formation

Banded iron formation from the Precambrian of Wyoming, USA. (~10.9 cm across at its widest) Banded iron formations, or BIFs, are unusual, dense sedimentary rocks consisting of alternating layers of iron-rich oxides and iron-rich silicates. Most BIFs are Proterozoic in age (although some are Late Archean), and do not form today - they're “extinct”! Many specific varieties of iron formation are known, and some are given special rock names. For example, jaspilite is an attractive reddish & silvery gray banded rock consisting of hematite, red chert (“jasper”), and specular hematite or magnetite. Because of their age, most BIFs have been around long enough to have been subjected to one or more orogenic (mountain-building) events. As such, most BIFs are folded and/or metamorphosed to varying degrees. BIFs are known from around the world, but some of the most famous & extensive BIF deposits are found in the vicinity of North America’s Lake Superior Basin. Many BIFs have economic concentrations of iron and are mined. BIFs are the most important variety of iron ore on Earth. Some iron mines in west-central Wyoming exploit BIFs in the Goldman Meadows Formation, a Mesoarchean unit exposed in the Wind River Range. These rocks have been multiply metamorphosed during the Precambrian. The result of this metamorphism is highly contorted folding and fracturing. The rock shown above is a folded quartz-hematite-limonite meta-BIF. Stratigraphy: iron formation member (probably the upper iron formation member) of the Goldman Meadows Formation, upper Mesoarchean, 2.87 Ga (metamorphosed in the Archean at 2.8 Ga and in the Mesoproterozoic at 1.4 Ga) Geologic context: northwestern flank of the South Pass Greenstone Belt, southern Wind River Range Locality: Atlantic City Iron Mine (open-pit mine; sample possibly collected from tailings piles around the now-flooded pit) (E1/2 of section 26, T30N, R100W, Miners Delight 7.5' USGS topographic quadrangle), South Pass-Atlantic City Mining District, along Rt. 28, southwestern side of South Pass, north of Atlantic City, southwestern Fremont County, west-central Wyoming, USA (mine is at 42° 32' 45" North latitude, 108° 44' 33" West longitude)

This artist's concept shows a celestial body about the size of our moon slamming at great speed into a body the size of Mercury. NASA's Spitzer Space Telescope found evidence that a high-speed collision of this sort occurred a few thousand years ago around a young star, called HD 172555, still in the early stages of planet formation. The star is about 100 light-years from Earth.

Palaeogeographic distribution of late Early and early Late Cretaceous pterosaur assemblages. Taxonomic composition of assemblages shown on Fig. 1. Palaeogeography based on Smith et al. 1994. Abbreviations: 1. Cambridge Greensand, England: 2. Lower Chalk, England: 3. Züümbayan Svita, Khuren-Dukh, Mongolia: 4. Lysaya Gora, Saratov, Russia: 5. Kem Kem red beds, Morocco: 6. Paw Paw Formation, Texas, USA: 7. Lagarcito Formation, San Luis, Argentina: 8. Santana and Crato Formations, Ceara, Brazil: 9. Toolebuc Formation, Queensland, Australia.

Locality map for Australian eurypodan thyreophoran fossils. 1, Stegosaurian? footprint (QM F5701), Walloon Coal Measures, Balgowan Colliery, Balgowan (Bajocian–Bathonian); 2, Minmi paravertebra holotype (QM F10329) (Molnar, 1980), Minmi Member, Bungil Formation (Valanginian–Barremian); 3, Thyreophoran trackways, Broome Sandstone, Dampier Peninsula, Western Australia (Valanginian–Barremian); 4, Ankylosauria indet. (see Barrett et al., 2010) ‘Flat Rocks’ Wonthaggi Formation (upper Hauterivian–Albian); 5, NMV P216739, ‘Lake Copco–Dinosaur Cove’ Eumeralla Formation (middle upper Aptian to lower middle Albian) (Barrett et al., 2010); 6, QM F33286; 7, AM F119849 and AM F35259; 8, Kunbarrasaurus ieversi gen. et sp. nov. (formerly Minmi sp.) (QM F18101); 9, QM F33565 and QM F33566; 10, QM F44324-28. Legend: Dark Green, Toolebuc Formation (late middle–early late Albian); Green, Allaru Formation (upper Albian–(?)lower Cenomanian); Light green, Mackunda Formation (upper Albian–lower Cenomanian); Lightest green, Winton Formation (late Albian–early Turonian).

