Modeling Eocene Asian climate with geologically revised paleogeography

Rhinoceroses have been considered to have originated from tapiroids in the middle Eocene; however, the transition remains controversial, and the first unequivocal rhinocerotoids appeared about 4 Ma later than the earliest tapiroids of the Early Eocene. Here we describe 5 genera and 6 new species of rhinoceroses recently discovered from the early Eocene to the early middle Eocene deposits of the Erlian Basin of Inner Mongolia, China. These new materials represent the earliest members of rhinocerotoids, forstercooperiids, and/or hyrachyids, and bridge the evolutionary gap between the early Eocene ceratomorphs and middle Eocene rhinocerotoids. The phylogenetic analyses using parsimony and Bayesian inference methods support their affinities with rhinocerotoids, and also illuminate the phylogenetic relationships and biogeography of Ceratomorpha, although some discrepancies are present between the two criteria. The nearly contemporary occurrence of various rhinocerotoids indicates that the divergence of different rhinocerotoid groups occurred no later than the late early Eocene, which is soon after the split between the rhinocerotoids and the tapiroids in the early early Eocene. However, the Bayesian tip-dating estimate suggests that the divergence of different ceratomorph groups occurred in the middle Paleocene.

Palaeoenvironmental periodisms of middle Eocene terrestrial sediments in Bohai Bay Basin, eastern China, and their implications for organic matter accumulation

Research Article| February 01, 1971 Age and Correlation of the Eocene Ulatisian and Narizian Stages, California P. LEWIS STEINECK; P. LEWIS STEINECK Department of Geology, Louisiana State University, Baton Rouge, Louisiana 70803 Search for other works by this author on: GSW Google Scholar JAMES M GIBSON JAMES M GIBSON Department of Geological Sciences, University of Southern California, Los Angeles, California 90007 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1971) 82 (2): 477–480. https://doi.org/10.1130/0016-7606(1971)82[477:AACOTE]2.0.CO;2 Article history received: 11 Sep 1970 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation P. LEWIS STEINECK, JAMES M GIBSON; Age and Correlation of the Eocene Ulatisian and Narizian Stages, California. GSA Bulletin 1971;; 82 (2): 477–480. doi: https://doi.org/10.1130/0016-7606(1971)82[477:AACOTE]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Paleogene strata crop out along the western boundary of the San Joaquin Basin, in the Santa Barbara Embayment, and in the San Diego Basin, California. Eocene strata are represented by the Ulatisian and Narizian benthic foraminiferal stages (middle and late Eocene, respectively) of Mallory (1959). These provincial stages are used currently for both age assignment and interbasin correlation. Planktonic foraminifers in the Rose Canyon Shale, Poway Conglomerate, and the Matilija, Cozy Dell, Lodo, and Sacate Formations suggest that these formations, as a whole, range in age from late early Eocene to late middle Eocene. Previous authors assigned various elements of the aforementioned formations either to the Ulatisian or Narizian stages. Planktonic foraminiferid species suggest that the Ulatisian stage ranges in age from late early Eocene to early middle Eocene, and the Narizian stage ranges in age from early middle Eocene to late middle Eocene. The time-transgressive nature of ecologically controlled benthic foraminifers is apparent. Furthermore, stages based on benthic foraminifers are not valid means of correlation between tectonically discrete basins of deposition. The occurrence of Subbotina patagonica (Todd) in both the Rose Canyon Shale and Cozy Dell Formation suggests time-equivalence of the two units (early middle Eocene in age). This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

