Journal articles on the topic 'Oligocene'
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1
Smith, R. "Insectivores (Mammalia) from the earliest Oligocene (MP 21) of Belgium." Netherlands Journal of Geosciences - Geologie en Mijnbouw 83, no. 3 (September 2004): 187–92. http://dx.doi.org/10.1017/s0016774600020254.
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AbstractInsectivore remains are not common in the Lower Oligocene of Europe. For this reason, the study of the earliest Oligocene insectivore fauna (MP 21) from Boutersem and Hoogbutsel, all together yielding nine species, representing five families, constitutes an important progress in the knowledge of the Late Eocene and Early Oligocene insectivore evolution. Some of the genera discovered in Belgium are known from upper Eocene sites (Saturninia, Amphidozotherium, Euronyctia, Eotalpa), whereas others are not known before the Oligocene (Butselia, Tetracus, Heterosoricinae ind.). The co-occurrence of primitive species of Nyctitheriidae with modern forms belonging to the Plesiosoricidae, Talpidae and Erinaceidae at the Eocene-Oligocene boundary suggests a transition fauna. Between the Priabonian (Late Eocene) and the Rupelian (Early Oligocene), the endemic European insectivores were in competition with the new immigrants. This faunal turnover is generally accepted as the ‘Grande Coupure’ event (the MP 21 event).
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Smith, R. "Insectivores (Mammalia) from the earliest Oligocene (MP 21) of Belgium." Netherlands Journal of Geosciences - Geologie en Mijnbouw 83, no. 3 (2004): 187–92. http://dx.doi.org/10.1017/s0016774600023489.
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AbstractInsectivore remains are not common in the Lower Oligocene of Europe. For this reason, the study of the earliest Oligocene insectivore fauna (MP 21) from Boutersem and Hoogbutsel, all together yielding nine species, representing five families, constitutes an important progress in the knowledge of the Late Eocene and Early Oligocene insectivore evolution. Some of the genera discovered in Belgium are known from upper Eocene sites (Saturninia, Amphidozotherium, Euronyctia, Eotalpa), whereas others are not known before the Oligocene (Butselia, Tetracus, Heterosoricinae ind.). The co-occurrence of primitive species of Nyctitheriidae with modern forms belonging to the Plesiosoricidae, Talpidae and Erinaceidae at the Eocene-Oligocene boundary suggests a transition fauna. Between the Priabonian (Late Eocene) and the Rupelian (Early Oligocene), the endemic European insectivores were in competition with the new immigrants. This faunal turnover is generally accepted as the ‘Grande Coupure’ event (the MP 21 event).
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Bui, Luan Thi. "PETROLEUM POTENTIAL OF SOURCE BEDS IN THE CUU LONG BASIN." Science and Technology Development Journal 14, no. 4 (December 30, 2011): 31–45. http://dx.doi.org/10.32508/stdj.v14i4.2025.
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In the Cuu Long basin, three source beds are identified: lower Miocene, Upper Oligocene, upper Eocene + lower Oligocene. They are separated from each other by sand-clay layers. Only Upper Oligocene and Upper Eocene + Lower Oligocene source beds are two main source beds supplying a great part of organic matter into traps. Petroleum source potential of Upper Oligocene source bed (66.30 billion tons) is greater than Upper Eocene + Lower Oligocene bed (29.88 billion tons). Total amount of hydrocarbon has ability to take part in accumulation process at the petroleumbearing traps from Upper Oligocene and Upper Eocene + Lower Oligocene source beds is over 2.19 billion tons and below 1.16 billion tons respectively. Thus, in whole CuuLong basin, source rocks have capacity to produce 96.18 billion tons of hydrocacbon in which accumulation is 3.35 billion tons making up 3.35% production quantity. Applying Monte - Carlo simulation method, using Crystal Ball software to calculate production potential and total amount of organic matter taking part into migration and accumulation process give rather appropriate result with difference level ≤ 1.25%.. Prospecting levels are in the following order: (i)Central lift zone has the greatest prospects, next is Dong Nai lift zone, graben located in north west inclined slope, south east inclined slope, north east area of Tam Dao lift zone finally. (2)Petroleum does not only accumulate in structural, combination traps but also in non-structural traps.
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Wade, Bridget S., and Heiko Pälike. "Oligocene climate dynamics." Paleoceanography 19, no. 4 (December 2004): n/a. http://dx.doi.org/10.1029/2004pa001042.
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Postgate, J., and F. G. Priest. "Putative oligocene spores." Microbiology 141, no. 11 (November 1, 1995): 2763–64. http://dx.doi.org/10.1099/13500872-141-11-2763.
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Tran, Huy Nhu, Xuan Van Tran, Kha Xuan Nguyen, Ngoc Ba Thai, Thanh Quoc Truong, Man Nguyen Tri Ho, Chuc Dinh Nguyen, and Lan Duc Tran. "Main favorable factorscreatee oligocene formation become a petroleum prospect in south-east area, Cuu Long basin." Science and Technology Development Journal 19, no. 1 (March 31, 2017): 169–79. http://dx.doi.org/10.32508/stdj.v19i1.515.
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The previous researchs almost demonstrated the reservoir in Lower Oligocene sandstone has complicated distribution, probably low porosity and permeability, no nature flow are seen by wells. Based on recent study results of depositional environment of E Oligocene sedimentary in Cuu Long basin and E sand distribution in blocks 01/10 & 02/10, block 09-2/09, block 09-2/10 and block 16-2 area, the paper determines depositional facies according to petrophysic and geophysic data. From Chrono-stratigraphy priciple, as well as interpretation and intergration of seismic data, well data, well log data, core & sample analysis results, petrophysic data, well test data, the paper forcuses on create correlation lines between wells and seismic line for confirming Oligocene E distribution in Cuu Long basin, buildup the gross mapping for depositional environment in sub-sequence Oligocene E upper and E lower and mapping of seismic attributes for sub-sequence Oligocene E upper and E lower.At last successfully predict the sand distribution in Oligocene E upper and E lower sub-sequence in research area and hence determine the stratigraphic traps in Oligocene formation of South-East area Cuulong basin.
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Prothero, Donald R. "North American mammalian diversity and Eocene–Oligocene extinctions." Paleobiology 11, no. 4 (1985): 389–405. http://dx.doi.org/10.1017/s0094837300011696.
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Diversity and faunal turnover of North American land mammals are calibrated against the magnetic polarity time scale for million-year intervals for the latest Eocene through late Oligocene. A major, gradual Late Eocene decline in diversity, caused mostly by an extended period of extinction of archaic forms, seems to be related to the worldwide crisis known as the “Terminal Eocene Event.” Along with other evidence of gradual changes in deep-sea microfossils, this evidence argues against a catastrophic explanation for late Eocene extinctions.Faunal stability characterized the rest of the Oligocene except for a wave of extinctions in the mid-Oligocene (Chadronian-Orellan boundary, about 32.4 ma). This mid-Oligocene event is sudden and severe, occurring in less than 200,000 yr, based on estimates from sedimentation rates calibrated from magnetic polarity interval boundaries. The mid-Oligocene event is found in many paleoclimatic records, but not in all of them. It may be related to the completion of the Circum-Antarctic Current and to increased mid-Oligocene glaciation.
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Gladenkov, Yu B. "The Oligocene of Sakhalin." Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 234, no. 1-3 (December 22, 2004): 433–40. http://dx.doi.org/10.1127/njgpa/234/2004/433.
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Tsai, Cheng-Hsiu, Toshiyuki Kimura, and Yoshikazu Hasegawa. "Coexistence of Oligocene toothed and baleen-assisted mysticetes in the northwestern Pacific." Fossil Record 27, no. 1 (January 11, 2024): 95–100. http://dx.doi.org/10.3897/fr.27.e111567.
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Oligocene mysticetes display an unparalleled diversity and morphological disparity in the evolutionary history of Mysticeti. However, their paleoecological aspects, such as the patterns of coexistence of different morphotypes, remain poorly explored. Here we describe an aetiocetid (toothed mysticete) from the Jinnobaru Formation (lower upper Oligocene, about 28 million years ago) of Umashima Island, Kitakyushu, Japan. Our description of a toothed mysticete from the Oligocene of Umashima exemplifies the coexistence of toothed and baleen-assisted mysticetes in the northwestern Pacific. Hopefully, new finds of Oligocene mysticetes will lead to a well-sampled dataset for analyzing this and other related paleoecological traits to understand the demise of “archaic” Oligocene mysticetes and the subsequent rise of the modern-looking baleen-bearing whales in Miocene times.
