12 depositional sedimentary environments lab | Geology homework help
- Beach - high energy environment dominated by medium- to course- grained sandstone, well- sorted and rounded; horizontal laminations, low-angle cross-bedding, wave ripple marks are most abundant; fossils are rare and typically broken into fragments; sand body is elongate in shape and trends parallel to shore. 2. Tidal flat – so named due to the tide coming in and receding in this relatively flat region. It will have inter-bedded sandstone, siltstone and shale, with grain size increasing in a seaward direction; cross-bedding (some large-scale), wave and current ripple marks, mud cracks, scour or channel surfaces, and animal burrows, tracks and trails are common; fossils (marine) are rare to abundant; wedge to irregular sheet shape.
III. OPEN MARINE
A. Pelagic- These environments are within the ocean water mass; thus, they don’t have characteristic features preserved in the geologic record. Organisms which live in these environments fall to the ocean bottom upon death and become part of the record of one of the benthic environments listed: 1. Neritic-depth to sea-floor less than 200 meters 2. Oceanic- depth to sea-floor greater than 200 meters B. Benthic (bottom environments) 1. Shallow marine (Shelf) - sandstone, siltstone, limestone and shale interbedded, sandstone composed predominantly of quartz but with some marine fossil fragments; cross- bedding (some large-scale), ripple marks, and marine burrows, tracks and trails common; marine fossils locally abundant; widespread sheet-like or blanket shape. Water depths are typically less than 200 m.