Groundwater occurs in silty to sandy layers of the alluvial sediments. Flysch consists of repeated sedimentary cycles with upwards fining of the sediments. Alluvial placers are those formed in river or stream sediments. Subfossils are often found in depositionary environments, such as lake sediments, oceanic sediments, and soils. Subsequent erosion stripped the granite of the overlying sediments and the softer adjacent schist. These sediments include igneous crust, turbidite sediments, and pelagic sediments. Bacteria that live in detrital sediments create and cycle nutrients and biominerals. Traditionally prospecting relied on direct observation of mineralization in rock outcrops or in sediments. This results from differences in isotopic ratios of sediments and rocks within the different oceans. The Quaternary lavas are directly on the Jurassic sediments. These differences resulted in different patterns of basin formation and transport of sediments. The effect of increased sediments loads on aquatic ecosystems can be catastrophic. This occurred following uplift and erosion of any earlier sediments from the Proterozoic basement rocks. Distributions of organic molecules in marine sediments reflect temperature. Conodonts were present in Triassic marine sediments.