Deep-sea benthonic foraminiferal faunal turnover near the Eocene/Oligocene boundary

Eocene-Oligocene deep-sea benthonic foraminifera in D.S.D.P. Site 277 in the southwest Pacific have been analyzed to determine the benthonic foraminiferal response to the development of the psychrosphere near the Eocene/Oligocene boundary. Biostratigraphic ranges of 41 taxa show that 23 taxa are found throughout the Late Eocene to Early Oligocene sequence, while 18 taxa exhibit first or last occurrences. Comparison of the faunal changes in Site 277 with a benthonic foraminiferal oxygen isotope record shows that the development of the psychrosphere did not have a profound effect upon the benthonic foraminifera, and the overall faunal change preceding and subsequent to the bottom-water circulation event occurred gradually. The inferred water-mass event affected the relative abundance of one species, Epistominella umbonifera. The lack of major faunal changes at the Eocene/Oligocene boundary in Site 277 probably reflects either wide environmental tolerances of the benthonic foraminifera, or a bottom-water temperature change less than 3°C.Examination of previously published benthonic foraminiferal biostratigraphic data from D.S.D.P. Sites 167, 171, 357, 360, 363, and 400A, and deep-sea ostracode data from D.S.D.P. Leg 3 show faunal changes occurred during discrete intervals in the Middle Eocene-Early Oligocene. The faunal patterns from these data and from Site 277 show that the Eocene/Oligocene cooling event did not cause rapid, catastrophic changes of the benthonic faunas of the open ocean, although significant faunal changes are associated with the water mass event in Sites 167, 171 and 400A.The benthonic faunal changes in Middle Eocene-Early Oligocene time are consistent with the gradual decrease of inferred bottom-water temperatures, based on previously published oxygen isotopic data. The δ ¹⁸O Eocene/Oligocene enrichment of 0.76‰ is a major event in the Southern Ocean oxygen isotopic record, but is considerably less in magnitude than the 1.75-2.00‰ change that occurred gradually from mid-Early Eocene to the Eocene/Oligocene boundary. The benthonic foraminiferal and isotopic data indicate that bottom-water circulation may have developed during the Middle Eocene to Early Oligocene interval, with the 3°C bottom-water cooling near the Eocene/Oligocene boundary representing part of this development.     

Palaeogene isotopic temperatures of western India

Oxygen isotopic measurements of larger benthic foraminifers from western India suggest that the Palaeogene temperature varied between 22deg;C and 32deg;C in this region. The warm climate of the Palaeocene and the Early Eocene, hovering around 32°C, deteriorated in late Middle Eocene (corresponding to planktic zones P13-P14) when the temperature dropped by 6deg;C. With progressive cooling through the Late Eocene, the temperature reached 22deg;C during Early Oligocene times. The cooling trend set in the Middle Eocene seems to have been terminated towards the end of the Palaeogene when the temperature rose to 25°C. □ Palaeotemperature, Palaeogene, oxygen isotopes, larger foraminifiers, India.     

Biochronology and paleoclimatic implications of Middle Eocene to Oligocene planktic foraminiferal faunas