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Augé, Marc, and Daniel Pouit. "Presence of iguanid lizards in the European Oligocene Lazarus taxa and fossil abundance." Bulletin de la Société Géologique de France 183, no. 6 (December 1, 2012): 653–60. http://dx.doi.org/10.2113/gssgfbull.183.6.653.
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Abstract During the Eocene, iguanid lizards were a diverse and widespread group in Europe. Prior to this study, no iguanid was known in Europe after the Eocene-Oligocene boundary. Some specimens from the locality of Pech-du-Fraysse (late Oligocene, MP28, France, Phosphorites du Quercy) are described. They belong to the Iguanidae, more precisely to the genus Geiseltaliellus, demonstrating that iguanid lizards survived the Eocene-Oligocene extinctions in Europe, only to disappear in the aftermath, certainly during the latest Oligocene. Thus, Geiseltaliellus is recognized as a Lazarus taxa. Explanations pertaining to the Lazarus effect are examined.
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Lucas, Spencer G. "The first Oligocene mammal from New Mexico." Journal of Paleontology 60, no. 6 (November 1986): 1274–76. http://dx.doi.org/10.1017/s0022336000003000.
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Oligocene landscapes of New Mexico were dominated by andesite stratovolcanoes and resurgent domes of ash-flow tuff (ignimbrite) cauldrons (Smith et al., 1985). This pervasive volcanism produced volcanic and volcaniclastic rocks that have been neglected by vertebrate paleontologists, so that, until now, no Oligocene vertebrate fossils have been discovered in New Mexico. This documents the initial results of vertebrate paleontological investigations of Oligocene rocks in New Mexico, a lower jaw of the oromerycid artiodactyl Montanatylopus matthewi, the first Oligocene mammal from the state. In this paper, CM = Carnegie Museum of Natural History and UNM = University of New Mexico.
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Ayalew, Dereje. "Possible correlation of Oligocene climate changes with Ethiopian Oligocene ignimbrite eruptions." Arabian Journal of Geosciences 5, no. 5 (April 12, 2011): 999–1002. http://dx.doi.org/10.1007/s12517-011-0307-6.
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Moss, Graham D. "Foraminiferal turnover in neritic environments in the Oligocene of Southern Australia." Paleontological Society Special Publications 6 (1992): 217. http://dx.doi.org/10.1017/s2475262200007772.
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This study explores an excellent mid-latitude Oligocene calcareous neritic succession that spans the Eocene/Oligocene boundary to the Miocene. Rapid changes in sea level and climate should have a palpable influence on macroevolution and the Eocene-Oligocene transition marks one of the most substantial changes for the Cainozoic.Stratigraphic ranges of some 130 benthic and 20 planktic species occurring in two contrasting marine environments, one relatively restricted (low plankton - Murray Basin) and another more open (high plankton - Otway Basin) to oceanic processes, were identified and correlated with signals derived from changes in the physical environment. The signals include: the ‘Exxon’ sea-level curve, deep sea stable isotope curves, and prominent lithological changes.There is a significant turnover of species at the Eocene/Oligocene boundary. This event impacts on all assemblages and correlation metrics indicate that there is an ‘across-the-board’ response. Interestingly, the turnover corresponds to a local Saint Vincent Basin lithological change from the grey-green, organic rich facies of the Blanche Point Formation to the red-yellow-brown, well oxidized, quartz and bryozoa rich facies of the Port Willunga Formation. This switch is in turn coincident with the saltatory positive deviation in the δ18O top and bottom water curves derived from oceanic sections.The turnover pattern is not repeated at the major sea level fall predicted for the mid Oligocene (at 30 million years), neither is there any comparable lithological transition. Geographically widespread species (common to all environments) cross this supposed prominent type one sequence boundary, there is a signal but the impact on the fauna is less than that detected for the Eocene/Oligocene boundary. Those faunas that were more restricted to open ocean processes exhibited shorter stratigraphic ranges and appeared to be controlled primarily by sea level fluctuation and salinity changes. There is evidence to suggest that foraminiferal faunas of the more restricted environment in southern Australia were less responsive to the well mixed, thermohaline driven ocean of the Oligocene. Generally, Oligocene benthic assemblages are dominated by Cibicides, Notorotalia and Buliminid species in consistently high numbers, indicating a high dominance of relatively few taxa, that is, large populations and low diversity. Faunas of open ocean assemblages demonstrate relatively subdued turnover patterns compared to those of more restricted environments.The Late Eocene displays parallel patterns of foraminiferal turnover and the Oligocene is characterised by inter-basin contrasts. In comparison to the Eocene, faunas appear to be more robust in the psychrosphere constrained ocean of the Oligocene. It is proposed that these patterns indicate that the Latest Eocene was dominated by species adapted to a specialist life strategy while the Oligocene reflect patterns more often associated with opportunist colonization.
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Hoem, Frida S., Luis Valero, Dimitris Evangelinos, Carlota Escutia, Bella Duncan, Robert M. McKay, Henk Brinkhuis, Francesca Sangiorgi, and Peter K. Bijl. "Temperate Oligocene surface ocean conditions offshore of Cape Adare, Ross Sea, Antarctica." Climate of the Past 17, no. 4 (July 2, 2021): 1423–42. http://dx.doi.org/10.5194/cp-17-1423-2021.
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Abstract. Antarctic continental ice masses fluctuated considerably during the Oligocene “coolhouse”, at elevated atmospheric CO2 concentrations of ∼600–800 ppm. To assess the role of the ocean in the Oligocene ice sheet variability, reconstruction of past ocean conditions in the proximity of the Antarctic margin is needed. While relatively warm ocean conditions have been reconstructed for the Oligocene offshore of Wilkes Land, the geographical extent of that warmth is unknown. In this study, we reconstruct past surface ocean conditions from glaciomarine sediments recovered from Deep Sea Drilling Project (DSDP) Site 274 offshore of the Ross Sea continental margin. This site, located offshore of Cape Adare is ideally situated to characterise Oligocene regional surface ocean conditions, as it is situated between the colder, higher-latitude Ross Sea continental shelf and the warm-temperate Wilkes Land margin in the Oligocene. We first improve the age model of DSDP Site 274 using integrated bio- and magnetostratigraphy. Subsequently, we analyse organic walled dinoflagellate cyst assemblages and lipid biomarkers (TEX86, TetraEther indeX of 86 carbon atoms) to reconstruct surface palaeoceanographic conditions during the Oligocene (33.7–24.4 Ma). Both TEX86-based sea surface temperature (SST) and microplankton results show temperate (10–17 ∘C ± 5.2 ∘C) surface ocean conditions at Site 274 throughout the Oligocene. Oceanographic conditions between the offshore Wilkes Land margin and Cape Adare became increasingly similar towards the late Oligocene (26.5–24.4 Ma); this is inferred to be the consequence of the widening of the Tasmanian Gateway, which resulted in more interconnected ocean basins and frontal systems. Maintaining marine terminations of terrestrial ice sheets in a proto-Ross Sea with offshore SSTs that are as warm as those suggested by our data requires a strong ice flux fed by intensive precipitation in the Antarctic hinterland during colder orbital states but with extensive surface melt of terrestrial ice during warmer orbital states.
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Ochakovskyi, Volodymyr Yu. "CLIMATE RECONSTRUCTION OF SOUTHERN UKRAINE IN THE OLIGOCENE ON THE BASIS OF SPORE-POLLEN STUDY DATA BY THE COEXISTENCE APPROACH METHOD." Collection of Scientific Works of the Institute of Geological Sciences of the NAS of Ukraine 15, no. 1 (June 6, 2022): 112–22. http://dx.doi.org/10.30836/igs.2522-9753.2021.267861.
