Boreskov

PP‐4BIOCHEMICAL REACTION OF EARLY PALEOZOIC BRACHIOPODSON GEOBIOLOGYCAL EVENTS IN THE NORTH URALS PALEOBASINBeznosova T.M., Shanina S.N.Institute of Geology, 54, Pervomaiskaya st., 167982, Syktyvkar, RussiaIn the European Northeast brachiopods are one of the most widespread and wellstudied faunal groups, which continuously occur through in various facial sediments of EarlyPaleozoic [1]. In connection with brachiopods served as a basis for defining the biochemicalresponse of these organisms to external environmental changes and compositional changesof amino acids in brachiopod shells and host rocks through the Late Ordovician, Silurian, andEarly Devonian.The rock samples with brachiopod shells were collected from Silurian, Ordovician, andDevonian deposits of the North Urals, Subpolar Urals and Chernyshev Uplift. The samples arecharacterized by well defined stratigraphic and facies positions.The amino acid contents are highly variable in shells (0.04 to 0.19 mg/g of the shell) andpractically stable in carbonate rocks (0.03– 0.06 mg/g of the rock). In samples significantfluctuations of individual amino acid composition are observed that is quite characteristic forPaleozoic shells [2, 3]. Among individual amino acids are usually dominate glycine, serine,glutamic acid and leucine, while threonine, proline, and valine often are absent. The samplesalso contain D‐alloisoleucine, which represents an amino acid forming under hightemperatures.The biochemical study of brachiopod shells reveals changes in amino acidconcentrations: increase across the Ordovician–Silurian boundary (from 40 μg/g in theOrdovician to 50–80 μg/g in the early Llandovery (Rhuddanian)); decrease to 40 μg/g at theend of late Llandovery; abrupt growth to 100–190 μg/g in the Wenlock; reduction of valuesto 40 μg/g in the Ludlov and Pridoli; and increase up to 80 μg/g in the Early Devonian. Themaximum of amino acids concentration exceeding 100 μg/g is fixed in samples selecteddirectly above a level of paleontologically proved Llandoveri–Wenlock boundary [4].As all the investigated samples are characterized by practically the same catageneticheating level, differences in the concentrations of amino acids in brachiopod shells from asingle stratigraphic interval may be explained by their different burial conditions. Forexample, the protein component in shells from the Wenlock and Early Devonian appeared to137