Planktic foraminiferal assemblages have been analyzed quantitatively in six DSDP sites in the Atlantic (Site 363), Pacific (Sites 292, 77B, 277), and Indian Ocean (Sites 219, 253) in order to determine the nature of the faunal turnover during Middle Eocene to Oligocene time. Biostratigraphic ranges of taxa and abundance distributions of dominant species are presented and illustrate striking similarities in faunal assemblages of low latitude regions in the Atlantic, Pacific and Indian oceans. A high resolution biochronology, based on dominant faunal characteristics and 55 datum events, permits correlation between all three oceans with a high degree of precision. Population studies provide a view of the global impact of the paleoclimatic and paleoceanographic changes occurring during Middle Eocene to Oligocene time.Planktic foraminiferal assemblage changes indicate a general cooling trend between Middle Eocene to Oligocene time, consistent with previously published oxygen isotope data. Major faunal changes, indicating cooling episodes, occur, however, at discrete intervals: in the Middle Eocene 44-43 Ma (P13), the Middle/Late Eocene boundary 41-40 Ma ( ), the Late Eocene 39-38 Ma ( ), the Eocene/Oligocene boundary 37-36 Ma (P18), and the Late Oligocene 31-29 Ma ( ). With the exception of the boundary, faunal changes occur abruptly during short stratigraphic intervals, and are characterized by major species extinctions and first appearances. The Eocene/Oligocene boundary cooling is marked primarily by increasing abundances of cool water species. This suggests that the boundary cooling, which marks a major event in the oxygen isotope record affected planktic faunas less than during other cooling episodes. Planktic foraminiferal faunas indicate that the boundary event is part of a continued cooling trend which began during the Middle Eocene.Two hiatus intervals are recognized in low and high latitude sections at the Middle/Late Eocene boundary and in the Late Eocene ( ). These hiatuses suggest that vigorous bottom water circulation began developing in the Middle Eocene, consistent with the onset of the faunal cooling trend, and well before the development of the psychrosphere at the boundary.     

Palaeogene palaeobiogeography of the Indian subcontinent

Certain palaeoecological criteria in the reconstruction of the Palaeogene palaeobiogeography of the Indian subcontinent are discussed. The Early Palaeogene is characterised by marine oscillations, a prolific invertebrate fauna, extensive coal facies development and outpouring of basaltic lava flows, the last being a feature connected with the movement of the Indian Plate and coinciding with a Himalayan orogenic impulse. The Middle Eocene transgression marks the transition of marine sedimentation to fluvial conditions in northern India with the presence of a fairly diverse mammalian fauna in northwestern Pakistan and northern India. During the Late Oligocene, mammals clearly ancestral to the much more prolific Siwalik fauna were present in western Pakistan, northeastern India and southcentral Burma.The flora consists of mainly tropical to subtropical families with the addition of some temperate elements in Assam in the latter half of the Eocene and Oligocene. Invertebrates indicate a close affinity between the western and eastern sectors and suggest that the sea was continuous in the north at least up to the Palaeocene. With the emergence of land in the northeastern part of the subcontinent, the fauna of Assam acquired distinct Indo-Pacific elements similar to those of Burma and the Indonesian Arc. Later, the sea was divided into two gulfs which gradually shrank towards the end of the Palaeogene and disappeared by the Middle Miocene.     

Palaeoceanographical changes recorded by Cenozoic deep-sea ostracod assemblages from the South Atlantic and the Southern Ocean (ODP Sites 1087 and 1088)

Cenozoic palaeoceanography of the SE Atlantic and Southern Oceans has been investigated using Late Eocene/Early Oligocene to Quaternary ostracod assemblages from 49 samples of ODP Sites 1087 and 1088. Although the overall abundance of ostracods is relatively low (means of 17 and 49 specimens per sample at Sites 1087 and 1088, respectively) and there is an apparently high level of endemism (ranging from 50% to 80% at Sites 1087 and 1088), three major changes in the faunal assemblages are identified at Site 1087 (denoted A, B and C) and two at Site 1088 (denoted B' and C'). The assemblage boundaries, detected on the basis of stepwise changes in the abundance, diversity, dominance, endemism, faunal turnover and relative abundance of common taxa, coincide broadly with previously identified, ostracod-based palaeoceanographical 'events' discussed by Benson and co-workers over the last two decades. The data do not extend sufficiently far back to record the initiation of Assemblage A, but the faunal change between Assemblages A and B, marked by a decline in abundance, species diversity and faunal turnover, occurs within the Middle Miocene (NN5-6). It coincides with a previously documented palaeoceanographical 'event' at 16-14 Ma which, we suggest, may be related to the initiation of North Atlantic Deep Water (NADW) production and/or an expansion of the East Antarctic ice sheet. Assemblage B' is subdivided into the two Sub-assemblages B'¹ and B'² mainly on the basis of an increase in diversity, a peak in faunal turnover and a drop in the relative abundance of the genus Krithe in early Late Miocene time (NN9, c. 10.5 Ma). The B'¹/B'² Sub-assemblage boundary cannot be related to any previously documented faunal change in deep-sea ostracods. Changes associated with the boundaries between Assemblages B and C, and B' and C', which we believe to be synchronous, both include a decrease in diversity and abundance. In addition, two strong turnover peaks occur near the B'/C' boundary at Site 1088. The B/C and B'/C' boundaries coincide with a previously documented midPliocene 'event' (3.5 Ma) (NN15-16) which may be linked to putative closure of the Straits of Panama and increased production of NADW, the latter in turn leading to increased production of Antarctic Intermediate Water (AAIW) and Antarctic Bottom Water (AABW). Alternatively, fiuctuations in size of the Antarctic ice sheet during possible Pliocene warm periods could indirectly be responsible for the observed midPliocene faunal changes.     

