Piacenzian

The Piacenzian is in the international geologic time scale the upper stage or latest age of the Pliocene. It spans the time between 3.6 ± 0.005 Ma and 2.588 ± 0.005 Ma (million years ago). The Piacenzian is after the Zanclean and is followed by the Gelasian (part of the Pleistocene).

Piacenzian
Chronology
Formerly part ofTertiary Period/System
Etymology
Name formalityFormal
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definitionBase of Gauss/Gilbert (C2An/C2Ar) magnetic reversal
Lower boundary GSSPPunta Piccola Section, Porto Empedocle, Sicily, Italy
37.2889°N 13.4933°E / 37.2889; 13.4933
Lower GSSP ratifiedJanuary 1997[4]
Upper boundary definition
Upper boundary GSSPMonte San Nicola Section, Gela, Sicily, Italy
37.1469°N 14.2035°E / 37.1469; 14.2035
Upper GSSP ratified1996 (as base of Gelasian)[5]

The Piacenzian is roughly coeval with the European land mammal age MN 16, overlaps the late Chapadmalalan and early Uquian South American land mammal age and falls inside the more extensive Blancan North American land mammal age. It also correlates with the Astian, Redonian, Reuverian and Romanian regional stages of Europe, and the Waipipian and Mangapanian stages of New Zealand. Some authorities describe the British Red Crag Formation and Waltonian Stage as late Piacenzian,[6][7] while others regard them as early Pleistocene.[8][9]

Carbon dioxide levels during the Piacenzian were similar to those of today, making this age, with global mean temperature 2–3 °C higher and sea levels about twenty meters higher than today, an important analogue for predictions of the future of our world.[10]

Definition

The Piacenzian was introduced in scientific literature by Swiss stratigrapher Karl Mayer-Eymar in 1858. It is named after the Italian city of Piacenza.

The base of the Piacenzian is at the base of magnetic chronozone C2An (the base of the Gauss chronozone and at the extinction of the planktonic forams Globorotalia margaritae and Pulleniatina primalis. The GSSP for the Piacenzian Stage is at Punta Piccola on Sicily, Italy.[11]

The top of the Piacenzian (the base of the Quaternary System and the Pleistocene Series) is defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone (at the Gauss-Matuyama reversal), and isotopic stage 103. Above this point there are notable extinctions of the calcareous nannofossils: Discoaster pentaradiatus and Discoaster surculus.[12]

Climate

The Piacenzian was the last age before the Quaternary glaciations started to take hold in the Northern hemisphere. The ice sheet of Antarctica was also less prominent than today and sea levels were approximately twenty meters higher than the present. The global mean temperature was 2–3 °C warmer than the pre-industrial temperature. During the Mid-Piacenzian Warm Period the concentration of carbon dioxide peaked at approximately 389 ppm (in the range 381–427 ppm with 95% confidence), thus similar to the concentration during the 2010s. The Piacenzian can therefore be used as an analogue to the future climate and sea level to expect if the carbon dioxide concentration stabilizes at this level. In particular, the KM5c interglacial during the Mid-Piacenzian Warm Period occurred during an orbital configuration close to the current situation, with similar geographical distribution of solar insolation.[10]

Climate of the Piacenzian would have started as a somewhat wet and warm period in North America occurring just after a brief cooling period of the Zanclean. Deposition of sediments and mollusks of the Piacenzian correspond with the rise in sea level creating the Tamiami Subsea and Jackson Subsea of Florida, Duplin Subsea generally of South Carolina, and Yorktown Subsea of the Outer Banks and inland North Carolina. Dates have been established on the basis of the genera and species of mollusks found.[13]

Origin of the genus Homo

The late Piacenzian may be when the genus Homo developed out of the ancestral genus Australopithecus.[14] While the oldest known fossils unambiguously identified as Homo habilis date to just after the end of the Piacenzian (2.58 Ma), a fossilized jawbone that exhibits traits that are transitional between Australopithecus and Homo habilis was discovered in the Afar Triangle in 2015. The find was made by Ethiopian student Chalachew Seyoum at a site called Ledi-Geraru between the Mille and Awash rivers, in Afar Regional State (near 11.36°N 40.86°E / 11.36; 40.86).[15][16] Based on geological evidence from the Afar region, the individual would have lived just after a major climate shift, during which forests and waterways were rapidly replaced by arid savanna. Regarding the Afar region, and as stated in the journal Science: "Vertebrate fossils record a faunal turnover indicative of more open and probable arid habitats than those reconstructed earlier in this region, in broad agreement with hypotheses addressing the role of environmental forcing in hominin evolution at this time." This interpretation is consistent with hypotheses that emphasize the savanna as the ancestral environment that shaped the evolution of early Homo and other hominins.[17]

References
Wikimedia Commons has media related to Piacenzian.

