LATE BARREMIAN TO EARLY APTIAN PALEOENVIRONMENTAL CONDITIONS RECORDED IN THE SEDIMENTOLOGICAL AND GEOCHEMICAL RECORDS OF THE LO PUI SECTION, NE SPAIN

The Lo Pui section (late Barremian to lower Aptian) of the Organyá basin, south-central Spanish Pyrenees, comprises deposits associated with extensional tectonism followed by strong subsidence resulting in the development and accumulation of carbonate platforms and deeper-water hemipelagic sediments. This study uses high-resolution microfacies analyses (SEM, EDS) and geochemical analyses (TIC, TOC, δ¹³C_–org, major elements (Al, Si, Fe, Ti) and V/V+Ni, V/Cr, Ni/Co, U/Th) in order to define the influence of local factors in the paleoenvironmental evolution of the semi-enclosed basin prior to the onset of OAE-1a.

Major elements indicate punctuate intensified influx of continental runoff from the terrestrial environment into the marine system. V/V+Ni concurrently with the V/Cr ratios versus Ni/Co, as well as U/Th ratio yield values consistent with the occurrence of reducing conditions within the suboxic/dysoxic regions. Although, eutrophication of the water column may have taken place in the basin during this time interval, the obtained results do not support the occurrence of anoxic conditions. δ¹³C in the organic fraction indicates fluctuations in the isotopic composition of the marine reservoir possibly induced by enhanced primary productivity.

The integrated results imply that the physiography of the basin, jointly with the relative increase in the topography of the terrestrial environment at that time, led to conditions that exacerbated the intensity of local forcing factors (intensified runoff, higher biological productivity, reduced oceanic circulation) causing the development of intermittent stressful oxygen-poor environments in the Organyá basin.