Eocene–Oligocene calcareous nannofossils from Maud Rise and Kerguelen Plateau (Antarctica): paleoecological and paleoceanographic implications

The evolution of the Southern Ocean climate during the late Eocene–late Oligocene interval is examined through high-resolution, quantitative calcareous nannofossil analyses on samples from the Southern Ocean sections on Maud Rise and Kerguelen Plateau. We determined the abundance patterns of the counted species to clarify the biostratigraphy, which we correlated with high-resolution magnetostratigraphy [Roberts, A.P., Bicknell, S.J., Byatt, J., Bohaty, S.M., Florindo, F., Harwood, D.M., 2003a. Magnetostratigraphic calibration of Southern Ocean diatom datums from the Eocene–Oligocene of Kerguelen Plateau (Ocean Drilling Program Sites 744 and 748). In: Florindo, F., Cooper, A.K., O'Brien, P.A. (Eds.), Antarctic Cenozoic Palaeoenvironments: Geologic Record and Models. Palaeogeogr., Palaeoclimatol., Palaeoecol. 198 145–168; Florindo, F., Roberts, A.P., in press. Eocene–Oligocene magnetobiochronology of ODP Sites 689 and 690, Maud Rise, Weddell Sea, Antarctica. Geol. Soc. Am. Bull.], and used this data to interpret paleoceanographic changes through the late Eocene to late Oligocene. Percentage plots of the individual species, compared with R-mode principal component and cluster analysis results, allowed us to divide the assemblages into three groups: temperate-water taxa, cool-water taxa, and no temperature-affinity taxa. We attempt correlations between these paleoecological groups and the major sea-surface temperature (SST) variations with tectonic and paleoceanographic changes in the Southern Ocean. During the late Eocene, the nannofossil assemblage data reveal that there were several minor SST decreases (coolings) from 36 to 34 Ma, before the Eocene/Oligocene (E/O) boundary. A sharp cooling event, dated at 33.54 Ma (earliest Oligocene), occurred about 160 kyr after the E/O boundary, which is dated at 33.7 Ma. Relatively stable, cool conditions are interpreted to persist until the latest Oligocene, when an increase in abundance of temperate-water taxa, which corresponds to an antithetical decrease in abundance of cool-water indicators, is recorded.On the basis of our dating, the opening of the Drake Passage, allowing shallow-water circulation, began by 33.54 Ma at the latest, while the establishment of deep-water connections through the Tasmanian Gateway occurred at 33 Ma, as suggested by Exon et al. [Proc. ODP, Init. Rep. 189 (2001) 1].     

British mammals in the Tertiary period

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.     

