do Ritter, M. N., Francischini H., Kuhn L. A., da Luz N. C., Michels F. H., de Morais A. L. M., Paim P. A. V., Xavier P. L. A., & de Francesco C. G.
(2016).
El sesgo del operador en la replicabilidad de los estudios tafonómicos comparativos.
Revista Brasileira de Paleontologia. 19, 449–464., jan, Number 3: Sociedade Brasileira de Paleontologia
Abstractn/a
Ritter, M. D. N., Erthal F., & Coimbra J. C.
(2019).
Depth as an overarching environmental variable modulating preservation potential and temporal resolution of shelly taphofacies.
Lethaia. 52, 44-56., Number 1: Blackwell Publishing Ltd
Abstractcited By 0
In the marine realm, the interpretation of taphofacies relies heavily on how oceanographic and sedimentary conditions affect the preservation state of fossils. Several taphonomic variables either covary with depth or are directly influenced by depth. Facies-level factors rather than broad, basin-scale parameters influence the taphonomic profile of mollusc death assemblages according to actualistic and experimental evidence. To determine the possible relation between depth and the taphonomic conditions of multiple species of bivalve remains, we used seven samples gathered over a comprehensive bathymetric gradient (from 7 to 150 m below mean sea level; topmost 10- to 20-cm layer, roughly corresponding to the taphonomically active zone). We selected samples from predominantly muddy facies on the southern Brazilian shelf (SBS). The taphonomic damage profile (TDP) was measured using site samples based on a standard taphonomic analysis (categorical scoring system) of shells and fragments larger than 4 mm, to identify site damage patterns. Restricting the sedimentary grain size (samples from fine sediments) enabled the determination of the variation in damage with depth among the samples. Constrained analysis of proximities (CAP) revealed that up to 46% of the taphonomic variation observed was related to variation in depth (with approximately 28% unexplained by environmental factors). Part of the unexplained fraction was due to the effect of temporal mixing, which is predictable along large-scale patches but is inversely linked to the TDP. Our results show that taphonomic analysis, considering large spatial scales in recent environments, can explain the variations present in shell beds that formed during distinct time periods of the evolution of a Quaternary sedimentary basin. © 2018 Lethaia Foundation. Published by John Wiley & Sons Ltd
do Ritter, M. N.
(2018).
{R script used for the analysis of spatio-temporal patterns of fossil molluscs on the continental shelf of southern Brazil}.
: Universidade Federal do Rio Grande do Sul, Porto Alegre
Abstractn/a
The R codes provide Bayesian model fitting procedures for AAR-\^{}14\^{}C datasets. These codes are updated versions of the analytical scripts published by Allen et al. (2013). \\ Based on the ages derived from the models fitted, it is possible then to account for the time-averaging (temporal resolution of the fossil record). The time-averaging estimates are based on empirical posterior distributions, accounting for dating uncertainty, as in Ritter et al. (2017).\İn addition, the R codes implements the figures produced both the cited dissertation and its derived manuscripts, like the best models fitted, age-frequency distribuitions (Histograms), its relations with sea-level oscilation in the Southern Brazilian shelf etc.
Ritter, M. D. N., Erthal F., Kosnik M., Coimbra J. C., & Kaufman D. S.
(2017).
Spatial variation in the temporal resolution of subtropical shallow-water molluscan death assemblages.
Palaios. 32, 572-583., Number 9: SEPM Society for Sedimentary Geology
Abstractcited By 4
Fossil assemblages are expected to be time-averaged as a result of biological and physical processes that mix skeletal remains. Our quantitative understanding of time-averaging derives primarily from actualistic studies, in which direct numerical dating of individual specimens is used to assess the scale and structure of age mixing in death assemblages (incipient fossil assemblages). Here we examine the age, and the time-averaging of Mactra shells (Bivalvia: Mollusca) gathered from surface mixed siliciclastic-bioclastic sands at three sites on a passive-margin subtropical shelf (the Southern Brazilian Shelf; ∼ 33°S). Sixty Mactra specimens were individually dated using amino acid racemization (AAR) calibrated using radiocarbon ages (n=15). The time-averaging and the total age variability was based on a Bayesian approach that integrates the estimation errors and uncertainties derived from the posterior distribution associated with the AAR calibration average model. The 14C-calibrated AAR ages, pooled across all three sites, are strongly right-skewed with 97% of the individual mollusk shell age estimates ranging from 0 to 6 cal kyr BP. The magnitude of time-averaging varied inversely with the water depth, from < 15 yr at the deepest site (21 m) up to 1020-1250 yr at the shallowest site (7 m). The substantial variation in the temporal resolution across nearby sites, which are located in a seemingly homogenous depositional setting, indicates the presence of notable (if cryptic) spatial heterogeneities in local sedimentation, production, and exhumation, all increasing with water depth. Copyright © 2017, SEPM (Society for Sedimentary Geology).