The Early Cretaceous (geochronological name) or the Lower Cretaceous (chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma.
|Chronostratigraphic name||Lower Cretaceous|
|Geochronological name||Early Cretaceous|
|Regional usage||Global (ICS)|
|Time scale(s) used||ICS Time Scale|
|Time span formality||Formal|
|Lower boundary definition||Not formally defined|
|Lower boundary definition candidates|
|Lower boundary GSSP candidate section(s)||None|
|Upper boundary definition||FAD of the Planktonic Foraminifer Rotalipora globotruncanoides|
|Upper boundary GSSP||Mont Risoux, Hautes-Alpes, France|
|Upper GSSP ratified||2002|
Proposals for the exact age of the Barremian-Aptian boundary ranged from 126 to 117 Ma until recently (as of 2019), but based on drillholes in Svalbard the defining early Aptian Oceanic Anoxic Event 1a (OAE1a) was carbon isotope dated to 123.1±0.3 Ma, limiting the possible range for the boundary to c. 122–121 Ma. There is a possible link between this anoxic event and a series of Early Cretaceous large igneous provinces (LIP).
The Ontong Java-Manihiki-Hikurangi large igneous province, emplaced in the South Pacific at c. 120 Ma, is by far the largest LIP in Earth's history. The Ontong Java Plateau today covers an area of 1,860,000 km2. In the Indian Ocean another LIP began to form at c. 120 Ma, the Kerguelen Plateau–Broken Ridge, together covering 2,300,000 km2. Another LIP on the Liaodong Peninsula, China, c. 131–117 Ma, lasted for 10 million years. It was the result of the subduction of the Kula and Pacific plates, which was probably caused by a superplume.
The opening of the Central Atlantic continued as the Mid-Atlantic Ridge spread north to separate the Iberian Peninsula from the banks of Newfoundland and to connect to the Canada Basin in the Arctic Ocean. With the opening of the Labrador Sea, Greenland became a separate tectonic plate and Laurentia became North America. The Proto-Caribbean Sea continued to grow and the Paraná-Etendeka LIP began to break Africa into three pieces. The Falkland Plateau broke off from southern Africa at 132 Ma and Madagascar ceased to move independently c. 120 Ma. In the Panthalassic Ocean the Pacific Plate continued to grow; the Arctic Alaska-Chukotka terrane formed the Bering Strait. Continued rifting opened new basins in the Indian Ocean, separating India, Antarctica, and Australia.
By 110 Ma the Mid-Atlantic Ridge reached south into the Proto-Caribbean and South Atlantic, effectively separating South America from Africa, and continued rifting in the northern end completed the longitudinal extent of the Atlantic. In Panthalassa the Ontong-Java Mega-LIP resulted in the formation of new tectonic plates and in the Indian Ocean the Kerguelen LIP began to push India northward.
During this time many new types of dinosaur appeared or came into prominence, including ceratopsians, spinosaurids, carcharodontosaurids and coelurosaurs, while survivors from the Late Jurassic continued to persist.
Angiosperms (flowering plants) appeared for the first time during the Early Cretaceous; Archaefructaceae, one of the oldest fossil families (124.6 Ma) was found in the Yixian Formation, China.
Sinodelphys, a 125 Ma-old boreosphenidan mammal found in the Yixian Formation, China, is one of the oldest mammal fossils found. The fossil location indicates early mammals began to diversify from Asia during the Early Cretaceous. Sinodelphys was more closely related to metatherians (marsupials) than eutherians (placentals) and had feet adapted for climbing trees.Steropodon is the oldest monotreme (egg-lying mammal) discovered. It lived in Gondwana (now Australia) at 105 Ma.
See also Edit
- International Commission on Stratigraphy. "ICS - Chart/Time Scale". www.stratigraphy.org.
- Kennedy, W.; Gale, A.; Lees, J.; Caron, M. (March 2004). "The Global Boundary Stratotype Section and Point (GSSP) for the base of the Cenomanian Stage, Mont Risou, Hautes-Alpes, France" (PDF). Episodes. 27: 21–32. doi:10.18814/epiiugs/2004/v27i1/003. Retrieved 13 December 2020.
- Midtkandal et al. 2016, Abstract
- Taylor 2006, Abstract
- Coffin & Gahagan 1995, The Plateaux, p. 1047
- Wu et al. 2005, Abstract
- Renne et al. 1992, Abstract
- Seton et al. 2012, 140–120 Ma (Figs. 21 and 22)
- Seton et al. 2012, 120–100 Ma (Figs. 22 and 23)
- Herendeen, Patrick S.; Friis, Else Marie; Pedersen, Kaj Raunsgaard; Crane, Peter R. (2017-03-03). "Palaeobotanical redux: revisiting the age of the angiosperms". Nature Plants. 3 (3): 17015. doi:10.1038/nplants.2017.15. ISSN 2055-0278. PMID 28260783. S2CID 205458714.