Major vegetation trends in the Tertiary of Patagonia (Argentina): A qualitative paleoclimatic approach based on palynological evidence

The patterns of Patagonian vegetation change suggest a strong relationship between the major thermal characters of the flora and the global paleoclimatic trends during Tertiary times. This conclusion was reached from the assessment of fossil pollen data from Patagonia throughout the Paleogene and Early Neogene periods and the subsequent comparison of palynological data to the global deep-sea oxygen isotope record. Four main time intervals were recognized based on the temporal distribution of selected angiosperm key taxa. (1) Paleocene to Early Eocene: presence of megatherm elements (e.g. Nypa, Pandanus), probably integrating mangrove communities in Patagonian lowlands. (2) Middle Eocene to Early Oligocene: rise to dominance of mesotherm and microtherm Nothofagus species. Megatherm taxa were well recorded at the beginning of this interval (e.g. Ilex) but were shown to disappear towards the end. (3) Late Oligocene to Middle Miocene: new increases of megatherm taxa such as palms, Cupania and Alchornea. First occurrences of mesotherm Asteraceae, represented by trailing Mutisieae, were reported. (4) Late Miocene: dispersal of meso-microtherm and arid adapted taxa (e.g. Ephedraceae and Asteraceae) across the non-Andean region of Patagonia. Microtherm Nothofagacean forests probably occurred on the higher rainfall regions of western Patagonia. The current vegetation was most likely reached during this last stage with the forest development under wetter conditions on the Andean sectors, and the steppe throughout the non-Andean region of Patagonia.     

Eocene -Oligocene paleoceanography of the deep Bay of Biscay: Benthic foraminiferal evidence

A major change in benthic foraminiferal assemblages occurred in the deep Bay of Biscay (> 3 km water; DSDP Sites 119, and Site 400A) between early middle Eocene and earliest Oligocene. Predominant Eocene deep-sea taxa (Nuttallides truempyi, Clinapertina spp., Abyssamina spp.) and associated rarer species became extinct in this interval. These extinctions were followed by an increase in abundance of bathymetrically wide-ranging and stratigraphically long-ranging taxa: Globocassidulina subglobosa, Oridorsalis spp., Gyroidinoides spp., and the Cibicidoides ungerianus plexus. The extinctions cannot be dated precisely from the stratigraphic record recovered to date in the Bay of Biscay; however, the replacement of the N. truempyi-dominated assemblage has been noted previously in the deep South Atlantic/Caribbean as occurring near the middle/late Eocene boundary. Other than the decrease in abundance and extinction of N. truempyi, no major abundance changes are noted within the Eocene at the shallower Site 401 (～ 2 km water) in the Bay of Biscay. During the Oligocene, Nuttallides umbonifera replaced the Eocene species N. truempyi as the predominant deep-sea benthic foraminifera, reaching peak abundance in the middle Oligocene at Sites 119 and Site 400A. In the modern oceans, the abundance ot N. umbonifera is positively correlated with increased corrosiveness of bottom water, while at Site 119 the abundance of Nuttallides spp. is negatively correlated with δ ¹³C values in benthic foraminifera. As lower δ ¹³C values are often associated with older water masses, large numbers of Nuttallides spp. are thought to reflect older, and more corrosive bottom water. The faunal data and oxygen and carbon isotopic data are compared with a circulation model derived from North Atlantic seismic stratigraphic studies to show that old, warm, corrosive, and sluggish Eocene bottom water was replaced by younger, colder, less corrosive, more vigorously circulating bottom water of northern origin by the early Oligocene. Faunal and isotopic data suggest that bottom water became older and more corrosive again in the middle Oligocene, reflecting a reduction in circulation that can also be inferred from the seismic record in the nearby Rockall Plateau region.     