Notes
  1. Krijgsman, W.; Garcés, M.; Langereis, C. G.; Daams, R.; Van Dam, J.; Van Der Meulen, A. J.; Agustí, J.; Cabrera, L. (1996). "A new chronology for the middle to late Miocene continental record in Spain". Earth and Planetary Science Letters. 142 (3–4): 367–380. Bibcode:1996E&PSL.142..367K. doi:10.1016/0012-821X(96)00109-4.
  2. Retallack, G. J. (1997). "Neogene Expansion of the North American Prairie". PALAIOS. 12 (4): 380–390. doi:10.2307/3515337. JSTOR 3515337. Retrieved 2008-02-11.
  3. "ICS Timescale Chart" (PDF). www.stratigraphy.org.
  4. Castradori, D.; D. Rio; F. J. Hilgen; L. J. Lourens (1998). "The Global Standard Stratotype-section and Point (GSSP) of the Piacenzian Stage (Middle Pliocene)" (PDF). Episodes. 21 (2): 88–93. doi:10.18814/epiiugs/1998/v21i2/003. Retrieved 26 December 2020.
  5. Rio, Domenico; R. Sprovieri; D. Castradori; E. Di Stefano (1998). "The Gelasian Stage (Upper Pliocene): A new unit of the global standard chronostratigraphic scale". Episodes. 21 (2): 82–87. doi:10.18814/epiiugs/1998/v21i2/002.
  6. "Red Crag Formation". British Geological Survey. Retrieved 5 August 2016.
  7. "Global Chronostratigraphical Correlation Table for the Last 2.7 Million Years. v.2011". University of Cambridge. Retrieved 5 August 2016.
  8. "The Naze citation" (PDF). Sites of Special Scientific Interest. Natural England. Archived from the original (PDF) on 4 March 2016. Retrieved 5 August 2016.
  9. Allaby, Michael (2013). Oxford Dictionary of Geology & Earth Sciences (4th ed.). Oxford University Press. p. 626. ISBN 978-0-19-96530 6-5.
  10. de la Vega, E.; Chalk, T. B.; Wilson, P. A.; Bysani, R. P.; Foster, G. L. (2020). "Atmospheric CO2 during the Mid-Piacenzian Warm Period and the M2 glaciation". Scientific Reports. 10 (1): 11002. Bibcode:2020NatSR..1011002D. doi:10.1038/s41598-020-67154-8. PMC 7347535. PMID 32647351.
  11. Castradori et al. (1998)
  12. Gadstein et al. (2005), p. 28; Rio et al. (1998)
  13. Petuch, Edward J., Ph.D. Florida Atlantic University, Department of Geodsciences. Cenozoic Seas: The View From Eastern North America. CRC Press, Dec. 29, 2003. ISBN 0-8493-1632-4.
  14. Pallab Ghosh (4 March 2015). "'First human' discovered in Ethiopia". BBC. Retrieved 22 March 2015.
  15. "Oldest known member of human family found in Ethiopia". New Scientist. 4 March 2015. Retrieved 7 March 2015.
  16. Ghosh, Pallab (4 March 2015). "'First human' discovered in Ethiopia". bbc.co.uk. Retrieved 7 March 2015.
  17. Erin N. DiMaggio EN; Campisano CJ; Rowan J; Dupont-Nivet G; Deino AL; et al. (2015). "Late Pliocene fossiliferous sedimentary record and the environmental context of early Homo from Afar, Ethiopia". Science. 347 (6228): 1355–9. Bibcode:2015Sci...347.1355D. doi:10.1126/science.aaa1415. PMID 25739409.

Literature
Wikisource has original works on the topic: Cenozoic#Neogene
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