Abstract: The deep-water Pindos Basin was characterized by siliceous sedimentation during Jurassic-Cretaceous times. Cretaceous siliceous oceanic red beds, i.e., red cherts and radiolarites 25 to 100 m in thickness, are present in the Katafito Formation (Valanginian-Coniacian), whereas the overlying Upper Cretaceous Platy Limestone Formation is characterized by red and gray pelagic carbonates and turbidites. The Katafito Formation consists of siliceous red claystones, ribbon radiolarites, cherts to marly claystones with an apparent red-green cyclicity, silicified mud, and radiolarian-sand turbidites. Sedimentation rates vary between 0.5 and 1.5 mm/kyr. In the siliceous CORB succession, five green to black levels have been recognized, composed of greenish claystones, mudstone turbidites, green to black layered or nodular cherts, and distinct black shales. These green to black intervals can be correlated to oceanic anoxic events, namely, the Late Valanginian Weissert Event, a latest Barremian event, and the Early Aptian OAE 1a, the Late Aptian to early Albian OAE 1b, and the Late Albian OAE 1c and OAE 1d events. From the Middle Cenomanian onwards, turbidites and mass-flow deposits increase in number, but red radiolarites remain the normal background sedimentation in the Pindos Basin. The overlying red marlstones and limestones of the basal Platy Limestone Formation, starting diachronously in the Coniacian to Santonian, record a shallowing of the basin to above the calcite compensation depth and again an increase in detrital carbonate input. The siliceous red beds of the Pindos Basin and other basins in the eastern Mediterranean indicate a long-term record of oxic sedimentation during the Early Cretaceous up to the Coniacian that was punctuated only by short-term anoxia during widespread oceanic anoxic events.

Abstract A transect of three holes drilled across the Blake Nose, western North Atlantic Ocean, retrieved cores of black shale facies related to the Albian Oceanic Anoxic Events (OAE) 1b and 1d. Sedimentary organic matter (SOM) recovered from Ocean Drilling Program Hole 1049A from the eastern end of the transect showed that before black shale facies deposition organic matter preservation was a Type III–IV SOM. Petrography reveals that this SOM is composed mostly of degraded algal debris, amorphous SOM and a minor component of Type III–IV terrestrial SOM, mostly detroinertinite. When black shale facies deposition commenced, the geochemical character of the SOM changed from a relatively oxygen-rich Type III–IV to relatively hydrogen-rich Type II. Petrography, biomarker and organic carbon isotopic data indicate marine and terrestrial SOM sources that do not appear to change during the transition from light-grey calcareous ooze to the black shale facies. Black shale subfacies layers alternate from laminated to homogeneous. Some of the laminated and the poorly laminated to homogeneous layers are organic carbon and hydrogen rich as well, suggesting that at least two SOM depositional processes are influencing the black shale facies. The laminated beds reflect deposition in a low sedimentation rate (6m Ma −1 ) environment with SOM derived mostly from gravity settling from the overlying water into sometimes dysoxic bottom water. The source of this high hydrogen content SOM is problematic because before black shale deposition, the marine SOM supplied to the site is geochemically a Type III–IV. A clue to the source of the H-rich SOM may be the interlayering of relatively homogeneous ooze layers that have a widely variable SOM content and quality. These relatively thick, sometimes subtly graded, sediment layers are thought to be deposited from a Type II SOM-enriched sediment suspension generated by turbidites or direct turbidite deposition.