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Based on the data of spore-pollen studies of the Oligocene sediments of Southern Ukraine, a reconstruction of the Oligocene climate of this region was carried out using the latest method of coexistence approach. For each of the intervals of Oligocene time (early Borysphenian, late Borysphenian, Molochanian, Sirogozian, Askanian, and Hornostaivian) the values of the following climatic parameters were calculated: mean annual temperature, coldest month temperature (January), warmest month temperature (July), mean annual precipitation, highest month precipitation, lowest month precipitation, warmest month precipitation. It was established that the paleoclimate was warm, close to subtropical, with dry hot summers. It is classified as Csa type according to Köppen. A trend of gradual cooling and aridization of the climate within Southern Ukraine during the Oligocene was revealed. In the middle of the Oligocene (Molochanian — Sirogozian) an episode of noticeable warming and drying: an increase of continentality of the climate was recorded (an increase of mean annual temperature and a decrease of precipitation in the wettest month, a decrease of precipitation in the driest month and a decrease of precipitation in the warmest month), which corresponds to the period of the least development of the sea basin within the Southern Ukraine in the Oligocene.
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Lelono, Eko Budi, and Robert J. Morley. "Oligocene Climate Changes of Java." Scientific Contributions Oil and Gas 34, no. 3 (March 14, 2022): 169–76. http://dx.doi.org/10.29017/scog.34.3.803.
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The study of palynology performed on the Oligocene marine sediment of the East Java Sea provides excellent recovery which allows the construction of palynological succession which applies regionally (Lelono et. al., 2011). In fact, this succession is characterized by assemblages that suggest climatic changes. These assemblages are divided into two major groups including mangrove and hinterland. The hinterland pollen group shows the most interesting succession, with elements on the one hand suggesting everwet climates (Dacrydium and Casuarina), and seasonal elements on the other (Gramineae, Schoutenia and Malvacipollis diversus). Mangrove pollen however suggests strong environmental control since mangrove pollen shows different abundance variations in the two wells. The age of the studied succession is independently defined using combined marine micro-fossils of foraminifer and nannoplankton which indicate Early to Late Oligocene. Although for most of the Oligocene in Southeast Asia, seasonal climate assemblages are the rule, this study interpretes the appearence of everwet climates. The Early Oligocene is characterized by common rain forest elements, suggesting an everwet rain forest climate at that time. The early part of the Late Oligocene, however, contains much reduced rain forest elements, and the presence of regular Gramineae pollen, suggesting a more seasonal climate, whereas for the latest Late Oligocene, rain forest (and peat swamp) elements return in abundance, suggesting a very wet rain forest climate. In fact, Java region experienced the wettest climate during Oligocene which probably reflected a wet climate fringe to the eastern margin of Sundaland prior to the collision of the Australian and Asian plates at the Oligo-Miocene boundary.
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Lelono, Eko Budi. "POLLEN RECORDS FROM THE OLIGOCENE OF WESTERN INDONESIA AS THE EVIDENCES OF CLIMATE CHANGES." Scientific Contributions Oil and Gas 40, no. 3 (September 24, 2018): 107–15. http://dx.doi.org/10.29017/scog.40.3.46.
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In Southeast Asia, Oligocene climate is well known to be represented by dry/ seasonal climate. However, it was reported possible appearance of wet climate period during the expantion of dry condition. This work is aimed to confi rm the Oligocene climate which occurred in western Indonesia. Climate change is useful to understand the Oligocene stratigraphy of Western Indonesia. This study uses cutting samples from off shore exploration wells situated in West and East Java and West Natuna as well as on-shore Central Sumatera and West Java. Samples are processed using standard preparation methods to produce suitable pollen assemblage for quantitative analysis.This study proves that the Oligocene sediments yield rich pollen assemblages including those of environment and climate indicators. Abundant fresh water algae of Pediastrum and Bosedinia in Early Oligocene indicates the appearance of lacustrine sediments. This sediment was formed under dry/ seasonal climate as marked by rich grass pollen Monoporites annulatus in the absence or rare occurance of rain forest elements. Mean while, Late Oligocene is characterised by common brackish elements to indicate shifting paleoenvironment into transition to shallow marine. The climate was changing into wetter condition as evidenced by high appearance of Dacrydium and Casuarina as well as other rain forest palynomorphs. The wettest climate probably occured in Java region which refl ected a wet climate fringe to the eastern margin of Sundaland prior to the collision of the Australian and Asian Plates at the Oligo-Miocene boundary. However, in general, dry/ seasonal climate is the rule for most of the Oligocene in Western Indonesia.
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SELIM, S. S. "Sedimentological architecture, shelf-edge trajectories and evolution of an Oligocene reservoir, East Nile Delta." Geological Magazine 155, no. 3 (August 5, 2016): 747–71. http://dx.doi.org/10.1017/s0016756816000522.
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Abstract3D seismic data and wireline logs from 17 wells in the onshore East Nile Delta were utilized to study the stratigraphic architecture and evolution of Oligocene deposits. The Oligocene is readily recognized on seismic cross-sections by a series of northward prograding clinoforms. The Oligocene sequences show lateral facies changes from fluvial to deepwater via a shelf-edge delta. Such deltaic features include distributary channels, interdistributary bay fill, and a delta plain and front, gradually changing downslope into prodelta and slope deposits. The slope deposits include three main depositional elements: a deeply incised channel, a complex of laterally switched leveed channels and lobes, and crevasses and frontal splays. These depositional elements are formed in the main western slope basin and local eastern intraslope ponded sub-basin. The reactivated E–W- and NW-trending faults as well as NE–SW inverted structures are the main controls on slope physiography that formed the main corridors for Oligocene sediment distribution. Two main globally correlated Oligocene sequences are encountered being separated by the major drop in global eustatic sea level at 28.1Ma. The lower Oligocene sequence has two main stages: (1) the formation and filling of a basal canyon; and (2) the formation and progradation of shelf deltas to form shelf-edge deltas, and then progradation with an ascending shelf-edge trajectory (clinoforms 1). The upper Oligocene sequence is characterized by accretionary shelf-edge deltas with descending and then flat trajectories (clinoforms 2–4). The frontal splay and lobe complex exhibits potentially favourable reservoir continuity and areal coverage followed by the slope channels.
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Hably, Lilla, and Boglárka Erdei. "The Late Oligocene flora of Hungary." Acta Palaeobotanica 63, no. 2 (December 31, 2023): 162–227. http://dx.doi.org/10.35535/acpa-2023-0011.
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In Hungary, late Oligocene (Chattian, reg. str. Kiscellian and Egerian) plant remains have been preserved in sediments of the Törökbálint (Mány and Kovačov members) and Eger formations. An overview and revision of these late Oligocene macrofloras, both newly excavated and already published, are presented. Nearly a hundred plant taxa are described from the localities Andornaktálya, Csörög, Eger Wind-brickyard, Kesztölc, Környe, Leányfalu, Máriahalom, Nagysáp, Pomáz, Pusztaberki, Rétság, Tarján, Verőcemaros, and Vértesszőlős. Floristic results help understand and interpret the flora and vegetation change during the Oligocene. The appearance of temperate floristic elements in the late Oligocene floras may have been related to habitats strongly influenced by edaphic factors and the better adaptability of the new, temperate elements to a quickly changing environment.
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Van Simaeys, S. "The Rupelian-Chattian boundary in the North Sea Basin and its calibration to the international time-scale." Netherlands Journal of Geosciences - Geologie en Mijnbouw 83, no. 3 (September 2004): 241–48. http://dx.doi.org/10.1017/s0016774600020308.
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AbstractThe classical problem of the nature and age of the Rupelian-Chattian (Early-Late Oligocene) unconformity in its type region is here approached using organic walled dinoflagellate cyst (dinocyst) correlations between the North Sea Basin and well-calibrated central Italian (Tethyan Ocean) sections. Useful Oligocene dinocyst events are the last occurrence ofEnneadocysta pectiniformis(~29.3 Ma), and the first occurrences ofSaturnodinium pansum(~29.4 Ma),Distatodinium biffii(~27.9 Ma) andArtemisiocysta cladodichotoma(~26.7 Ma).The latter event marks the earliest Chattian. The improved correlations indicate that the Rupelian-Chattian (R-C) boundary is associated with the so-called ‘Oligocene Glacial Maximum’. This phase of important global cooling and glacio-eustatic sea level fall is genetically related to the unconformity between the classic Oligocene stages. Subsequent global warming (so-called ‘Late Oligocene Warming Event’), induced a major sea level rise, leading e.g. to the time-transgressive deposition of the typical basal Chattian glauconitic sands. The oldest of the Chattian units have a GPTS age of-26.7 Ma. It further appears that a hiatus of ~500 kyrs spans the classic Rupelian-Chattian unconformity.
