Full text
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| Author(s): |
Elver Luiz Mayer
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2011-06-30 |
| Examining board members: |
Walter Alves Neves;
Herculano Marcos Ferraz de Alvarenga;
Hussam El Dine Zaher
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| Advisor: | Walter Alves Neves |
| Abstract | |
The absence of information from the Brazilian Pleistocene mammalian fauna that goes beyond the taxonomic/descriptive studies and the lack of excavations with minimal stratigraphic control motivated the interventions in the Gruta Cuvieri (Lagoa Santa, Minas Gerais, Brazil) deposits applying a fine resolution excavation method. This method recorded in detail the spacial distribution of fossils as well as the sedimentologic context where the fossils were embedded, representing a pioneering foray to the national paleomastozoology. The objective of this work was to characterize part of the fossils exhumed from one of the excavated deposits, a pit named Locus 3, and to better understand the processes related with the development of this fossiliferous package. In order to do so, I analyzed the fossil material under two perspectives: 1) as skeletal elements, through the anatomic and taxonomic analysis and 2) as bioclasts, through the taphonomic analysis. In both approaches I also considered aspects of the spacial distribution of fossils. The results of the taxonomic analysis indicate the presence of 16 individuals of Tayassuidae, 9 of Cuniculus paca, 8 of Cervidae, 7 of Cuniculus major and 1 of Panthera onca. Considering these animals and those identified in other studies of Locus 3 the taxonomic variety represented in this pit is small, indicating a strong selection of groups incorporated therein. With regard to body weight there was the presence of animals of small, medium and large size, suggesting little selection for this feature. According to the spacial distribution of the remains of meso and megamammals, the latter were deposited only more recently, indicating that the Locus 3 potential for trapping animals had become more inclusive over time. The results of the taphonomic analysis indicate that the formation of the fossiliferous deposit was complex, involving processes that were acting often simultaneously and superimposed. Among the processes evaluated, the fragmentation was the most intense, acting from the necrolysis of the carcasses to after the final burial of the material. Trampling was identified as the main agent of material fragmentation, followed by the fall of animals and limestone blocks and by the compression of the sedimentary column. Weathering was the second most important factor in altering the original condition of the material. This feature modified the surfaces of the bone remains all over the fossiliferous package, suggesting slow sedimentation rate in Locus 3. Abrasion, another factor analysed, had a modest contribution in shaping the material, occurring iv mainly in the surface and due to the action of water, which in turn was important for the reworking of the material. Carnivores and rodents had also a small contribution to the fossiliferous package formation. The spacial distribution of the refitted pieces indicates predominance of bones dispersion on surface and at different times of the fossiliferous package formation. In addition, the post-depositional changes of the sediments were important to the vertical dispersion of refitted pieces. Lastly, the confined nature of the pit, the high density of fossils and the slow sedimentation rate favored vertical and horizontal mixture of bones/teeth of different individuals and taxa. The complexity identified in the deposit formation has implications for the study of cave sites, especially with regard to the use of spacial fossils association to subsidize depositional and paleoenvironmental interpretations. (AU) | |
| FAPESP's process: | 09/03753-4 - Formation processes of a fossiliferous pitfall deposit in Gruta Cuvieri (MG): taxonomy, taphonomy and spacial distribution of mammal fossils from the Pleistocene |
| Grantee: | Elver Luiz Mayer |
| Support Opportunities: | Scholarships in Brazil - Master |