Comparative geochemistry of quaternary carbonaceous sediments from the continental slope of the Baja California and the miocene monterey formation

Resumo

The geochemistry of Upper Quaternary organic-rich (C_org 3.7–10.0%) sediments recovered by the 40-m-long Core MD02-2508 from the upper continental slope of Baja California is compared to the chemical composition of sedimentary rocks from the Miocene Monterey Formation, California. It is ascertained that concentrations of most macroelements (Al, Ti, Mg, K, Fe, M, S, C_org) and many microelements, including chalcophiles Ag, As, Mo, Sb, Se, Zn, along with some others (U, Co, Ni, Y, and REE) are nearly equal in both types of sediments. In addition, concentrations of most microelements in both types of sediments are close, to the average values common for the worldwide carbonaceous black shales irrespective of their lithology and age, indicating a stable influence of organic matter on their concentration during sedimentation and early digenesis.