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Van Simaeys, S. "The Rupelian-Chattian boundary in the North Sea Basin and its calibration to the international time-scale." Netherlands Journal of Geosciences - Geologie en Mijnbouw 83, no. 3 (2004): 241–48. http://dx.doi.org/10.1017/s0016774600023532.
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AbstractThe classical problem of the nature and age of the Rupelian-Chattian (Early-Late Oligocene) unconformity in its type region is here approached using organic walled dinoflagellate cyst (dinocyst) correlations between the North Sea Basin and well-calibrated central Italian (Tethyan Ocean) sections. Useful Oligocene dinocyst events are the last occurrence ofEnneadocysta pectiniformis(~29.3 Ma), and the first occurrences ofSaturnodinium pansum(~29.4 Ma),Distatodinium biffii(~27.9 Ma) andArtemisiocysta cladodichotoma(~26.7 Ma). The latter event marks the earliest Chattian. The improved correlations indicate that the Rupelian-Chattian (R-C) boundary is associated with the so-called ‘Oligocene Glacial Maximum’. This phase of important global cooling and glacio-eustatic sea level fall is genetically related to the unconformity between the classic Oligocene stages. Subsequent global warming (so-called ‘Late Oligocene Warming Event’), induced a major sea level rise, leading e.g. to the time-transgressive deposition of the typical basal Chattian glauconitic sands. The oldest of the Chattian units have a GPTS age of ~26.7 Ma. It further appears that a hiatus of ~500 kyrs spans the classic Rupelian-Chattian unconformity.
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Oszczypko-Clowes, Marta, and Bartłomiej Żydek. "Paleoecology of the Upper Eocene-Lower Oligocene Malcov Basin based on the calcareous nannofossils: a case study of the Leluchów section (Krynica Zone, Magura Nappe, Polish Outer Carpathians)." Geologica Carpathica 63, no. 2 (April 1, 2012): 149–64. http://dx.doi.org/10.2478/v10096-012-0012-8.
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Paleoecology of the Upper Eocene-Lower Oligocene Malcov Basin based on the calcareous nannofossils: a case study of the Leluchów section (Krynica Zone, Magura Nappe, Polish Outer Carpathians)During the period of ca. 20 Ma (Middle Eocene-Chattian) the Leluchów Succession of the Magura Basin passed through drastic changes of sedimentary condition and paleobathymetry from well oxygened red shales withReticulofragmium amplectens, deposited beneath CCD, redGlobigerinaoozes, to oxygen depleted organic-rich menilite-type shales and finally to flysch deposition of open marine conditions. The biostratigraphic and lithostratigraphic scheme is well established with the Leluchów Marl Member — Zones NP19-20 to NP22 (Late Eocene-Early Oligocene), Smereczek Shale Member, Zone NP23 (Early Oligocene) and the Malcov Formation s.s., Zone NP24 (Early-Late Oligocene). The aim of the paper is to present the quantitative analyses as the basis for paleoecological changes in the Magura Basin during the Late Eocene-Late Oligocene period. The changes manifest themselves through a decrease in the water temperature and progressing eutrophication. Species typical of brackish water conditions and restricted to the Paratethys region were identified from the NP23 Zone.
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Wolfe, J. A. "The eocene-oligocene transition." Earth-Science Reviews 38, no. 1 (March 1995): 89–91. http://dx.doi.org/10.1016/0012-8252(95)90061-6.
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Pashko, Pandeli. "Morave Mt Oligocene-Middle Miocene succession of Albanian-Thessalian Basin." Bulletin of the Geological Society of Greece 52, no. 1 (September 28, 2018): 1. http://dx.doi.org/10.12681/bgsg.15837.
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The Morava Mountain Oligocene-Middle Miocene molasse deposits take part in the Albanian-Thessalian Basin, which developed NW-SE from eastern Albania to Thessaly in Greece, where it is called as Mesohellenic Basin. The 4.5 km thick basin infill is subdivided into three molasse cycles separated by two regional unconformities at the Eocene/Oligocene and Aquitanian/Burdigalian boundaries. The Morava Mountain Oligocene-Middle Miocene molase, ~ 3500 m thick, represents an exposed continuous, rich in fossil fauna succession. Six stratigraphic sections were studied and measured.
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NEL, ANDRÉ, and CRISTIAN PELLA. "A new genus and species of spoon-winged lacewing from the Cretaceous Crato Formation in Brazil (Neuroptera: Nemopteridae)." Palaeoentomology 3, no. 4 (August 31, 2020): 338–41. http://dx.doi.org/10.11646/palaeoentomology.3.4.2.
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The lacewing family Nemopteridae Burmeister, 1839 is very poorly represented in the fossil record with three Early Cretaceous genera of uncertain affinities from the Brazilian Crato Formation, one ‘mid’-Cretaceous representative of the stem group of the Crocinae Navás, 1910 in the Burmese amber, and two Cenozoic nemopterine genera Marquettia Navás, 1913 (late Eocene-early Oligocene) and Paleonemia Claisse et al., 2019 (middle Oligocene). Also two undetermined Nemopterinae are recorded from the late Eocene and the Oligocene (Lu et al., 2019a: Table 1; Claisse et al., 2019).
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Wessels, Wilma, Andrew A. van de Weerd, Hans de Bruijn, and Zoran Marković. "Dipodidae (Mammalia, Rodentia) from the Paleogene of south-east Serbia." Palaeobiodiversity and Palaeoenvironments 100, no. 3 (October 28, 2019): 841–48. http://dx.doi.org/10.1007/s12549-019-00392-5.
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Abstract Isolated cheek teeth of the Asian dipodid Heosminthus primiveris from four early Oligocene localities in the Koritnica-Babušnica basin, south-east Serbia, are described. The record of the Paleogene Dipodidae of Central Asia and Europe is briefly discussed. The current view of the migration pattern of the Paleogene Dipodidae between central Asia and Europe is revised: the migration of Plesiosminthus into Europe during the late Oligocene was preceded by the immigration of Heosminthus into the Serbo-Macedonian high (S. E. Europe) during the early Oligocene.
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Novoselov, K. A. "Geoturism in Africa. the Simien Mountains." МИНЕРАЛОГИЯ (MINERALOGY) 7 (April 2021): 90–94. http://dx.doi.org/10.35597/2313-545x-2021-7-1-7.
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The paper is dedicated to the geological structure of Ethiopia and Simien Mountains, which are located in the northern part of the North Ethiopian Plateau composed of Oligocene plateau basalts hosting Oligocene-Miocene shield volcanoes.
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Karwowska, Ewa, Ewa Miaśkiewicz-Pęska, Katarzyna Gołębiewska, and Paulina Tomaszewska. "Microbiological Hazards Associated with the Use of Oligocene Waters: A Study of Water Intakes in Warsaw, Poland." Microorganisms 11, no. 4 (March 24, 2023): 826. http://dx.doi.org/10.3390/microorganisms11040826.
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Oligocene waters are widely recognized as excellent sources of drinking water. Due to the belief in their good quality, the water from Oligocene intakes in Warsaw, Poland, is made available to users without prior treatment or disinfection. The present study aimed at assessing possible microbiological risks associated with the use of this water. The occurrence of microbiological contaminants in selected intakes was evaluated, in addition to an assessment of possible changes in the microbiological quality of the water under typical storage conditions. The possibility of antibiotic resistance in bacteria isolated from Oligocene water samples was also investigated, as was their sensitivity to selected disinfectants. A small number of bacteria—27.0 ± 60.8 CFU/cm3 and 3.0 ± 3.0 CFU/cm3—were found in Oligocene water intakes for psychrophilic and mesophilic bacteria, respectively. Fecal bacteria were not detected. Bacteria present in Oligocene waters showed the ability to multiply intensively during standard water storage; this was especially true for mesophilic bacteria in water stored at room temperature. In some samples, bacterial counts reached 103–104 CFU/cm3 after 48 h. Almost all bacterial isolates were resistant to the commonly used antibiotics: ampicillin, vancomycin and rifampicin. The bacteria were also insensitive to some disinfectants.
