sector of the Abra de Zenta - Abra Límite, and another that is represented by an integrated section revelated in the central part of the Sierra, Between the Abra Buey Ojo - Laguna Verde. The last stratigraphical sector is composed by four partial sections. The palynological sampling of the whole area allowed a detailed systematic desciption of acritarchs and a brief descrption of additional elements. Acritarchs are dominante elements, while prasinophyte, chitinozoans, cryptospores and spores represent minor escorting microfossils. Based on acritarchs records, five informal associations were defined whose ages were asigned according to the chronostratigraphical distribution of the taxa componets (ASZ). In the Abra de Zenta - Abra Límite, the palynological associations ASZ1, ASZ2 and ASZ3 have been defined. ASZ1 is assigned to a late Lower Tremadocian, ASZ2 to the Floian without being ruled out a possible Late Tramadociano age. ASZ3 records the Dapingian. The ASZ4 and ASZ5 associations are defined in the central and southen part of the Sierra de Zenta, included in the Abra Buey Ojo - Laguna Verde section. On the basis of itd paleontological elements, the ASZ4 is Floin to Dapingian and ASZ5 is Dapingian to Darriwwilian/Sanbdian. Thesee associations are compared to early described material from other Ordovician sequences of Argentina and diverse regions of the world, establishing some partial bioestratigraphical and paleogeographical correlations. The enviromental condition for the Ordovician strata of Zenta is inferred as well, on the basis of the sedimentary characters of the sequences and the palynological associations. |
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| Descripción Física: | 364 h. il.color,láminas,tablas,1CDRom (texto completo) 29,5 cm. |