MECHANISMS OF ENHANCED ORGANIC CARBON SEQUESTRATION DURING THE EARLY APTIAN IN THE RESTRICTED ORGANYA BASIN

Regional physiographic conditions have been invoked as a causal factor for enhanced organic matter sequestration in various restricted marine basins and epicontinental seas during the Barremian-Aptian transition. Here we present a multiproxy study to assess the conditions that led to enhanced OM preservation in the late - early Aptian as compared to the late Barremian - earliest Aptian interval in the restricted Organyà Basin. TOC values of up to 5.0%, concurrent with temporal positive excursions in δ¹³C_org, attest to higher primary productivity and organic carbon burial. Phosphorous and Iron concentrations normalized with respect to Aluminum confirm nutrient rich waters, and temporal enrichment of redox-sensitive trace elements (Zn, V, Ni, Cr, Cu, Mo, U) reveal the occurrence of oxygen-deprived conditions with intervals of anoxia.

The results suggest that the effects of local physiographic conditions in the Organyà Basin superimposed on global greenhouse factors became more prominent in the early Aptian, and further accentuated existing oxygen deficiency in the basin. Pronounced stratification of the water column, high bio-productivity, and intense oxygen depletion are considered to be responsible for higher OM preservation during the early Aptian relative to the late Barremian - earliest Aptian transition.