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CHEN, YUNFA, WILLIAM OKI WONG, QIAN HU, YONGQING LIUFU, and ZHIMING XIE. "A new fossil-species of Acer (Sapindaceae) from the Ningming Basin in Guangxi, South China." Phytotaxa 298, no. 2 (March 10, 2017): 158. http://dx.doi.org/10.11646/phytotaxa.298.2.5.
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Acer ningmingensis Y.F.Chen & W.O.Wong sp.nov. is described for asymmetric samaras from the Oligocene Ningming Formation in Guangxi Zhuang Autonomous Region, South China. It represents the Oligocene Acer occurrence in the lowest latitude and the only record from a tropical zone today. Together with the coeval fossil record from the mid-latitudes in China, Korea and Japan, the present discovery suggests that the genus Acer had been widely distributed in East Asia by the Oligocene, during which the climate in the Ningming area was cooler than the present.
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Bitner, Maria, and Andreas Kroh. "First record of the genus Bronnothyris (Brachiopoda: Megathyrididae) from the Oligocene of the Mainz Basin (Germany)." Geologica Carpathica 62, no. 3 (June 1, 2011): 203–9. http://dx.doi.org/10.2478/v10096-011-0017-8.
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First record of the genusBronnothyris(Brachiopoda: Megathyrididae) from the Oligocene of the Mainz Basin (Germany)The genusBronnothyris, with the type speciesTerebratula bronniiRoemer, 1841, was erected for thoseArgyrothecaspecies that have septal flanges extended ventrally from the dorsal valve. Four other Late Cretaceous and one Early Paleocene species were attributed to this genus (i.e.Argyrotheca coniunctaSteinich, 1965,A. lacunosaSteinich, 1965,A. obstinataSteinich, 1965,A. stevensisNielsen, 1928 andA. rugicostaZelinskaya, 1975). After examination of Oligocene material from Waldböckelheim, Mainz Basin, Germany we transfer the speciesArgiope subradiataSandberger, 1862 into the genusBronnothyris. This new combination extends the stratigraphic range ofBronnothyrisinto the Oligocene.
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SELL, I., G. POUPEAU, J. M. GONZÁLEZ-CASADO, and J. LÓPEZ-MARTÍNEZ. "A fission track thermochronological study of King George and Livingston islands, South Shetland Islands (West Antarctica)." Antarctic Science 16, no. 2 (June 2004): 191–97. http://dx.doi.org/10.1017/s0954102004001907.
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This paper reports the dating of apatite fission tracks in eleven rock samples from the South Shetland Archipelago, an island arc located to the north-west of the Antarctic Peninsula. Apatites from Livingston Island were dated as belonging to the Oligocene (25.8 Ma: metasediments, Miers Bluff Formation, Hurd Peninsula) through to the Miocene (18.8 Ma: tonalites, Barnard Point). Those from King George Island were slightly older, belonging to the Early Oligocene (32.5 Ma: granodiorites, Barton Peninsula). Towards the back-arc basin (Bransfield Basin), the apatite appears to be younger. This allows an opening rate of approximately 1.1 km Ma−1 (during the Miocene–Oligocene interval) to be calculated for Bransfield Basin. Optimization of the apatite data suggests cooling to 100 ± 10°C was coeval with the end of the main magmatic event in the South Shetland Arc (Oligocene), and indicates slightly different tectonic-exhumation histories for the different tectonic blocks.
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Fraass, Andrew J., and R. Mark Leckie. "Oligocene Planktic Foraminiferal Taxonomy and Evolution: An Illustrated Revision of Ocean Drilling Program Site 803." Journal of Foraminiferal Research 51, no. 3 (July 31, 2021): 139–64. http://dx.doi.org/10.2113/gsjfr.51.3.139.
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ABSTRACT The Oligocene (33.9–23.0 Ma) has historically proven to be a difficult interval to examine with respect to planktic foraminifera; the tendency for many of the taxa to be basically globigerine in shape, with 4 or 5 chambers in the final whorl means differences between species are limited. Recently, an international working group has attempted to clarify the Oligocene planktic foraminiferal taxonomy, with the goal of establishing phylogenetically-consistent generic and species concepts. A relatively expanded and continuous Oligocene section recovered at Ocean Drilling Program Site 803 in the western equatorial Pacific was previously studied by Leckie et al. (1993) using fairly conservative species concepts. Since 1993, foraminiferal biostratigraphic datum age calibrations have changed, and so revised sedimentation rates for the 220-m thick Oligocene sequence are actually more constant than previously thought. As a part of the recent taxonomic revision, this site was reevaluated and numerous additional taxa are recorded at this location. Macroevolutionary rates are calculated from the occurrences, and increased extinction is found within the late Oligocene, counter to the expectations laid out in broader-scale macroevolutionary studies. An effort is made here to describe the diagnostic features, which can be used to distinguish all taxa under a standard binocular microscope. Finally, several figures of scanning electron microscope photomicrographs (from Site 803 and tropical Atlantic Ocean ODP Site 628) depict features used to describe and differentiate important, but difficult or homeomorphic taxa, with the hope that these figures can be used by other workers at the microscope attempting to do Oligocene taxonomy-based studies.
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Nguyen, Anh Lam, Tung Thanh Nguyen, Long Van Hoang, Dung Viet Bui, Hieu Trung Nguyen, Anh Tuan Nguyen, Phuong Ngoc Thi Bui, Trieu Tan Nguyen, and Trung Thanh Trinh. "Variation of sediment provenance at the 09 - 1 Block, Cuu Long Basin: their significance in assessing the Oligocene - Miocene reservoir quality." Journal of Mining and Earth Sciences 62, no. 5 (October 31, 2021): 29–42. http://dx.doi.org/10.46326/jmes.2021.62(5).03.
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The Cuu Long Basin is one of the Tertiary sedimentary basins situated on the continental shelf of Vietnam, which demonstrates the high potential of oil and gas. Apart from fractured granite reservoirs, the Oligocene - Miocene sand bodies are thought to have significant potential for forming non - structural traps. The results of the study on the composition and physical properties of the sediments derived from wells "X" and "Y", block 09 - 1, Cuu Long Basin show that there is a clear difference between the Late Oligocene and Early Miocene sandstone in the well "X", namely the Miocene sandstone shows larger particle size, higher roundness and sortness (TB: 434.2; Ro: 0.69; So: 2.22) than those of the Late Oligocene sandstone (TB: 104.28; Ro: 0.64; So: 1.46). This difference is likely attributed to the fact that the Miocene sandstone was influenced by the marine environment, which intensified the roundness and sortness. Meanwhile, the well "Y" did not show much difference in the physical parameters of the sediments between the Late Oligocene and Early Miocene age ranges. However, the grain size was slightly increased and the roundness was less during the Early Miocene. It is possible that the “Y” well is located closer to the local source. The variation in the physical parameters of the sediments, proportion of sand grains and clay minerals shows that the quality of late Oligocene reservoir is better than that of Early Miocene reservoir, and the Late Oligocene reservoir quality in the "X" well is better than that in the borehole "Y".
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OKAY, ARAL I., ERCAN ÖZCAN, AYNUR HAKYEMEZ, MUZAFFER SIYAKO, GÜRSEL SUNAL, and ANDREW R. C. KYLANDER-CLARK. "The Thrace Basin and the Black Sea: the Eocene–Oligocene marine connection." Geological Magazine 156, no. 1 (September 18, 2017): 39–61. http://dx.doi.org/10.1017/s0016756817000772.