Middle Eocene–Early Pliocene Subantarctic planktic foraminiferal biostratigraphy of Site 1090, Agulhas Ridge

The analysis of planktic foraminiferal assemblages from Site 1090 (ODP Leg 177), located in the central part of the Subantarctic Zone south of South Africa, provided a geochronology of a 330-m-thick sequence spanning the Middle Eocene to Early Pliocene. A sequence of discrete bioevents enables the calibration of the Antarctic Paleogene (AP) Zonation with lower latitude biozonal schemes for the Middle–Late Eocene interval. In spite of the poor recovery of planktic foraminiferal assemblages, a correlation with the lower latitude standard planktic foraminiferal zonations has been attempted for the whole surveyed interval. Identified bioevents have been tentatively calibrated to the geomagnetic polarity time scale following the biochronology of Berggren et al. (1995). Besides planktic foraminiferal bioevents, the disappearance of the benthic foraminifera Nuttallides truempyi has been used to approximate the Middle/Late Eocene boundary. A hiatus of at least 11.7 Myr occurs between 78 and 71 m composite depth extending from the Early Miocene to the latest Miocene–Early Pliocene. Middle Eocene assemblages exhibit a temperate affinity, while the loss of several planktic foraminiferal species by late Middle to early Late Eocene time reflects cooling. During the Late Eocene–Oligocene intense dissolution caused impoverishment of planktic foraminiferal assemblages possibly following the emplacement of cold, corrosive bottom waters. Two warming peaks are, however, observed: the late Middle Eocene is marked by the invasion of the warmer water Acarinina spinuloinflata and Hantkenina alabamensis at 40.5 Ma, while the middle Late Eocene experienced the immigration of some globigerinathekids including Globigerinatheka luterbacheri and Globigerinatheka cf. semiinvoluta at 34.3 Ma. A more continuous record is observed for the Early Miocene and the Late Miocene–Early Pliocene where planktic foraminiferal assemblages show a distinct affinity with southern mid- to high-latitude faunas.     

Paleocene-Pleistocene benthic foraminiferal evidence of major paleoceanographic events in the eastern South Atlantic (DSDP Site 525, Walvis Ridge)

Benthic foraminifers in the size-fraction greater than 0.073 mm were studied in 88 Paleocene to Pleistocene samples from Deep Sea Drilling Project Site 525 (Hole 525A, Walvis Ridge, eastern south Atlantic). Clustering of the samples on the basis of the 86 most abundant foraminifers (in total, 331 taxa were identified) allowed separating two major assemblage zones: the Paleocene to Eocene interval, and the Oligocene to Pleistocene interval. Each of these, in turn, were subdivided into three minor subzones as follows: lower upper Paleocene (approx. 62.4 to 57.8 Ma); upper upper Paleocene (56.6 to 56.2 Ma); lower and middle Eocene (55.3 to 46.8 Ma); upper Oligocene to middle Miocene (25.3 to 16 Ma); middle Miocene to Pliocene (15.7 to 4.2 Ma); and lower Pleistocene (0.4 to 0.02 Ma), with only minor differences with the previous zone. Some very abundant taxa span most of the column studies (Bolivina huneri, Cassidulina subglobosa, Eponides bradyi, E. weddellensis, Gavelinella micra, Oridorsalis umbonatus, etc.). Several of the faunal breaks recorded coincide with conspicuous minima in the specific diversity curve, thus suggesting that the corresponding turnovers signal the final stages of periods of faunal impoverishment. At least one major bottom-water temperature drop (as derived from δ¹⁸O data) is synchronous with a decrease in the foraminiferal specific diversity. On the other hand, a specific diversity maximum in the middle Miocene might be associated with a δ¹³C increase at approx. 16 to 12 Ma. Highest foraminiferal abundances (up to 600–800 individuals per gram of dry sediment) occurred in the late Paleocene and in the early Pleistocene, in coincidence with the lowest diversity figures calculated. The magnitude of the most important faunal turnover recorded, between the middle Eocene and the late Oligocene, is magnified in our data set by the large hiatus which separates the middle Eocene from the upper Oligocene sediments. Considerably smaller overturns occurred within the late Paleocene (in coincidence with changes in the specific diversity, absolute abundance of foraminiferal tests, and δ¹³C), and in the middle Miocene (in coincidence with a specific diversity maximum and a δ¹³C excursion). New information on the morphology and the stratigraphic ranges of several species is furnished. For all the taxa recorded the number of occurrences, total number of individuals identified and first and last appearances are listed.     

