The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian.
The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 190.8 ± 1.5 Ma and 182.7 ± 1.5 Ma. The Pliensbachian is preceded by the Sinemurian and followed by the Toarcian.
The Navajo Sandstone is a geological formation in the Glen Canyon Group that is spread across the U.S. states of southern Nevada, northern Arizona, northwest Colorado, and Utah as part of the Colorado Plateau province of the United States.
The Kota Formation is a geological formation in India. The precise age of Kota Formation are uncertain, but it dates from the Early to Middle Jurassic, and is split into a Lower Member and Upper Member. The lower member is thought to be Hettangian-Pliensbachian. While the upper unit is thought to be Toarcian, but may possibly extend into the Aalenian. It conformably overlies the Dharmaram Formation which is Late Triassic to earliest Jurassic and is unconformably overlain by the Early Cretaceous Gangapur Formation. The lower member is approximately 100 m thick while the upper member is 490 m thick. Both subunits primarily consist of mudstone and sandstone, but near the base of the upper unit there is a 20-30 metre thick succession of limestone deposited in a freshwater setting.
The Fernie Formation is a stratigraphic unit of Jurassic age. It is present in the western part of the Western Canada Sedimentary Basin in western Alberta and northeastern British Columbia. It takes its name from the town of Fernie, British Columbia, and was first defined by W.W. Leach in 1914.
The Hasle Formation is a geologic formation on the island on Bornholm, Denmark. It is of early to late Pliensbachian age. Vertebrate fossils have been uncovered from this formation. The type section of the formation is found at the south of the costal Hasle Town, and it is composed by rusty yellow to brownish siltstones and very fine-grained sandstones. The southernmost arch, Hvjdoddebuen, is not as fossil-bearing as the type unit in Hasle. The formation can be separated in two different petrographic types: type 1 sandstones are friable with layers and lenses of concretionary siderite and type 2 well-cemented sandstones. Both types where deposited in a relatively high-energy marine environment with a diagenetic pattern that demonstrates a close relation to various phases of subsidence and uplift in the tectonically unstable Fennoscandian Border Zone. Most of it´s deposition happened on a storm-dominated shoreface, with the exposed parts deposited in an open marine shelf within 1–2 km distance from the fault-controlled coastlines. However, recent works have recovered terrestrial fauna from it, including a footprint, suggesting easterly winds and low tide could have exposed the inner parts of the upper shoreface, and create long-lasting Floodplain-type environments. Field works since 1984 have shown a mostly hummocky cross-stratified deposition, with great complexity of the sediments that suggests very complicated and variable flow conditions, with Megaripples derived from storm events. Storms were frequent and the coastline faced a wide epeiric sea with a fetch towards the west of possibly 1000 kilometers. The Jamesoni–Ibex Chronozone in the Central European Basin represents a clear sea Transgression, due to the apperance of ammonites from Thuringia and southern Lower Saxony, showing a full marine ingression towards the west. This rise in the sea level is also measured in the north, as is proven by the presence of Uptonia jamesoni in Kurremölla and Beaniceras centaurus plus Phricodoceras taylori on the Hasle Formation. The whole Hasle Sandstones are a result of this rise in the sea level, where the marine sediments cover the deltaic layers of the Rønne Formation. The rise in the sea level is observed on palynology, as on the Hasle Formation Nannoceratopsis senex (Dinoflajellate) and Mendicodinium reticulaturn appear, indicating a transition from paralic and restricted marine to fully marine.
The Talkeetna Formation is a geologic formation in Alaska. It preserves fossils dating back to the Early Jurassic period.