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AbstractThe Late Cretaceous – Recent West Black Sea Basin and the Eocene–Oligocene Thrace Basin are separated by the Strandja arch comprising metamorphic and magmatic rocks. Since Late Cretaceous time the Strandja arch formed a palaeo-high separating the two basins which accumulated clastic sediment of >9 km thickness. During late Eocene – early Oligocene time the marine connection between these basins existed through the Çatalca gap west of Istanbul. The Çatalca gap lies on the damage zone of a major Cretaceous strike-slip fault; it formed a 15 km wide marine gateway, where carbonate-rich sediments of thicknessc.350 m were deposited. The sequence consists of upper Eocene shallow marine limestones (SBZ18-20) overlain by upper Eocene – lower Oligocene (P16-P19 zones) pelagic marl with a rich fauna of planktonic foraminifera; the marls are intercalated with 31–32 Ma acidic tuff and calc-arenite beds. The Çatalca gap is bounded in the west by a major normal fault, which marks the eastern boundary of the Thrace Basin. Seismic reflection profiles, well data and zircon U–Pb ages indicate that the Thrace Basin sequence west of the fault is late Eocene – middle Oligocene (37–27 Ma) in age and that the fault has accommodated 2 km of subsidence. Although there was a marine connection between the West Black Sea and Thrace basins during late Eocene – early Oligocene time, no significant exchange of clastic sediment took place. Sedimentation in the Çatalca gap ended abruptly during early Oligocene time by uplift, and this eventually led to the paralic conditions in the Thrace Basin.
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Kiel, Steffen, and Kazutaka Amano. "The earliest bathymodiolin mussels: an evaluation of Eocene and Oligocene taxa from deep-sea methane seep deposits in western Washington State, USA." Journal of Paleontology 87, no. 4 (July 2013): 589–602. http://dx.doi.org/10.1666/12-135.
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Bathymodiolin mussels are a group of bivalves associated with deep-sea hydrothermal vents and other reducing deep-sea habitats, and they have a particularly rich early Cenozoic fossil record in western Washington State, U.S.A. Here we recognize six species from middle Eocene to latest Oligocene deep-water methane seep deposits in western Washington. Two of them are new: Vulcanidas? goederti from the middle Eocene Humptulips Formation and Bathymodiolus (sensu lato) satsopensis from the late Oligocene part of the Lincoln Creek Formation. Very similar to the latter but more elongate are specimens from the early Oligocene Jansen Creek Member of the Makah Formation and are identified as B. (s.l.) aff. satsopensis. Bathymodiolus (s.l.) inouei Amano and Jenkins, 2011 is reported from the Lincoln Creek Formation. Idas? olympicus Kiel and Goedert, 2007 was previously known from late Eocene to Oligocene whale and wood falls in western Washington and is here reported from Oligocene seep deposits of the Makah and Pysht Formations. Vulcanidas? goederti occurs at a seep deposit from a paleodepth possibly as great as 2000 m, suggesting that its living relative, Vulcanidas insolatus Cosel and Marshall, 2010, which lives at depths of only 150–500 m, is derived from a deep-water ancestor. The bathymodiolins in western Washington indicate that the group originated at least in the middle Eocene and underwent a first diversification in the late Eocene to Oligocene. Early ontogenetic shells of all fossil species investigated so far, including the middle Eocene Vulcanidas? goederti, reflect planktotrophic larval development indicating that this developmental mode is an ancestral trait of bathymodiolins.
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Ladant, J. B., Y. Donnadieu, and C. Dumas. "Links between CO<sub>2</sub>, glaciation and water flow: reconciling the Cenozoic history of the Antarctic Circumpolar Current." Climate of the Past Discussions 10, no. 3 (May 22, 2014): 2397–416. http://dx.doi.org/10.5194/cpd-10-2397-2014.
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Abstract. The timing of the onset of the Antarctic Circumpolar Current (ACC) is a crucial event of the Cenozoic because of its cooling and isolating effect over Antarctica. It is intimately related to the glaciations occurring throughout the Cenozoic from the Eocene–Oligocene (EO) transition (≈34 Ma) to the middle Miocene glaciations (≈13.9 Ma). However, the exact timing of the onset remains debated with evidence for a late Eocene set up contradicting others data pointing to an occurrence closer to the Oligocene–Miocene (OM) boundary. In this study, we show the potential impact of the Antarctic ice sheet on the initiation of a proto-ACC at the EO boundary. Our results reveal that the regional cooling effect of the ice sheet increases the sea ice formation, which disrupts the meridional density gradient in the Southern Ocean and leads to the onset of a circumpolar current and its progressive strengthening. We also suggest that subsequent variations in atmospheric CO2, ice sheet volumes and tectonic reorganizations may have affected the ACC intensity after the Eocene–Oligocene transition, which in turn may provide an explanation for the second initiation of the ACC at the Oligocene–Miocene boundary and may reconcile evidence supporting both early Oligocene and early Miocene onset of the ACC.
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O’Brien, Charlotte L., Matthew Huber, Ellen Thomas, Mark Pagani, James R. Super, Leanne E. Elder, and Pincelli M. Hull. "The enigma of Oligocene climate and global surface temperature evolution." Proceedings of the National Academy of Sciences 117, no. 41 (September 28, 2020): 25302–9. http://dx.doi.org/10.1073/pnas.2003914117.
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Falling atmospheric CO2levels led to cooling through the Eocene and the expansion of Antarctic ice sheets close to their modern size near the beginning of the Oligocene, a period of poorly documented climate. Here, we present a record of climate evolution across the entire Oligocene (33.9 to 23.0 Ma) based on TEX86sea surface temperature (SST) estimates from southwestern Atlantic Deep Sea Drilling Project Site 516 (paleolatitude ∼36°S) and western equatorial Atlantic Ocean Drilling Project Site 929 (paleolatitude ∼0°), combined with a compilation of existing SST records and climate modeling. In this relatively low CO2Oligocene world (∼300 to 700 ppm), warm climates similar to those of the late Eocene continued with only brief interruptions, while the Antarctic ice sheet waxed and waned. SSTs are spatially heterogenous, but generally support late Oligocene warming coincident with declining atmospheric CO2. This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO2and/or ocean gateways, and is only partially explained by current climate models. Although the dominant climate drivers of this enigmatic Oligocene world remain unclear, our results help fill a gap in understanding past Cenozoic climates and the way long-term climate sensitivity responded to varying background climate states.
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NGÔ-MULLER, VALERIE, KILLYAN BLOT, and ANDRÉ NEL. "A new species of Nothochrysa from the latest Oligocene of France (Insecta: Neuroptera: Chrysopidae)." Palaeoentomology 2, no. 2 (April 5, 2019): 111–14. http://dx.doi.org/10.11646/palaeoentomology.2.2.2.
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The green lacewings or Chrysopoidea are relatively rare in the fossil record, especially for the Cenozoic, while they seem to be rather diverse and frequent in the Mesozoic (Nel et al, 2005; Makarkin & Menon, 2005). The Chrysopidae seem to be better represented in the Eocene and the Miocene than in the Oligocene outcrops (e.g. Makarkin, 1991; Makarkin & Archibald, 2013). The Oligocene record for these insects is currently reduced to two species, both in the genus Nothochrysa McLachlan, 1868. Here we describe a new Oligocene green lacewing from the lacustrine Konservat-Lagerstätte of Aix-en-Provence.
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Bannikov, A. F., and I. G. Erebakan. "A new species of horse mackerel fish of the genus <i>Archaeus</i> (Carangidae, Percomorpha) from the Lower Oligocene of the North Caucasus." Палеонтологический журнал, no. 2 (March 1, 2023): 80–87. http://dx.doi.org/10.31857/s0031031x23020046.
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A new species of horse mackerel fish (Carangidae), Archaeus solus sp. nov., was described based on the imprint of a complete skeleton from the Lower Oligocene (Pshekha Formation) of Gorny Luch locality. This is the third known species of the Eocene–Oligocene genus Archaeus Agassiz, 1844, and the first discovery of Carangidae in the Oligocene of the North Caucasus. The new species differs from A. glarisianus Agassiz, 1844 from the Rupelian of Switzerland and A. oblongus Daniltshenko, 1968 from the basal Eocene of Turkmenistan by a larger number of rays in both the spiny and soft dorsal fin.
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Ingemann Schnetler, Kai, Henrik Madsen, Kasia K. Śliwińska, Claus Heilmann-Clausen, and Kaare Ulleberg. "A late Oligocene molluscan fauna and Oligocene coastal outcrops from Vilsund, NW Denmark." Bulletin of the Geological Society of Denmark 73 (February 9, 2024): 1–40. http://dx.doi.org/10.37570/bgsd-2024-73-01.
