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Abstract: Upper Tithonian–Berriasian pelagic carbonates in the Central Western Carpathians, Tatra Mts (southern Poland), with well-established bio- and magnetostratigraphy, provide excellent possibilities of testing magnetic and geochemical methods as proxies of palaeoenvironmental changes in the Western Tethys at the Jurassic/Cretaceous boundary. Magnetic susceptibility (MS), field spectral gamma-ray (GRS) as well as CaCO3, total organic carbon (TOC), and elemental analyzes were performed in the Pośrednie III section. MS reveals very good negative correlation with CaCO3 content as well as positive correlation with Al, Zr, Ti and other lithogenic elements and therefore it might be interpreted as a proxy of a detrital input into the basin. Abrupt MS variations correlate well with relative sea-level changes and indicate regressive intervals (MS highs) in the upper Tithonian/lowermost Berriasian (M20r to M19n2n) and upper Berriasian (M16n) and transgressive interval (MS low) in the lower to middle Berriasian (M18r to M17r). Long-term MS variations might be linked to a palaeoclimatic-controlled enhanced continental runoff. Geochemical data (P, Th/U, Mn, Cd, Ni, Mo and TOC content) point to a productivity increase and a slight oxygen deficiency in the lower and middle Berriasian, which corresponds to MS low values and typical calpionellid limestone sedimentation. Timing of major palaeoenvironmental turnovers might be correlated also with general palaeoclimatic trends in the Western Tethys and Western Europe: cooling in the late Tithonian followed by a temperature increase throughout the Berriasian and an important humidity increase in the middle Berriasian (M17n). [Copyright &y& Elsevier]

Carbon and silicon cycles at the Earth surface are linked to long-term variations of atmospheric CO 2 and oceanic primary production. In these cycles, the river-sea interface is considered a biogeochemical hotspot, and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments. In contrast, periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep-sea via submarine canyons and accumulation in deep-sea fans. Here, we calculate present-day mass balances for organic carbon (OC) and amorphous silica (aSi) in the terminal lobe complex of the Congo River deep-sea fan as an analogue for glacial periods. We show that this lobe complex constitutes a megasink with the current accumulation of 18 and 35% of the OC and aSi river input, respectively. This increases the estimates of organic carbon burial by 19% in the South Atlantic Ocean in a zone representing less than 0.01% of the basin. These megasinks might have played a role in carbon trapping in oceanic sediments during glacial times. • Sediments located at the termination of Congo Canyon are a megasink of organic carbon (0.35 TgC/yr) and aSi (0.11 TgSi/yr). • These sediments store in the deep-sea at 5 km depth 18 and 35% of Congo River OC and amorphous silica inputs, respectively. • OC burial in these sediments increases OC burial in the South Atlantic deep basin (>3000m) by 19% for a surface area <0.01%. • Burial efficiencies in this megasink are 85% for OC and 73% for aSi. [ABSTRACT FROM AUTHOR]