Tafonomia dos Pygocephalomorpha (Crustacea, Peracarida), subgrupo Irati, Permiano, Bacia do Paraná, Brasil: implicações paleoecológicas e paleambientais
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Data
2011-10-03
Autores
Silva, Suzana Aparecida Matos da [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Crustáceos (Pygocephalomorpha, Peracarida) são elementos comuns e conspícuos do registro paleontológico da Formação Assistência, Subgrupo Irati, Permiano, na Bacia do Paraná. Para o presente estudo foram analisadas amostras provenientes da base do Membro Ipeuna, nos municípios de Saltinho, Rio Claro, Tiête, Limeira, Cesário Lange, Angatuba e Pereiras, complementadas por material proveniente da Formação Irati, do afloramento de Passo do São Borja, município de São Gabriel, RS, correlacionável ao intervalo Assistência do Estado de São Paulo. O espectro de preservação dos pigocefalomorfos inclui três modos de ocorrência: Tipo 1- Pigocefalomorfo completo com corpo esticado (=complete outstreched bodies) ou flexionado, o qual esta associado a lamitos de cor creme e mais comumente aos folhelhos negros e, em raros casos, com moldes de partes moles preservadas; Tipo 2- Pigocefalomorfo parcialmente articulado (carapaça e abdômen com/sem leque caudal), esticado ou flexionado, o qual esta presente em pelitos creme, associados a estratificações cruzados do tipo hummocky intercalados em sucessão de folhelhos pretos, pirobetuminosos e Tipo 3- Pigocefalomorfo desarticulado, com escleritos isolados (apenas carapaças, abdômen ou segmentos do abdômen). Este modo de preservação inclui restos isolados, desarticulados e fragmentados, especialmente da carapaça e do abdômen. Trata-se do modo predominante de preservação nas amostras aqui estudadas. Este modo de ocorrência é marcado pela presença de restos isolados ou ainda por acumulações densas de restos de crustáceos. Quatro tipos principais de acúmulos densos foram observados, informalmente indicados por letras: Concentração do tipo 3A, incluindo micro-coquinas formadas por acúmulos decimétricos a centimétricos de diminutos fragmentos angulosos...
Crustaceans (Pygocephalomorpha, Peracarida) are common elements in the paleontological record of the Assistência Formation, Irati Subgroup of the Permian, in the State of São Paulo and in coeval rocks of the Paraná Basin. For the present study, samples taken from the base of the Ipeuna Member from the municipalities of Saltinho, Rio Claro, Tiête, Limeira, Cesário Lange, Angatuba and Pereiras were analyzed, complemented by material obtained from the outcrop at Passo do São Borja (Irati Formation) in the Municipality of São Gabriel, Rio Grande do Sul, which is correlated with the Assistência interval in the State of São Paulo. The preservation spectrum of the pygocephalomorphs includes three modes of occurrence: Type 1- Complete (extended bodies or flexed) pygocephalomorphs, which are associated with mudstones and more commonly with black shales and, in rare cases, with the soft parts preserved; Type 2- Partly articulated (carapace and abdomen with or without caudal fan) pygocephalomorphs, extended or flexed, which are present in cream-colored pelites, associated with hummocky cross-stratifications, successively intercalated with pyrobetuminose, black shales; and Type 3- Disarticulated pygocephalomorphs, with isolated sclerites (only carapaces, abdomen, or abdominal segments). This mode of preservation includes isolated remains, disarticulated and fragmented, especially of the carapace and abdomen. It is the predominant preservation mode in the samples studied here. This mode of occurrence is marked by the presence of isolated remains, or also by dense accumulations of crustacean remains. Four main types of dense accumulations were observed, indicated informally by letters: Concentration type 3A, including micro-coquinas formed by decimeter- to centimeter-thick accumulations of tiny... (Complete abstract click electronic access below)
Crustaceans (Pygocephalomorpha, Peracarida) are common elements in the paleontological record of the Assistência Formation, Irati Subgroup of the Permian, in the State of São Paulo and in coeval rocks of the Paraná Basin. For the present study, samples taken from the base of the Ipeuna Member from the municipalities of Saltinho, Rio Claro, Tiête, Limeira, Cesário Lange, Angatuba and Pereiras were analyzed, complemented by material obtained from the outcrop at Passo do São Borja (Irati Formation) in the Municipality of São Gabriel, Rio Grande do Sul, which is correlated with the Assistência interval in the State of São Paulo. The preservation spectrum of the pygocephalomorphs includes three modes of occurrence: Type 1- Complete (extended bodies or flexed) pygocephalomorphs, which are associated with mudstones and more commonly with black shales and, in rare cases, with the soft parts preserved; Type 2- Partly articulated (carapace and abdomen with or without caudal fan) pygocephalomorphs, extended or flexed, which are present in cream-colored pelites, associated with hummocky cross-stratifications, successively intercalated with pyrobetuminose, black shales; and Type 3- Disarticulated pygocephalomorphs, with isolated sclerites (only carapaces, abdomen, or abdominal segments). This mode of preservation includes isolated remains, disarticulated and fragmented, especially of the carapace and abdomen. It is the predominant preservation mode in the samples studied here. This mode of occurrence is marked by the presence of isolated remains, or also by dense accumulations of crustacean remains. Four main types of dense accumulations were observed, indicated informally by letters: Concentration type 3A, including micro-coquinas formed by decimeter- to centimeter-thick accumulations of tiny... (Complete abstract click electronic access below)
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Palavras-chave
Crustaceo, Paleontologia – Brasil, Tafonomia, Parana, Rio, Bacia
Como citar
SILVA, Suzana Aparecida Matos da. Tafonomia dos Pygocephalomorpha (Crustacea, Peracarida), subgrupo Irati, Permiano, Bacia do Paraná, Brasil: implicações paleoecológicas e paleambientais. 2011. 74 f. Dissertação - (mestrado) - Universidade Estadual Paulista, Instituto de Geociências e Ciências Exatas, 2011.