COMPARISONS BETWEEN PALAEOCENE–EOCENE PARATROPICAL SWAMP AND MARGINAL MARINE POLLEN FLORAS FROM ALABAMA AND MISSISSIPPI, USA

Abstract:  Climate warming at the Palaeocene/Eocene boundary ( c . 55.8 Ma) had significant permanent affects on paratropical and warm-adapted vegetation types. Pollen and spore records which document vegetation turnover from the eastern US Gulf Coast have all been taken from sediments of marginal marine depositional environments. Pollen and spores (sporomorphs) are preserved excellently in these marginal marine depositional environments but these assemblages contain grains transported from many different vegetation types and over huge geographic distances. Currently it is unclear whether the turnover from important paratropical areas like the US Gulf Coast is a reflection on actual vegetation change in the local region or from source areas far away in the continental interior. Sporomorph data from 20 former swamps (lignites) from the Nanafalia, Tuscahoma and Hatchetigbee formations in Mississippi and Alabama, USA, are used to test the fidelity of the marine sporomorph record across the Palaeocene–Eocene transition. Data show that extinction is noted in the swamp record (≥7 per cent of Palaeocene taxa) and that swamps were susceptible to immigration in the Early Eocene with the first occurrences of Brosipollis spp. (Burseraceae), Dicolpopollis spp. (Palmae), Nuxpollenites psilatus (Loranthaceae) and Platycarya spp. (Juglandaceae). Swamps have higher within-sample diversity in the Eocene but higher among-sample diversity in latest Palaeocene–earliest Eocene samples, which parallels exactly diversity trends estimated from marine sporomorph assemblages. Palms also increase in abundance in the Eocene. The swamp data demonstrate that the flora growing in these ancient paratropical forests was diverse ( c. 120 taxonomic groups) but incorporated an unusual admixture of plants with modern tropical affinities together with those that now live in modern temperate to subtropical North America.     

Wasatchian (Early Eocene) pollen floras from the Red Hot Truck Stop, Mississippi, USA

Sediments at the Red Hot Truck Stop (RHTS), Mississippi, USA are important because they contain the lowest latitude record of both the earliest known Eocene plant and mammal fossils in North America. The RHTS contains the uppermost Tuscahoma Formation and the lowermost part of the basal Bashi and Hatchetigbee formations. The Tuscahoma Formation is composed of glauconitic sands and silts that represent estuarine to shallow marine sediments. Faunal remains indicate that the RHTS section belongs to the Wasatchian North American land mammal age and specifically to the lower Graybullian subdivision. Pollen and spore floras from the RHTS are moderately diverse (113 taxa) and contain families that today are associated with warm‐adapted vegetation types such as Annonaceae, Bombacaceae, Burseraceae and palms. Eocene first occurrences are represented by Brosipollis sp., Celtispollenites sp., Interpollis microsupplingensis, cf. Nuxpollenites psilatus, Platycarya spp., Retistephanocolporites sp. and Symplocos? contracta and by one genus of pteridophyte spore (Granulatisporites sp.). The overall composition and within‐sample diversity of the sporomorph flora is more similar to the Hatchetigbee Formation (early Eocene) than to the middle Tuscahoma Formation (late Palaeocene) but among‐sample diversity remains unchanged across the Palaeocene/Eocene boundary. The distinct composition of the RHTS demonstrates that floral change across the Palaeocene/Eocene boundary is complex and composed of several phases of floral change.     