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Abstract: A rich late Oligocene molluscan fauna from a coastal cliff at Vilsund on the island of Mors, Jylland, Denmark, was studied. A summary of the upper Palaeogene sedimentary sequence in NW Jylland is given and lithostratigraphical and biostratigraphical correlations are suggested. The molluscan fauna contains 120 species, and the nonmolluscs are briefly mentioned. The new species Mitromorpha (Mitrolumna) danica n. sp. and Cerithiopsis vilsundensis n. sp. are established. Mitromorpha (Mitrolumna) danica n. sp. is the first representative of the gastropod genus Mitromorpha Carpenter, 1865 and subgenus Mitrolumna Bucquoy, Dautzenberg & Dollfus, 1883 from the Cenozoic of Denmark. Eubela (s. lat.) zetes (Kautsky, 1925) represents the oldest record of the genus Eubela Dall, 1889. Andersondrillia Schnetler & Beyer, 1990 is considered to be a junior synonym of Benthomangelia Thiele, 1925. The bivalve genus Cubiostrea Sacco, 1897 is recorded from the upper Oligocene of the North Sea Basin for the first time. In the systematical part, several species are treated, including 16 species which have not been recorded previously from the Danish upper Oligocene; a synopsis of the representatives of the genus Streptodictyon Tembrock, 1961 in the Danish Oligocene is also given. Aphanitoma ingerae Schnetler & Palm, 2008 is transferred to the genus Mitromorpha, subgenus Mitrolumna. The fauna is compared with other Danish and German late Oligocene faunas and palaeoecological interpretations are suggested. As many of the mollusc species have not previously been illustrated from the Dan– ish upper Oligocene, the fauna is extensively illustrated. Dinocyst assemblages have been studied to help date the investigated successions. The assemblages indicate that the glauconitic clay from Vilsund should be assigned to the provisionally named stratigraphical Unit X in Śliwińskaet al. (2012) or the lowermost Brejning Formation. Unit X was previously only known from the interval 61.5–67.5 m in the Harre-1 borehole. Schnetler & Beyer (1990) assigned the glauconitic clay in the coastal cliff at Mogenstrup to the Brejning Formation, but dinocyst studies herein indicate that these strata should be assigned either to Unit X, most likely the upper part, or the lowermost Brejning Formation (see Appendix). This interpretation is supported by the foraminifers and the pectinid species Palliolum hausmanni (Goldfuss, 1835). The occurrence of other nearby outcrops of differing Oligocene ages is demonstrated. The outcrops are described and dated by means of dinocysts and foraminifers and include a section showing a depositional contact between the lowermost Rupelian Viborg Formation and Chattian Branden Clay. The age of the Mogenstrup section is also demonstrated by means of dinocysts.
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Clausen, Ole Rønø. "Tectonic vs climatic control on the sequence development, examples from the Paleogene succession in the eastern North Sea area." Bulletin of the Geological Society of Denmark 45 (September 25, 1998): 63–71. http://dx.doi.org/10.37570/bgsd-1998-45-07.
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A sequence stratigraphic subdivision of the upper Paleocene and the Oligocene is used to exemplify the influence of regional tectonism, local tectonism and climatic changes onto sedimentation in an epicontinental basin. The analysis shows that the low sedimentation rate and the condensed character of the Paleocene sediments disable any identification of climatic changes, whereas the Oligocene sequence boundaries are controlled by glacio-eustatic sea level changes. Regional tectonism played a major role in generating areas exposed for erosion located east of the present North Sea Basin. These exposed areas generated sand rich mass flows during the late Paleocene and generated the large amount of sediments which prograded into the Norwegian-Danish Basin during the Oligocene Local tectonics controlled generation of topographic depressions in the western part of the Norwegian-Danish Basin. The subtle depressions controlled the location of the sand rich mass flow deposits both during the late Paleocene and the latest Oligocene.
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Abdelghany, Osman, and Mahmoud Faris. "Early Oligocene calcareous nannofossils, planktonic and larger foraminifera from the United Arab Emirates, Oman Mountains." Micropaleontology 63, no. 6 (2018): 445–56. http://dx.doi.org/10.47894/mpal.63.6.06.
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The Lower Oligocene Asmari Formation occupies the western and eastern flanks of the Jabal Hafit anticline and the western limb of the Jabal Malaqet-Mundassah anticline in the southeast of the United Arab Emirates near the Oman border. In this area the Asmari Formation unconformably overlies the Upper Eocene Dammam Formation. In this study an Early Oligocene characteristic assemblage of calcareous nannofossils, foraminifera, corals, calcareous algae, bryozoa, mollusks and echinoids is described from the carbonate rocks of the Asmari Formation. The Asmari stratigraphic succession is dated by analysis of the calcareous nannofossil assemblages and planktonic and larger foraminifera. The results of this study indicate that the succession falls within the Early Oligocene Zones NP24 and P20-P21. About seventeen nannofossil species are documented for the first time in this formation, along with three planktonic and larger foraminiferal species. The Oligocene rocks in the study area provide results consistent with a shallow-water inner shelf within the photic zone.
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Antoine, Pierre-Olivier, Stéphane Ducrocq, Laurent Marivaux, Yaowalak Chaimanee, Jean-Yves Crochet, Jean-Jacques Jaeger, and Jean-Loup Welcomme. "Early rhinocerotids (Mammalia: Perissodactyla) from South Asia and a review of the Holarctic Paleogene rhinocerotid record." Canadian Journal of Earth Sciences 40, no. 3 (March 1, 2003): 365–74. http://dx.doi.org/10.1139/e02-101.
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The earliest rhinocerotids from South Asia are identified on the basis of few dental remains originating from the Late Eocene of Thailand (Wai Lek mine, Krabi Basin) and the Early Oligocene of Pakistan (Paali nala C2, Bugti Hills). Once synthesized, the Holarctic Paleogene rhinocerotid record points out a westward diachronism of rhinocerotid First Appearance Data, from North America to Europe via Asia, throughout mid-Cenozoic times. The faunal similarity among mammal localities from the Late Eocene and Early Oligocene of peninsular Thailand, southern China, and Pakistan suggests the existence of a single South Asian paleoprovince during this interval and the persistence of a tropicalsubtropical climate. Substantial faunal changes recorded in eastern Balochistan reveal a significant climatic deterioration from the middle part of the Oligocene. Neither provinciality nor endemism is noticeable for rhinocerotoid taxa recognized in the Oligocene of the Indian subcontinent: neither the Himalayas nor the Tibet Plateau was a paleogeographic barrier for large mammals during this interval.
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WELCOMME, JEAN-LOUP, MOULOUD BENAMMI, JEAN-YVES CROCHET, LAURENT MARIVAUX, GRÉGOIRE MÉTAIS, PIERRE-OLIVIER ANTOINE, and IBRAHIM BALOCH. "Himalayan Forelands: palaeontological evidence for Oligocene detrital deposits in the Bugti Hills (Balochistan, Pakistan)." Geological Magazine 138, no. 4 (July 2001): 397–405. http://dx.doi.org/10.1017/s0016756801005428.
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In the southwestern Sulaiman geological province (Balochistan, Pakistan), terrestrial detrital facies from the Bugti Hills region have yielded the richest Tertiary vertebrate faunas to be found in Asia thus far. New fossils from five successive and distinct ‘bone beds’ bridge the supposed Oligocene sedimentary hiatus within the Sulaiman geological province; the lowermost continental levels of the previously described Miocene Chitarwata Formation, known as the Bugti Member, are Oligocene in age in the Bugti area. Neither a mixture of heterochronic faunal elements nor endemism of any fauna is evident in this area. Additional microfaunal material from the Bugti Member constrains an Oligocene age for the lower Chitarwata Formation in Zinda Pir (northeast of the Bugti Hills). This Oligocene transition between the marine Kirthar (Eocene) and continental Siwalik (Miocene) deposits consists of a regressive fluvio-deltaic system occupying a vast floodplain. It represents an early-stage molasse in the palaeo-Indus Basin which drained western orogenic highlands resulting from the collision between the Indian and Eurasian plates.
