Chemical taphonomy and preservation modes of Jurassic spinicaudatans from Patagonia: a chemometric approach

Spinicaudatans (‘clam shrimps’) are small branchiopod crustaceans enclosed in a chitinous bivalved carapace that is often the only preserved element in the fossil record. However, few studies have analyzed the preservation of these carapaces, which have been found in continental facies from the Devonian to the present. The aim of this study was to contribute to a better understanding of the chemical preservation of fossil spinicaudatan carapaces, and focused on spinicaudatan carapaces of the Cañadón Asfalto Formation from the Jurassic of Argentina. Semi-quantitative energy-dispersive X-ray spectrometry (EDS) analysis provided elemental composition data that were interpreted using principal component analysis (PCA). The results showed a complex chemical mode of preservation for spinicaudatan carapaces. In some parts, EDS spectra of the specimens exhibits peaks of calcium, phosphorous, aluminum and fluorine, representing the retention of original carapace material with some diagenetic r...