Taphonomy of Recent Bioclastic Deposits from the Southern Brazil Shelf: Stratigraphic Potential

Citation:
Erthal, F., & RITTER M. A. T. I. A. S. D. O. N. A. S. C. I. M. E. N. T. O. (2020).  Taphonomy of Recent Bioclastic Deposits from the Southern Brazil Shelf: Stratigraphic Potential. (Martínez, Sergio, Rojas, Alejandra, Cabrera, Fernanda, Ed.).Actualistic Taphonomy in South America. 1 - 16., 2020, Cham: Springer International Publishing

Abstract:

In the Southern Brazil ShelfSouthern Brazil Shelf (SBS), surface bioclastic concentrationsBioclastic concentrations are associated with putative paleo-shorelines formed where wave ravinement surfaces are probably present. From the late Last Glacial Maximum, the SBS can be considered a sediment-starved passive margin continental shelf, with its morphostructural development fairly known. There, fourteen molluscan shell samples from near shelf-break deposits (“distal shell-rich”), eleven from proximal, low depth bioclastic deposits (“proximal shell-rich”) and ten samples from sandy substrate (“shell-poor”) were evaluated for taphonomic damage accordingly to updated protocols. Multivariate statistical analysis showed significant differences between the three groups of shelly samples. Low-intensity damage states (such as natural bright and ornamentation) dominate samples from the distal shell-rich deposit, whereas the inverse occurs in the proximal deposit (samples from the shell-poor locations present an intermediate damage pattern). This pattern is consistent either with onlap/toplap and backlap shell bedShell bed formation, according to characteristics determined in the literature. The condition of these three areas may reflect degrees of exposure at the taphonomically-active zone, the magnitude of time averagingTime-averaging and duration of shell accumulation, and even the lack of shelf accommodation space, which in turn is related to glacioeustatic sea-level oscillations.

Notes:

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