A new genus and new species of Proviverrinae from the Early Eocene of Europe, Morlodon vellerei, is described. This new taxon is morphologically close to the Middle Eocene genus Matthodon, with which it shares tendencies towards a robust dentition; the two genera also share the reduction of P1. In order to examine the phylogenetic relationships of the new genus Morlodon with Early and Middle Eocene European Proviverrinae, a phylogenetic analysis of the earliest hyaenodontidans was conducted. The taxa analysed range from Late Palaeocene to Middle Eocene and are from Africa, Asia, Europe and North America. The new phylogeny of earliest hyaenodontans clarifies the systematics of the paraphyletic assemblage ‘Proviverrinae’ and results in the recognition of five major clades. The monophyly of the Limnocyoninae and Koholiinae is supported, and two new subfamilies are erected from the ‘Proviverrinae’: Sinopaninae and Arfianinae. A new definition of the Proviverrinae is proposed: only European hyaenodontidans from Early and Middle Eocene are included in this subfamily. However, the phylogenetic relationships between the five subfamilies remain to be established. An ancestral morphotype for the Hyaenodontida is proposed in order to identify the different subfamilies. On the basis of the analysis and of data presently available, an African origin for Hyaenodontida is proposed. Hyaenodontidans are involved in the faunal dispersals that occurred around the Palaeocene–Eocene (P/E) boundary. They dispersed from Africa to Asia during the Late Palaeocene (Limnocyoninae), and at the P/E boundary from Africa to Europe (Proviverrinae) and to North America through Europe (Sinopaninae and Arfianinae). Proviverrinae remain an endemic European group, whereas Sinopaninae, Limnocyoninae and Arfianinae mainly evolved in North America. Koholiinae represents the sole endemic African group. The probable African origin of the Hyaenodontida supports the diphyletism of ‘Creodonta’ and abandonment of this taxon. http://zoobank.org/urn:lsid:zoobank.org:pub:450D4FAB-42F0-4824-9DE0-DEED591C0D14

On the clay mineralogy of upper Eocene and Oligocene sediments in the Hampshire Basin

Post-collisional adakite-like magmatism in the Ağvanis Massif and implications for the evolution of the Eocene magmatism in the Eastern Pontides (NE Turkey)

The aim of this research was to interpret environmental conditions of the Pabdeh Formation in Ilam section, North West Zagros basin, based on calcareous nannoplankton. According to identified biozones which is equivalent to NP10-NP25 biozones of Martini (1971), the age of Pabdeh Formation in studied section is Early Eocene – Late Oligocene. Abundance of Discoaster and Sphenolithus in the lower part of section indicates an oligotrophic condition in sedimentary basin which is related to global warming. Toward the top of section, the Cyclicargolithus floridanus, Sphenolithus moriformis, Coccolithus pelagicus, Reticulofenestrid nannofossils are dominant. On the other hand, the presences of genera Reticulofenestra, Cyclicargolithus, Dictyococcites that are taxa of temperate and cold water, indicate mesotrophic – eutrophic conditions in the upper part of section. Increasing of Discoasters shows warming trend during the Late Oligocene time.

British Tertiary mammals are best represented in the Eocene and earliest Oligocene epochs. Additional occurrences are from the Miocene and Late Pliocene. The Eocene is marked by the occurrence of various extinct orders as well as the appearances of some of the earliest and must primitive artiodactyls and perissodactyls. The appearances in the Early Eocene and Early Oligocene represent major dispersal events, reflecting penecontemporaneous palaeogeographic changes. In the intervening timespan Britain was part of an European island, sharing its endemic terrestrial fauna. From the late Middle Eocene to earliest Oligocene, the British record is detailed enough to trace successive changes in the patterns of diversity and faunal turnover, which may relate to changing climate as well as to the dispersal events. It has been shown that changes in patterns of ecological diversity through the Eocene and earliest Oligocene match vegetational changes judged from plant fossils. They suggest a gradual transition from closed forest in the Early Eocene to a more open environment with reedmarsh and wooded patches by the end of the epoch.

Emergence of hystricognathous rodents: Palaeogene fossil record, phylogeny, dental evolution and historical biogeography

