Biotic and Abiotic Controls on Black Shale Diagenesis and Redistribution of Trace Elements

Abstract

The Llanvirn-Llandeilo/Caradoc black shales of southwest Wales, U.K. have undergone a multistage diagenetic history (Lev et al. , 1998). The paragenetic sequence from these rocks requires early and late diagenetic events that have redistributed trace and major elements and left an overprint on the Sm-Nd and U-Pb whole rock isotopic systems. The types of reactions essential to produce these mineralogic and geochemical changes require both biotic and late abiotic processes. The relative importance and timing of these processes can be evaluated by examining their net effect on the mineralogy and geochemistry of the whole rock P a r a g e n e t i c s e q u e n c e o f t h e L l a n v i r n L l a n d e i l o C a r a d o c b lack shales