The Aptian is an age in the geologic timescale or a stage in the stratigraphic column . It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately. The Aptian succeeds the Barremian and precedes the Albian , all part of the Lower/Early Cretaceous.
7-526: The Wallumbilla Formation is an Aptian geologic formation found in Australia. Plesiosaur and theropod remains are among the fossils that have been recovered from its strata. The formation is present in the Northern Territory, Queensland, South Australia, and New South Wales. It is a sedimentary unit, principally made up of mudstone and siltstone, with calcareous concretions. Its maximum thickness
14-755: Is 600 metres. Its age is somewhere from Aptian to Albian , that is between 125 and 101 Mya. The formation is part of the Wilgunya Subgroup, which in turn is part of the Rolling Downs Group of the Eromanga and Surat Basins . The named beds are the Coreena, Doncaster, Jones Valley, Ranmoor, and Trimble Members. Aptian The Aptian partly overlaps the upper part of the Western European Urgonian Stage. The Selli Event, also known as OAE1a,
21-556: Is also known for its crystallized fruits. The original type locality is in the vicinity of Apt. The Aptian was introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1840. The base of the Aptian Stage is laid at magnetic anomaly M0r. A global reference profile for the base (a GSSP ) had in 2009 not yet been appointed. The top of the Aptian (the base of the Albian)
28-494: Is at the first appearance of coccolithophore species Praediscosphaera columnata in the stratigraphic record. In the Tethys domain , the Aptian contains eight ammonite biozones : Sometimes the Aptian is subdivided in three substages or subages: Bedoulian (early or lower), Gargasian (middle) and Clansayesian (late or upper). In modern formal chronostratigraphy the Aptian is divided into Lower and Upper sub-stages. The Lower Aptian
35-829: Is equivalent to the Bedoulian, and it includes the oglanensis to furcata Tethyan ammonite zones. The Upper Aptian is equivalent to the Gargasian and Clansayesian, it includes the subnodosocostatum to jacobi Tethyan ammonite zones (Gradstein et al. 2004). Examples of rock units formed during the Aptian are: Antlers Formation , Cedar Mountain Formation , Cloverly Formation , Elrhaz Formation , Jiufotang Formation , Little Atherfield , Mazong Shan , Potomac Formation , Santana Formation , Twin Mountains Formation , Xinminbao Group and Yixian Formation . A cold episode occurred at
42-447: The start of the Aptian, as evidenced by the migration of the dinoflagellates Cepadinium variabilis and Pseudoceratium nohrhansenii into lower latitudes. A decline in global p CO 2 occurred from about 1,000 ppm to 800 ppm from the start of the Aptian to the C10 positive carbon isotope excursion. During the late Aptian, p CO 2 was between 515 ± 79 and 1029.8 ± 158 ppm as evidenced by
49-547: Was one of two oceanic anoxic events in the Cretaceous Period, which occurred around 120 Ma and lasted approximately 1 to 1.3 million years, being marked by enhanced silicate weathering , as well as ocean acidification . The Aptian extinction was a minor extinction event hypothesized to have occurred around 116 to 117 Ma. The Aptian was named after the small city of Apt in the Provence region of France , which
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