Albian Anaerobic environment Aptian C-13/C-12 Carbon Clastic rocks Cretaceous Currents Deep Sea Drilling Project Depositional environment Grain size Hemipelagic environment High-resolution methods IPOD Isotope ratios Isotopes Laminations Lower Cretaceous Marine environment Mesozoic Paleoenvironment Pelagic environment Planar bedding structures Sandstone Sedimentary rocks Sedimentary structures Siltstone Stable isotopes Turbidity currents