- Sun et al. 2002, Abstract
- Lee et al. 2014
- Luo et al. 2003, Abstract
- Archer et al. 1985, Abstract
- Archer, M.; Flannery, T. F.; Ritchie, A.; Molnar, R. E. (1985). "First Mesozoic mammal from Australia—an early Cretaceous monotreme". Nature. 318 (6044): 363–366. Bibcode:1985Natur.318..363A. doi:10.1038/318363a0. S2CID 4342084. Retrieved 28 July 2019.
- Coffin, M. F.; Gahagan, L. M. (1995). "Ontong Java and Kerguelen Plateaux: Cretaceous Icelands?". Journal of the Geological Society. 152 (6): 1047–1052. Bibcode:1995JGSoc.152.1047C. CiteSeerX 10.1.1.884.6604. doi:10.1144/GSL.JGS.1995.152.01.27. S2CID 128821082.
- Lee, Michael S. Y.; Cau, A.; Naish, D.; Dyke, G. J. (2014). "Morphological Clocks in Paleontology, and a Mid-Cretaceous Origin of Crown Aves" (PDF). Systematic Biology. 63 (1): 442–449. doi:10.1093/sysbio/syt110. PMID 24449041. Retrieved 28 July 2019.
- Luo, Z. X.; Ji, Q.; Wible, J. R.; Yuan, C. X. (2003). "An Early Cretaceous tribosphenic mammal and metatherian evolution". Science. 302 (5652): 1934–1940. Bibcode:2003Sci...302.1934L. doi:10.1126/science.1090718. PMID 14671295. S2CID 18032860.
- Midtkandal, I.; Svensen, H. H.; Planke, S.; Corfu, F.; Polteau, S.; Torsvik, T. H.; Faleide, J. I.; Grundvåg, S.-A.; Selnes, H.; Kürschber, W.; Olaussen, S. (2016). "The Aptian (Early Cretaceous) oceanic anoxic event (OAE1a) in Svalbard, Barents Sea, and the absolute age of the Barremian-Aptian boundary". Palaeogeography, Palaeoclimatology, Palaeoecology. 463: 126–135. Bibcode:2016PPP...463..126M. doi:10.1016/j.palaeo.2016.09.023. S2CID 132576803.
- Renne, P. R.; Ernesto, M.; Pacca, I. G.; Coe, R. S.; Glen, J. M.; Prévot, M.; Perrin, M. (1992). "The age of Paraná flood volcanism, rifting of Gondwanaland, and the Jurassic-Cretaceous boundary". Science. 258 (5084): 975–979. Bibcode:1992Sci...258..975R. doi:10.1126/science.258.5084.975. PMID 17794593. S2CID 43246541.
- Seton, M.; Müller, R. D.; Zahirovic, S.; Gaina, C.; Torsvik, T.; Shephard, G.; Talsma, A.; Gurnis, M.; Maus, S.; Chandler, M. (2012). "Global continental and ocean basin reconstructions since 200Ma". Earth-Science Reviews. 113 (3): 212–270. Bibcode:2012ESRv..113..212S. doi:10.1016/j.earscirev.2012.03.002. Retrieved 23 October 2016.
- Sun, G.; Ji, Q.; Dilcher, D. L.; Zheng, S.; Nixon, K. C.; Wang, X. (2002). "Archaefructaceae, a new basal angiosperm family" (PDF). Science. 296 (5569): 899–904. Bibcode:2002Sci...296..899S. doi:10.1126/science.1069439. PMID 11988572. S2CID 1910388. Retrieved 28 July 2019.
- Taylor, B. (2006). "The single largest oceanic plateau: Ontong Java–Manihiki–Hikurangi" (PDF). Earth and Planetary Science Letters. 241 (3–4): 372–380. Bibcode:2006E&PSL.241..372T. doi:10.1016/j.epsl.2005.11.049. Retrieved 28 July 2019.
- Wu, F. Y.; Lin, J. Q.; Wilde, S. A.; Zhang, X. O.; Yang, J. H. (2005). "Nature and significance of the Early Cretaceous giant igneous event in eastern China". Earth and Planetary Science Letters. 233 (1–2): 103–119. Bibcode:2005E&PSL.233..103W. doi:10.1016/j.epsl.2005.02.019.