Paleocene and Eocene marine sequences distributed in Rakhi Nala and Zinda Pir Anticline areas of the eastern part of the Sulaiman Range in Pakistan record the geological history and tectonic events during the last stage of collision between the Indian and Eurasian Plates and closure of the Tethyan Ocean. The Eocene sequences consist of siltstone and mudstone with some limestone intercalations, and are divided into the Shaheed Ghat, Baska and Kirthar Formations in ascending order. We studied the Eocene biostratigraphy of planktic foraminifers in this region to reveal the geological ages of the Eocene strata based on (international) correlation with standard tropical/subtropical zones. The planktic foraminiferal assemblages are composed of 78 species of 19 different genera, including many zonal markers of tropical to subtropical regions. We identified 8 biostratigraphic zones, Zone P7, Acarinina pentacamerata Partial Range Zone, Planorotalites palmerae Total Range Zone, A. soldadoensis Assemblage Zone, Zone P12, Zone P13, Orbulinoides beckmanni-Truncorotaloides rohri Interval Zone, and Truncorotaloides rohri-Turborotalia cerroazulensis cunialensis Interval Zone in ascending order. These zones correspond to Zones P7 to P15 of tropical/subtropical schemes. However, the upper part of Zone P10 to Zone P11 is not recognized because of an interval that is barren of planktic foraminifers in the Baska Formation. The geological age of the Shaheed Ghat Formation is assigned to the Early Eocene through early Middle Eocene (Zones P7 to P10, 52.3~45.8 Ma). The Baska Formation is apparently equivalent to Zone P10 (early Middle Eocene), although its direct age is uncertain as it is barren of planktic foraminifers. The fossiliferous micritic limestone forming the lowermost part of the Kirthar Formation yielded recrystallized planktic foraminifers and calcareous nannoplankton indicating an early Middle Eocene age spanning calcareous nannoplankton Zones NP14 to NP15 (48.5~43.4 Ma), while the upper part of the Kirthar Formation ranges in age from middle Middle Eocene to early Late Eocene (Zones P12 to P15, 43.6~35.2 Ma). Hence the strata of the Kirthar Formation spans in age from early Middle Eocene through early Late Eocene based on recognition of the planktic foraminiferal Zones P10 to P15 (49~35.2 Ma).

Sedimentological and geochemical properties of authigenic carbonates in Kyushu, Japan: Implications for the transition from semi-arid to humid climate during the Eocene

Integrated biostratigraphic study of foraminifera, radiolarians, and dinoflagellates substantially improves age control of well‐exposed Late Cretaceous to late Middle Eocene (Haumurian‐Bortonian) Muzzle Group sediments at Mead Stream, inland Marlborough, New Zealand. The group, comprising 650 m of well‐bedded pelagic limestone, marl, and chert, consists of two formations: Mead Hill Formation (257 m) and Amuri Limestone (393 m). The latter includes five distinctive, informal units: Black Siltstone, Lower Limestone, Lower Marl, Upper Limestone, and Upper Marl. Muzzle Group is in fault contact with mid‐Cretaceous (Clarence Series) Split Rock Formation siltstones at its base, and is unconformably overlain by Oligocene (Landon Series) Weka Pass Limestone. The Cretaceous‐Tertiary (K‐T) boundary, within Mead Hill Formation, is marked by a distinct lithologic change from pale limestone to dark laminated mudstone grading up into a 23 m thick chert unit. Basal Paleocene biotas suggest a relatively complete boundary sequence, similar to that observed in coastal Marlborough. The Late Paleocene Black Siltstone unit, considered laterally equivalent to distinctive transgressive or highstand facies to the south and in North Island, forms the basal unit of Amuri Limestone. The overlying Lower Limestone is also Late Paleocene (late Teurian) at the base and Early Eocene (Waipawan to possibly Mangaorapan) in the upper part. The Lower Marl is Early Eocene, possibly as old as Waipawan, at the base, otherwise ii is Mangaorapan to perhaps earliest Heretaungan. The Upper Limestone is early Middle Eocene based on Radiolaria; foraminifera and dinoflagellates have not been obtained from this highly indurated unit, but indirect evidence suggesting a Heretaungan‐Porangan age is consistent with radiolarian results. All groups indicate a late Middle Eocene (Bortonian) age for the Upper Marl. Foraminifera indicate progressive transgression, with submergence from inner‐mid shelf to mid‐bathyal depths in the Cretaceous. Highly siliceous lithologies and an abundance of diatoms indicate a nutrient‐rich upwelling setting. Significant shallowing, probably within the bathyal zone, at the K‐T boundary is inferred from an increase in total abundance of benthic foraminifera and greatly reduced numbers of planktics. An influx of spumellarian radiolarians, together with increases in diatom abundance and whole‐rock silica content, indicate enhanced levels of siliceous plankton productivity, probably due to regional upwelling of cool, nutrient‐rich waters in the earliest Paleocene. Benthic‐dominated foraminiferal faunas indicate bathyal to outer shelf depths prevailed for most of the Paleocene, and planktic foraminifera only return to Cretaceous abundance levels in the latest Paleocene (Lower Limestone). Bathyal conditions are maintained throughout the remainder of the sequence. Upwelling appears to have declined progressively, with silica content and siliceous biota abundance reaching very low levels in Early‐Middle Eocene (Lower to Upper Marl).

