Application of raman spectroscopy for the study of preservation of fossil clam shrimps

摘要: In this study, carapaces of the fossil clam shrimp Eosolimnadiopsis? santacrucensis Gallego from the La Matilde Formation (Middle Jurassic) at Meseta Chica and Puesto Raspuzzi localities (Gran Bajo de San Julián, Santa Cruz province, Argentina), were analyzed using RAMAN spectroscopy. Clam shrimps, also known as 'conchostracans' represent one of the oldest crustacean lineages, which dates back to the Lower Devonian and survived to the present day. They are small organisms, with a short and laterally compressed body that is included within a chitinous and mineralized carapace which is the only component usually found in the fossil record. The carapace morphologically consists of two layers; an outer one, composed of proteins, lipids and calcium salts; and an inner one, multilamellar, mainly of chitin. However, few studies have been carried out regarding the chemical preservation of the organic carapace. Studied materials are deposited in the Paleozoology Section of the Paleontological Collections ?Dr. Rafael Herbst? from the Universidad Nacional del Nordeste (Corrientes, Argentina) under the acronym CTES-PZ. The Raman spectra were obtained by the RAMAN Thermo-Fischer DXR microscope, the parameters used in the analyzes were: 780 nm diode laser, power of 10.0 mW with a slit aperture of 25 μm and exposure time of 70 s. The results of the studied samples from Meseta Chica locality, revealed different percentages of amorphous carbon, more ordered and disordered graphitic that is expressed in the G (~ 1600 cm-1) and D (~ 1360 cm-1) bands. For the G band, a center at 1600 +/- 10 was used and the settings …