Original figure caption: .mw-parser-output .smallcaps{font-variant:small-caps}The Middletown Slab covered with the Footprints of Carnivorous Dinosaurs. The tracks are in high relief. Additional notes: Most if not all of these tridactylous (i.e. three-toed) footprints/tracks (but not the actual trackmaker!) are referred to as Grallator or as Grallator-type trace fossils. “High relief” means that these are actually casts of footprints forming a positive relief on the lower surface of the sandstone slab (so-called positive hyporelief). The material that originally formed the mud over which the dinosaurs walked was too friable to be recovered from the quarry in one piece. The slab consists of so called ‘brownstone’ which is the trading name of the sandstone quarried at Middletown, Connecticut. This sandstone belongs to the Lower Jurassic Portland Formation of the Hartford Basin (“Connecticut Valley”) and thus to the upper part of the Newark Supergroup. The trackmakers probably were relatively small ‘primitive’ theropod dinosaurs (coelophysoids) such as Podokesaurus the remains of which were recovered from Lower Jurassic deposits of the Hartford Basin.

A pair of Wendiceratops running through the Oldman formation.

Brachylophosaurus canadensis TMP 1990.104.0001, Oldman Formation, Milk River, Alberta. Original, not cast. At the Royal Tyrrell Museum of Palaeontology.

Brachylophosaurus canadensis TMP 1990.104.0001, Oldman Formation, Milk River, Alberta. Original, not cast. At the Royal Tyrrell Museum of Palaeontology.

Campanian fauna from the Oldman Formation: Wendiceratops, Corythosaurus, Scolosaurus, Chasmosaurus and "Troodon"

Geographic and stratigraphic relationships of the holotype EMK 0012 and the Loki Quarry in northern Montana. (A) Regional relationships between the cross-border paleontological sites in the Oldman and Judith River formations along the Milk River and in Kennedy Coulee in Alberta and Montana. (B) Generalized stratigraphic section in the Kennedy Coulee area modified after Goodwin & Deino (1989) and Rogers, Eberth & Ramezani (2023) with the relationships between the Foremost and Oldman formations in Canada and the Judith River Formation in Montana. Relative placements of important taxa in this area are indicated. Position of 40Ar/39Ar dates originally obtained by Goodwin & Deino (1989) are shown in relation to the new U–Pb CA-ID-TIMS date for KC061517-1 by Ramezani et al. (2022). Bentonite ash beds are only 5 to 7 cm thick so they are exaggerated for clarity. Scale bars delineated in map view are indicated kilometers and in meters stratigraphically.

Brachylophosaurus, Daspletosaurus and Scolosaurus from the Oldman Formation.

Brachylophosaurus canadensis skull (original). From the Oldman Formation, Milk River, Alberta. On display at the Royal Tyrrell Museum, Alberta, Canada.

Brachylophosaurus canadensis (TMP 2005.000.0029), Royal Tyrrell Museum, Drumheller, Alberta, 2025-07-13; cast, Campanian, from the Oldman Formation

Sandstones of the Milk River Formation flank the Milk river at Writing-on-Stone Provincial Park, Alberta.

African locality: 5, Majunga, Maevarano Formation (Campanian): Rahonavis ostromi.

Bryce Canyon geologic map, showing a variety of rock formations in the national park including the Claron Formation, which forms the park’s famous red hoodoos.