Primitive high-K intraoceanic arc magmas of Eastern Kamchatka: Implications for Paleo-Pacific tectonics and magmatism in the Cretaceous

We present 39Ar-40Ar dating of phengite, muscovite and paragonite of samples from the HP Voltri massif (Western Alps) and from the conglomerates of the Tertiary molasses which overlie the metamorphic basement. The phengite bearing rocks analysed display peak eclogitic and blueschist facies parageneses, locally showing complex greenschist - facies replacement textures. 39Ar-40Ar dating of white micas yielded Eocene ages interpreted as the time of different metamorphic equilibrations. In particular, high-Si phengites from eclogite clasts record a ca. 49 Ma age for the eclogite peak and ca. 43 Ma for the blueschist retrogression; phengites from a blueschist basement sample record a ca. 40 Ma for the metamorphic peak; low-Si muscovite from a metasediment dates the formation of the greenschist paragenesis at ca. 33 Ma. The internal discordance of age spectra is proportional to the chemical complexity of the micas. Our data document that the rock samples analyzed reached peak HP conditions at different times over a time - span of ca. 10 Ma. The subduction to peak blueschist conditions is in fact still going on during the exhumation of higher-pressure, eclogite-facies rocks. Our results therefore fit a tectonic model with different ophiolitic slices subducted at different moments, over a time span ranging from Lower Eocene until the Eocene-Oligocene boundary. This implies that the subduction and exhumation processes occurred simultaneously, allowing the uprising HP-rocks to escape termal reequilibration. Our data require a decoupling of exhumation from erosion: exhumation was largely accomplished before significant erosion of the wedge. Initially, it was likely driven by the buoyancy effect of antigorite serpentinites; subsequently it may have been associated with the development of blueschist shear zones. Fast exhumation was not accompanied by a high uplift of the mountain chain, whose erosion and input into the sedimentary basin occurred more than 10 Ma later.

We map the spatial and temporal distribution and depositional environments of Eocene sequences and formations in the New Jersey Coastal Plain, USA, using an array of coreholes and gamma logs. On this passive margin, Eocene depositional systems reflect a change from prograding earliest Eocene mud lobes, to early to middle Eocene hemipelagic ramp, and finally to late middle Eocene prograding sandy sequences. The Marlboro Clay, containing the Paleocene–Eocene Thermal Maximum (PETM), was deposited as prograding fluid mud during times of high global temperatures; it is found in northern and southern lobes but is absent from the central coastal plain. Lower and lower middle Eocene sediments consist of carbonate-rich clays (“marls”) deposited in middle to outer neritic (50–150 m) paleodepths on a hemipelagic ramp during a peak in global mean sea level. Exceptionally deep early Eocene deep water depths compared to other regions are attributed to mantle dynamic topography. The upper middle to upper Eocene consists of three prograding lithologic units found in parallel belts with coarse-grained sediments in the most updip positions and fine-grained sediments found in the most downdip positions; the lithologic units transgress time and sequences. Comparison of the timing of sea-level falls constructed using oxygen isotopes with New Jersey Eocene sequence boundaries shows a correlation between sequences boundaries and global mean sea-level falls controlled by ice-volume changes, even in the purportedly ice-free early Eocene. We date the change from ramp to prograding sequences to the late middle Eocene (ca. 41.5 Ma). We use a forward stratigraphic model to evaluate the primary controls influencing changing styles of sedimentation on the Eocene New Jersey margin. Our forward stratigraphic model shows that the appearance of prograding sands and silts in the middle Eocene is a response primarily to changes in siliciclastic input, presumably due to climate or tectonics in the hinterland. Our study of the New Jersey Eocene shows that by integrating stratigraphic and chronostratigraphic data with an independent estimate of global mean geocentric sea level, our forward model was able to disentangle the effects of sea level and sediment supply on the stratigraphic record.