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Prothero, Donald R., Elizabeth Draus, and Casey Burns. "Magnetostratigraphy and Tectonic Rotation of the Eocene-Oligocene Makah and Hoko River Formations, Northwest Washington, USA." International Journal of Geophysics 2009 (2009): 1–15. http://dx.doi.org/10.1155/2009/930612.
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The Eocene-Oligocene Makah Formation and subjacent middle Eocene Hoko River Formation of the northwestern Olympic Peninsula, Washington, yield mollusks, crustaceans, foraminifera, and early neocete whales; their age has never been precisely established. We sampled several sections; most samples showed a stable single-component remanence held largely in magnetite and passed a Class I reversal test. The upper Refugian (late Eocene) and lower Zemorrian (early Oligocene) rocks at Baada Point correlate with Chron C13r (33.7–34.7 Ma) and Chron C12r (30–33 Ma). The Ozette Highway section of the Makah Formation spanned the early Refugian to late Refugian, with a sequence that correlates with Chrons C15r-C13r (33.7–35.3 Ma), and a long reversed early Zemorrian section that correlates with Chron C12r (30–33 Ma). The type section of the Hoko River Formation correlates with Chron C18r (40.0–41.2 Ma). The area sampled shows about45∘of post-Oligocene counterclockwise tectonic rotation, consistent with results obtained from the Eocene-Oligocene rocks in the region.
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Podobina, V. M. "NEW DATA ON BIOSTRATIGRAPHY OF THE TAVDA HORIZON (RYUPELIAN STAGE) IN WESTERN SIBERIA (BASED ON THE RESULTS OF THE STUDY OF FORAMINIFERA)." Geology and mineral resources of Siberia, no. 4 (December 2022): 3–13. http://dx.doi.org/10.20403/2078-0575-2022-4-3-13.
Full textAbstract:
The problematic point in the Paleogene biostratigraphy of Western Siberia is the age of the Tavda Horizon as well as the position of Oligocene Stages. In the regional stratigraphic chart for the Paleogene of Western Siberia, unicellular algae and some other data were used as the basis for conclusions on the age of the Tavda Formation (Horizon). As a result, the age of the Tavda Horizon is dated back to the Late Bartonian (Middle Eocene). According to the foraminifera data using geological information, as well as publiсations, the age of the Tavda Horizon is defined as the Ryupelian (Middle Oligocene). The Latdorfian Stage of the Lower Oligocene, as it turned out, falls out of the stratigraphic section of Western Siberia due to manifestation of positive tectonic movements, the rise of this and other northern regions. In the southern regions of Europe, the USA, and the Atlantic, the Latdorfian Stage is present as the Lower Oligocene or as planktonic foraminiferous zones.
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Archer, M., R. Arena, M. Bassarova, K. Black, J. Brammall, B. Cooke, P. Creaser, et al. "The Evolutionary History and Diversity of Australian Mammals." Australian Mammalogy 21, no. 1 (1999): 1. http://dx.doi.org/10.1071/am99001.
Full textAbstract:
Palaeodiversity and relationships of all groups of Australian mammals are reviewed. The fossil record spanning this time is of variable quality. 'Dark Ages' about which nothing is known in terms of Australian mammal evolution include the late Triassic to late Jurassic, late Cretaceous to late Paleocene and middle Eocene to middle Oligocene. Very little is known about the early Cretaceous and late Miocene. The late Oligocene to middle Miocene record documents the highest levels of biodiversity known for the continent, comparable to that which characterises the lowland rainforests of Borneo and Brazil. Order Monotremata spans at least the last 110 million years and includes four families. The enigmatic Ausktribosphenos from 115 million-year-old sediments in Victoria may represent an archaic monotreme, specialised peramurid or previously undocumented order of mammals but is unlikely to represent a placental as suggested in the initial description. Order Microbiotheria is represented in the early Eocene (~55 mya) by two genera similar in morphology to early Eocene taxa from Argentina. Order Peramelemorphia spans the early Eocene to Holocene and includes at least five families. Order Dasyuromorphia spans at least the late Oligocene to Holocene and includes at least three families. Other dasyuromorphian-like marsupials are indeterminate in terms of family-level affinities. Order Notoryctemorphia spans the early Miocene to Holocene with one family. Order Yalkaparidontia spans the late Oligocene to middle Miocene with one genus. Order Diprotodontia spans the late Oligocene to Holocene, represented throughout by three major groups: Phalangerida (eight families), Vombatomorphia (seven families) and Macropodoidea (at least three families). A possible placental condylarth (Tingamarra) has been recorded from the early Eocene. An archaeonycteridid bat (Australonycteris) is known from the early Eocene. Among bats, the late Oligocene to middle Miocene is dominated by rhinolophoids, many of which have European, Asian and African affinities. Mystacinids, megadermatids, hipposiderids and molossids are well-represented in the Oligocene to Miocene deposits. Vespertilionids are uncommon in the Oligocene to Miocene but become more diverse in the Pliocene to Holocene. Emballonurids and rhinolophids appear for the first time in the Plio-Pleistocene. Pteropodids are unknown prior to the Holocene. Murids span the early Pliocene to Holocene. In the oldest assemblage at Riversleigh, one undescribed lineage resembles archaic forms otherwise only known from the fossil records of Africa and Eurasia.
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Lekkas, E., G. Danamos, and E. Skourtsos. "IMPLICATIONS FOR THE CORRELATION OF THE HELLENIC NAPPES IN SW AEGEAN: THE GEOLOGICAL STRUCTURE OF THE ARCHANGELOS REGION, RHODES ISLAND." Bulletin of the Geological Society of Greece 40, no. 1 (June 8, 2018): 374. http://dx.doi.org/10.12681/bgsg.16622.
Full textAbstract:
In the region of Archangelos in central-eastern Rhodes, a nappe sequence from bottom to top consists of i) Laerma unit, an Oligocene age wildflysch, ii) Archangelos unit, a neritic limestone of Upper Triassic - Mid Eocene age grading through red pelites to a flysch sequence, probably combarable to Ethia unit of Crete, iv) the Profus Ilias unit, a pelagic sequence ofplaty limestones and radiolarites of Upper Triassic - Upper Cretaceous age, similar to Pindos Unit and v) the ophiolites. The emplacement of the nappes on the relative autochthonous Laerma unit was carried out in surface conditions and is due to gravitational sliding estimated during Lower Oligocene to Middle - Upper Oligocene.
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De Man, E., and S. Van Simaeys. "Late Oligocene Warming Event in the southern North Sea Basin: benthic foraminifera as paleotemperature proxies." Netherlands Journal of Geosciences - Geologie en Mijnbouw 83, no. 3 (September 2004): 227–39. http://dx.doi.org/10.1017/s0016774600020291.
Full textAbstract:
AbstractThe investigation of foraminiferal assemblages from a series of Oligocene borehole sections allowed paleoenvironment and paleoclimate reconstructions for the Rupelian and Chattian (Lower and Upper Oligocene) Stages in their type region, the southern North Sea Basin. A striking feature coinciding with the Rupelian-Chattian (R-C) unconformity is the major change in paleotemperature and paleobathymetry. The shallow marine to restricted marine subtropical fauna at the base of the Chattian is in strong contrast with the deeper marine and cooler upper Rupelian assemblages. This study suggests that the early Chattian transgression is genetically related to a widespread major warming pulse, known as the Late Oligocene Warming Event.
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De Man, E., and S. Van Simaeys. "Late Oligocene Warming Event in the southern North Sea Basin: benthic foraminifera as paleotemperature proxies." Netherlands Journal of Geosciences - Geologie en Mijnbouw 83, no. 3 (2004): 227–39. http://dx.doi.org/10.1017/s0016774600023520.
Full textAbstract:
AbstractThe investigation of foraminiferal assemblages from a series of Oligocene borehole sections allowed paleoenvironment and paleoclimate reconstructions for the Rupelian and Chattian (Lower and Upper Oligocene) Stages in their type region, the southern North Sea Basin. A striking feature coinciding with the Rupelian-Chattian (R-C) unconformity is the major change in paleotemperature and paleobathymetry. The shallow marine to restricted marine subtropical fauna at the base of the Chattian is in strong contrast with the deeper marine and cooler upper Rupelian assemblages. This study suggests that the early Chattian transgression is genetically related to a widespread major warming pulse, known as the Late Oligocene Warming Event.