Map of the Oligocene (35 ma)
Copyright by Ron Blakey
During the Oligocene Australia and South America were completely separated from Antarctica. The Separation of South Amrica from Antarctica led to an Antarctic Circumpolar Current, which consequence is a cooling down of antarctica, followed by creation of an ice shield, resulting in a worldwide marine transgression.
India collided with Asia.
The cooling resulted in a fragmentation of biotic provinces and a reduced diversity of marin plancton, which is a starting point of the food chain.
The Oligocene is divided into the epochs:
L. Alegret, et al. 2008, p. 94:
- "The Oligocene in particular is considered a period marked by large and abrupt climate changes, paleogeographic changes including the opening of the Tasmanian Gateway and Drake Passage, large fluctuations in the volume of the Antarctic Ice Sheet after its initiation in the earliest Oligocene, with related eustatic changes at orbital frequencies (e.g., Wade and Pälike, 2004; Pälike et al., 2006). The formation of cold deep water in the Southern Ocean and/or in the northern Atlantic may have started in the earliest Oligocene (Kennett, 1977; Lawyer and Gahagan, 2003; Miller et al., 1991, 2005; Zachos et al., 2001), but the timing and pattern of these circulation changes is under vigorous debate (e.g., Barker and Thomas, 2004; Scher and Martin, 2004; Via and Thomas, 2006; Thomas and Via, 2007; Thomas et al., 2008). This transitional period in Earth's history was characterised by strong, short-term fluctuations between warmer and colder intervals that have been recognised and at least tentatively correlated around the world (Zachos et al., 2001). These climate fluctuations occur at orbital frequencies (Wade and Pälike, 2004; Coxall et al., 2005; Pälike et al., 2006), with some of the more extreme cold events (formerly called Oievents) occurring at low obliquity."
Garilli & Parrinello, 2014, p. 401-403:
- "The Late Eocene–Oligocene palaeogeographic reconstructions of those areas (Vincent 1990; Rögl 1999: figs. 2, 3; Rasser et al. 2008, with references) outline the North Sea and Paris Basins (N Atlantic realm) as distinct marine provinces separated by the Thule bridge, a wide land-passageway putting Great Britain in communication with central-western continental Europe until the Late Oligocene. At this time sporadic communications between the Atlantic and North Sea Basin occurred in the Channel area, as indicated by Janssen (1978b) on the basis of some Late Oligocene marine faunal affinities between the North Sea Basin and the Aquitaine Basin. However, it is possible that a southernmost connection favoured these interchanges as supposed by Rasser et al. (2008). The distribution of G. biangulata (Fig. 17) indicates that a faunal interchange (possibly unidirectional) between the North Sea and Paris Basins started in the Early Oligocene, when the Thule land-bridge was already in-filled (at least intermittently) in the Channel area, much earlier than had been supposed.
- [...] Notwithstanding this, Galeodinopsis seems never to have lived in the eastern part of the southern margin of the North Sea Basin, nor in the Paratethyan area, even though communication between the North Sea and Mediterranean/Paratethyan areas was established during that time, especially in the Early Oligocene, when ocean circulation supplied water from the North Sea to the Paratethys (Rögl 1999: figs. 1, 2). The distributional gap in the North Sea Basin may be at least partially explained by the paralic condition that affected the southeastern part of the North Sea Basin during Late Oligocene time (Rasser et al. 2008).
