22 articles
Balang Formation
Balang Formation (杷榔组), Cambrian Stage 3-4 shale unit in Guizhou and Hunan, South China, host of the Burgess Shale-type Balang Biota, transitional between the Chengjiang and Kaili biotas, with oryctocephalid trilobites, chancelloriids, and the Huayuan biota.
Black shale
Black shale is a dark mudrock rich in organic matter and pyrite, defined by more than 1% total organic carbon, that can generate oil and natural gas.
Bradgate Formation
Bradgate Formation: Ediacaran volcaniclastic unit of the Maplewell Group, Charnwood Forest, Leicestershire, at least 175 m thick, base dated 563 ± 1.9 Ma; hosts Charnia masoni and most Charnwood Ediacaran fossils.
Breccia
Breccia is a clastic rock composed of angular fragments larger than 2 mm held by mineral cement, its sharp-edged clasts distinguishing it from conglomerate, whose clasts are rounded by transport.
Clastic rock
A clastic rock is a sedimentary rock composed of clasts, fragments of pre-existing rock or mineral grains, bound by compaction and cementation, and classified mainly by grain size.
Cooper Canyon Formation
Cooper Canyon Formation, uppermost formation of the Dockum Group (Upper Triassic, Norian, 228-209 Ma) in West Texas; reddish mudstone and sandstone lacustrine unit hosting the Post Quarry vertebrate fauna, distinct from the Australian Cooper Basin.
Diamictite
Diamictite is a lithified, poorly sorted siliciclastic sedimentary rock with a wide clast size range and no fixed origin; its widespread deposits record ancient glaciations such as the Cryogenian Snowball Earth episodes.
El Rosario Formation
El Rosario Formation (Formación Rosario), Late Cretaceous Campanian-Maastrichtian marine to non-marine clastic unit on the Pacific coast of Baja California, Mexico; type section near El Rosario town; includes deep-marine turbidites and rich fossils.
Evaporite
An evaporite is a nonclastic sedimentary rock formed when minerals precipitate from saline water as it evaporates, typically including gypsum, anhydrite, and halite (rock salt).
Flysch
Flysch is a sedimentary facies of thin, regularly alternating sandstone, shale, and limestone beds deposited in deep marine basins during early mountain building; its turbidite record contrasts with molasse.
Greywacke
Greywacke, also spelled graywacke (German Grauwacke), is a dark gray, hard, poorly sorted sandstone deposited by underwater density currents in deep ocean water near mountain ranges.
itabirite
Itabirite is a laminated, metamorphosed banded iron formation in Minas Gerais, Brazil, named there in 1822, composed of quartz with hematite or magnetite and hosting most Brazilian iron ore.
Maevarano Formation
Maevarano Formation: Late Cretaceous (Maastrichtian, 72.1-66 Ma) fossil-rich rock unit in Madagascar's Mahajanga Basin, near Berivotra; source of Majungasaurus, Rapetosaurus, Rahonavis, Beelzebufo; distinct from the Maevarano Suite granites.
Microbialite
A microbialite is an organosedimentary deposit that accretes through interaction between benthic microbial communities and sediments, a term introduced by Burne and Moore in 1987 that includes stromatolites and thrombolites.
middle Kaub Formation
Middle Kaub Formation: clay-rich middle part of the Kaub Formation (Lower Emsian, Lower Devonian) in the Hunsrück, Germany; five members, laminated slates with Chondrites, source of the Bundenbach Hunsrück Slate fossils.
Mudstone
Mudstone is a fine-grained sedimentary rock of hardened mud, essentially shale without its fine lamination or ability to split into thin flakes, making up much of the sedimentary record.
Poleta Formation
The Poleta Formation is an Early Cambrian sedimentary unit of limestone and siltstone exposed in the White and Inyo Mountains of California and western Nevada, named by C. A. Nelson in 1962.
Radiolarite
Radiolarite is a hard siliceous sedimentary rock made of radiolarian skeletons, the lithified equivalent of radiolarian ooze, and a raw material for prehistoric stone tools.
Siltstone
Siltstone is a clastic sedimentary rock made predominantly of silt-sized grains, defined by the USGS as indurated silt with the texture of shale but lacking its fine lamination or fissility, and finer than sandstone.
Tuffaceous sandstone
Tuffaceous sandstone is a sand-grade sedimentary rock containing 25% to 75% volcanic particles, chiefly pyroclastic material such as volcanic glass and ash, mixed with ordinary sand grains, intermediate between sandstone and tuff.
Wahweap Formation
Wahweap Formation: Upper Cretaceous (Campanian, about 82.2 to 77.3 Ma) sandstone and mudstone unit on Utah's Kaiparowits Plateau, overlying the Straight Cliffs Formation, with Diabloceratops, Lythronax, and early hadrosaur fossils.
Wheeler Shale
Wheeler Shale, Middle Cambrian shale and limestone unit in the House Range, Millard County, Utah, named by Walcott in 1908; famous for Elrathia kingii trilobites and Burgess Shale-type soft-bodied fossil preservation.