The Drzewica Formation is a geologic formation in Szydłowiec, Poland. It is Pliensbachian in age. Vertebrate fossils have been uncovered from this formation, including dinosaur tracks. The Drzewica Formation is part of the Depositional sequence IV-VII of the late lower Jurassic Polish Basin, with the IV showing the presence of local Alluvial deposits, with possible meandriform deposition origin, dominated in Jagodne and Szydłowiec, while delta system occurred through the zone of the modern Budki. The sequence V shows a reduction of the erosion in the Zychorzyn borehole of the Drzewica Formation, showing changes on the extension of the marine facies, where upper deposits change from Alluvial to Deltaic-Seashore depositional settings. VI-VII facies were recovered on the Brody-Lubienia borehole, with a lower part exposed on the village of Śmiłów that shows a small fall of the Sea level. The stathigraphic setting of the dinosaur tracks reported from the formation suggest a Seashore or Deltaic barrier. Body fossils reported include bivalves, palynology, fossil trunks, roots. Trunks of coniferous wood, especially Cheirolepidiaceae and Araucariaceae trees show the occurrence of vast coniferous forests around the tracksite. The association of forests and dinosaur megafauna on the Pliensbachian suggests also a colder and specially dry ecosystem. Drzewica deposits where in part to be a gigantic shore barrel, setting at the time where the Polish basin sea was at its lowest point. Other related units are Fjerritslev or Gassum Formation, Hasle & Sorthat Formation (Bornholm), upper Neringa Formation (Lithuania). Abandoned informal units in Poland: upper Sawêcin beds, Wieluñ series or Bronów series.
The Kandreho Formation is an Early Jurassic geological formation of the Mahajanga Basin of Madagascar. The marly limestones of the formation were deposited in a subtidal lagoonal environment. The formation overlies the Bouleiceras and Spiriferina beds of the early Toarcian and has been correlated to the Marrat Formation of Saudi Arabia. Fossils of the marine crocodylian Andrianavoay as well as bivalves and the ammonite Nejdia have been found in the formation. The name Kandreho Formation was proposed by Geiger in 2004.
The Mawson Formation is a geological formation in Antarctica, dating to roughly between 185-181 million years ago and covering the Pliensbachian-Toarcian stages of the Jurassic Period in the Mesozoic Era. Vertebrate remains are known from the formation.
The Ciechocinek Formation, formerly known in Germany as the Green Series is a Jurassic geologic formation that extends across the Baltic coast, from Grimmen, Germany, to Nida, Lithuania, with its major sequence on Poland and a few boreholes on Kaliningrad. Dinosaur remains are among the fossils that have been recovered from the formation, not yet been allocated to a specific genus. The layers assigned to the formation are a group of sediments that differ from the those of the Posidonia Shale and other Toarcian formations of Europe. Most of the sediments of the Polish realm come from deltaic, fluvial and marine deposits. In the Polish realm there is also an abundance of siderite, attributed to mixed saline and marine action, with the rounding off of some due to transport by freshwater or sea currents. Its main equivalents are the Posidonia Shale, upper part of the Rydeback Member, Rya Formation, the Fjerritslev Formation, the Bagå Formation (Bornholm) or the Lava Formation (Lithuania). There are also coeval abandoned informal units in Poland: Gryfice Beds, Lower Łysiec beds, or the "Estheria series".
The Azilal Formation, also known as Toundute Continental Series and Wazzant Formation, is a geological unit in the Azilal & Ouarzazate provinces of the High Atlas of Morocco, that cover the early Toarcian to early Aalenian stages of the Jurassic Period. It is a terrestrial deposit which overlies marine dolomites of equivalent age to the Budoš Limestone of Montenegro or the Marne di Monte Serrone of Italy. Dinosaur remains, such the sauropod Tazoudasaurus and the basal ceratosaur Berberosaurus are known from the unit, along with several undescribed genera. The Units inside the group have been considered individual on the past, being a division of the so-called "Couches rouges", and subdivided by a supposed geological scale. The strata of the group extends towards the Central High Atlas, covering different anticlines, and topographic accidents along the range of the Mountains. Although new studies have suggested that the strata is coeval in age, and should be referred to as a unique unit. The Group is believed to have been a mostly deltaic, and river channels filled a succession of seashore and inland environments, covering the late Liassic coast of modern northern Africa. Based on observed halokinetic strata, the Tazoult Ridge evolved as a Salt Wall forming a 20 km long NE-SW trending structural and sedimentary high for at least 20 million years, between Pliensbachian-Bajocian periods. This emerged small landmass generated a great local diapir, with continuous Diapirism until the end of the Aalenian.