- [...] Tropical to warm-temperate conditions have been inferred for the Palaeogene of Europe (Vincent 1990) and, more specifically, subtropical conditions were indicated for the Late Oligocene of the North Sea Basin (Rasser et al. 2008). Actually, a warm (possibly tropical-subtropical) climatic regime in the Paleogene of the North Sea Basin is suggested by the analogies (at least at genus level) between the highly diverse molluscan assemblages from the Mediterranean Neogene and the Late Eocene–Oligocene of Germany, southwards to the Mainz basin: several molluscan taxa characteristic for warm climate, such as Bathytoma Harris and Burrows, 1891, Isognomon Lightfoot, 1786, Ficus Röding, 1798, Gemmula Weinkauff, 1875 and others, have been recorded in those areas (Janssen 1978b, 1979; Gründel 1997; Monegatti and Raffi 2001; Müller 2011). Furthermore, warm, tropical to subtropical, marine climatic conditions were inferred for this part of central Europe with particular regard to the Latdorfian faunal complex and similar assemblages of younger (Oligocene) age (Müller 2011). It is remarkable that from the middle Eocene onwards, the Cenozoic continental history of central Europe, in accordance with global marine oxygen isotope records, was characterized by the increasing degree of seasonality, and a short-term cooling at the base of the Aquitanian, approximating the Oligocene/Miocene boundary, was recorded in the Weisselster Basin, in central Germany (Mosbrugger et al. 2005). Also from a palaeogeographical point of view, the area of central-western Europe underwent remarkable changes. During the Early Miocene, marine regressive conditions rewrote the palaeogeography of the North Sea Basin, triggering the progressive reduction of its southernmost part, which was constrained to higher (presumably relatively colder) latitudes. Regressive conditions also caused the disappearance of satellite basins such as those in the Rhine Graben (e.g., the Mainz Basin; Rögl 1999). This palaeogeographic-climatic evolution was possibly responsible for the disappearance of Galeodinopsis from the mid-high latitudes of Central Europe and for its migration to the Iberian Atlantic coasts and into the (paleo)Mediterranean during Mio-Pliocene time. At the end of the Pliocene, at around 2.6 My B.P. (approximating the Piacenzian/Gelasian boundary), the marked onset of the continental ice sheet in the Northern Hemisphere (Shackleton et al. 1984) triggered stepwise climatic deteriorations at lower latitudes, causing the Mediterranean extinction of several molluscan taxa (Monegatti and Raffi 2001). The new climatic regime probably was the main cause of the disappearance of Galeodinopsis from the Mediterranean and its further migration towards the subtropical-tropical West Africa coasts, where this genus still lives. As for the ecological/bathymetrical requirements of Galeodinopsis, it is remarkable that for the Late Paleogene around Magderburg and Glimmerode (southern part of the North Sea Basin), where G. biangulata and G. semperi lived, the palaeofauna indicates normal marine conditions in rocky-sandy shore environments (Janssen 1978b; Mueller 2008, 2011). Also, the requirements of G. tiberiana are comparable, as indicated by its occurrence in the Pliocene sands of the Mediterranean Altavilla site, the depositional setting of which was mainly referred to infra-circalittoral shelf conditions (Dell’Angelo et al. 2012)."
- L. Alegret, L.E. Cruz, R. Fenero, E. Molina, S. Ortiz & E. Thomas, 2008. Effects of the Oligocene climatic events on the foraminiferal record from Fuente Caldera section (Spain, western Tethys); Palaeogeography, Palaeoclimatology, Palaeoecology 269 (2008): 94–102.
- Bosellini F. & Perrin C. 2008. Estimating Mediterranean Oligocene-Miocene sea-surface temperatures: An approach based on coral taxonomic richness. Palæogeography, Palæoclimatology, Palæoecology, Amsterdam, vol. 258, p. 71-88.
- Cadée, M.C. 1990. Het Oligoceen en de Oligocene Mollusken Fauna's van Nederland en omgeving; talk 10. Nov. 1990 in Amsterdam, Fulltext
- Cossmann M. (1892).- Révision sommaire de la faune du terrain oligocène marin aux environs d'Étampes.- Journal de Conchyliologie, Paris, t. 40, p. 330-375.
- Cossmann M. (1893).- Révision sommaire de la faune du terrain oligocène marin aux environs d'Étampes (suite).- Journal de Conchyliologie, Paris, t. 41, p. 297-363.
- Dockery D.T. III & Lozouet P. (2006).- Eocene-Oligocene molluscan extinctions and first appearance data across the North Atlantic in the North American Gulf Coastal Plain and Europe. In: Prothero D.R., Ivany L.C. & Nesbitt E.A. (eds.), From Greenhouse to Icehouse. The marine Eocene-Oligocene transition.- New York, Columbia University Press, p. 303-340.
- D. Esu, O. Girotti & J. Pignatti, 2005. Late Oligocene-?Miocene mollusc and foraminiferal assemblages from the vicinity of Otranto (Southern Apulia, Italy): a non-marine to marine transition; Rendiconti Soc. Paleont. Ital., 2(2005):75-85
- Garilli, V. and Parrinello, D. 2014. Taxonomy and palaeobiogeography of the Cenozoic Euro-Mediterranean rissoid gastropod Galeodinopsis and its relationship with close genera. Acta Palaeontologica Polonica 59 (2): 379–406, Fulltext
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- Harder, P. 1913. De oligocaene Lag i Jaernbanegennemskaeringen ved Arhus Station; Danmarks geologiske Undersoegelse (II) 22, pp. 1-140. Copenhagen
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- Harzhauser M., Piller W.E. & Steininger F.E. (2002).- Circum-Mediterranean Oligo-Miocene biogeographic evolution - the gastropods' point of view.- Palæogeography, Palæoclimatology, Palæoecology, Amsterdam, vol. 183, p. 103-133.
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- Janssen, A.W., 1989. Some new pteropod species from the North Sea Basin Cainozoic (Mollusca: Gastropoda, Euthecosomata). Mededelingen van de Werkgroep voor Tertiaire en Kwartaire Geologie 26 (3): 91-133
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