The Krempachy Marl Formation is a geological formation in Poland and Slovakia, dating to about 179 million years ago, and covering the middle Toarcian stage of the Jurassic Period. It is among the most important formations of the Toarcian boundary on the Carpathian realm, being the regional equivalent of the Posidonia Shale.
The Sorthat Formation is a geologic formation on the island on Bornholm, Denmark. It is of latest Pliensbachian-Late Toarcian age. Plant fossils have been recovered from the formation, along with several traces of invertebrate animals. The Sorthat Formation is overlain by fluvial to lacustrine gravels, along with sands and clay along with parts covered by coal beds, that are part of the Aalenian-Bathonian Bagå Formation. In fact the Sorthat Formation was included on most of 80s-90s studies as the lowermost part of the Bagå Formation, recovering the latest Pliensbachian to lower Aalenian boundary, that was dismissed after comparing the geology of the two. The Sorthat strata recover a mostly marginal deltaic to marine unit, where large streams fluctuated to the east where a large river system was established at the start of the Toarcian. At the northwest the local Vulcanism, that started on the lower Pliensbachian, extended along the North Sea and mostly from southern Sweden. At this time, the Central Skåne Volcanic Province and the Egersund Basin expulsed most of their strata, with influences on the local tectonics. The Egersund Basin has abundant fresh porphyritic Nephelinite lavas and dykes of lower Jurassic Age, with a composition nearly equal to those found on the clay pits. That reveals the translation of strata from the Continental margin by large fluvial channels, that ended on the sea deposits of the Ciechocinek Formation Green series.
The Saubach Formation is a geological formation in Austria and Germany, dating to about 180–174 million years ago. It was described originally as Saubachschichten in 1975, and classified as part of the Lower Jurassic Adnet Group.
The Rya Formation is a geologic formation in Skåne County, southern Sweden. It is Early to early Middle Jurassic in age. The Rya Formation comprises siltstones, claystones, sandstones, mudstones and rare coal beds. The formation overlies the Höganäs Formation and is overlain by the Vilhelmsfält and Mariedal Formations.
Fulgoridiidae are an extinct family of Jurassic planthoppers. They are the earliest group of planthoppers known, and appear to be a paraphyletic assemblage ancestral to living planthoppers. All currently known species are from Eurasia.
The Djupadal Formation is a geologic formation in Skåne County, southern Sweden. It is Early Jurassic in age. It is part of the Central Skåne Volcanic Province, know by the discovery of basalt tuff layers, including Sandåkra, Korsaröd and Djupadal. An original analysis of the location of Korsaröd led to a Toarcian-Aalenian age, but was dismissed in 2016, when a series of Palynogical samples recovered a Late Pliensbachian and probably Lower Toarcian age for the Korsaröd Outcrop. The same year this result was also challenged by an in-depth study of the Lilla Hagstad neck that yield a Late Toarcian Age. The formation was deposited in the Central Skane region, linked to the late early Jurassic volcanism. The Korsaröd member includes a volcanic-derived Lagerstatten with exceptional fern finds. The data provided by fossilized wood rings showed that the location of Korsaröd hosted a middle-latitude Mediterranean-type biome in the late Early Jurassic, with low rainfall ratio, delayed to seasonal events. Superimposed on this climate were the effects of a local active Strombolian Volcanism and hydrothermal activity.
The Röddinge Formation is a geologic formation in Skåne County, southern Sweden. It is Early Jurassic (Sinemurian-Toarcian) in age. It is a unit with a limited degree of exposure, being identified mostly by its deposits on the Fyledalen Fault Zone, specially on Kurremölla, where is present the main fossil deposit. It is a unit known mostly for large museum collections and estimated to have a thickness of several hundreds of meters. It is also known for its large iron deposits. It is correlated with the mostly marine Rya Formation of western Skåne County, the Volcanic deposits of the Djupadal Formation and specially the Sorthat Formation of Bornholm.
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