The fossil history of palms (Arecaceae) in Africa and new records from the Late Oligocene (28–27 Mya) of north-western Ethiopia

The African palm fossil record is limited but the data provide an outline of palm evolution from the Late Cretaceous through the Neogene. Pollen attributed to palms is reported from the Aptian (125–112 Mya), but the earliest unequivocal record in Africa is Campanian (83.5–70.6 Mya). Palms diversified 83.5–65.5 Mya and became widespread, although most records are from the west and north African coasts. Many taxa were shared between Africa and northern South America at that time, but a few were pantropical. Extirpations occurred throughout the Palaeogene, including a notable species turnover and decline at the Eocene–Oligocene boundary (33.9 Mya), a change that resulted in the elimination of nypoid palms from Africa. The Neogene plant macrofossil record is better sampled than the Palaeogene, although few palms are documented. Thus, the low diversity of African palms today is more likely the result of Palaeogene, rather than Neogene extinctions. Newly discovered palm fossils of leaves, petioles and flowers from the Late Oligocene (27–28 Mya) of north-western Ethiopia document the abundance and dominance of palms in some communities at that time. The fossils represent the earliest records of the extant genera Hyphaene (Coryphoideae) and Eremospatha (Calamoideae).  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 69–81.     

伊朗卡尚地区古近纪介形类的发现

本文简要报道了发现于伊朗卡尚地区古近系的介形类,计16属6种、8比较种、9未定种及1亲近种。根据介形类化石组合面貌,并结合钙质超微、沟鞭藻和有孔虫化石组合,认为含介形类化石的地层时代为始新世至渐新世,推测其沉积环境为正常浅海大陆架环境,而且为温暖浅海内陆架。     

Middle Eocene Ostracods from southeast Fayoum area,Egypt: Systematics,paleobathymetry and paleobiogeography

This study deals with the Middle Eocene ostracods from southeast Fayoum area, Egypt. To carry out this investigation, three outcrops are examined, Gebel Elwe El Breig, Gebel Sath El Hadid and Gebel Munqar El-Shinnara. This study is based on the Midawara Formation that consists mainly of fossiliferous limestone, marly limestone and clay. The studied ostracod assemblage includes thirty-one species and subspecies, belonging to twenty-three genera and seventeen families. The ostracod group belonging to Cytheroidea Baird, 1850 represents the most abundant group that reaches 81.99% in Munqar El-Shinnara section, 81.88% in Sath El Hadid section, and 61.12% in Elwe El Breig section. The structure of the investigated assemblages (abundance of ostracods, number of taxa, Fisher's alpha, Shannon index, and equitability) indicates deposition in an environment belonging to the neritic zone. Moreover, this study tries to use the multivariate analyses to distinguish the paleobiogeographic provinces in Tethyan region during the Middle Eocene. These analyses are applied on a matrix consists of some nominated Middle Eocene species from 13 countries. The results point to two distinctive provinces, Southern Tethys Province (Algeria, Tunisia, Libya, Egypt and Jordan) and the Northern Tethys Province (England, Germany, Spain, France, Belgium, Ukraine, Hungary and Turkey). The reasonable similarities between these provinces may reflect a possible connection between both sides of the Tethys during the Middle Eocene age.     

Facies dynamics in Eocene to Oligocene circumalpine carbonates

A new concept, termed ‘Facies Dynamics’ (defined as changes of specific carbonate facies types in time and space, which are controlled by phylogenetic, ecological and geological parameters), is introduced. This concept aims to define and interpret spatial and temporal changes of carbonate facies patterns. It is based on Middle Eocene to Early Oligocene shallow-water carbonate facies types from the circumalpine area (north-eastern Italy, northern Slovenia, Austria and southern Bavaria), which are compared with respect to dominating biogenic components and their distributions along a shelf gradient. This comparison has lead to the distinction and definition of 14 Major Facies Types (MFTs), which are dominated by coralline algae, larger and smaller foraminifera, corals and bryozoans. The presence and distribution of these MFTs from three different time slices (Middle Eocene, Late Eocene and Early Oligocene) is compared. Nine aspects of facies dynamics are distinguished: origination, extinction, immigration, emigration, expansion, reduction, stasis, shift, and replacement of MFTs. These changes are controlled by regional changes in ecological parameters, but also by global events, especially extinction patterns at the Middle/Late Eocene boundary and at the Eocene/Oligocene boundary.     

A new genus and species of triggerfish from the Middle Eocene of the Northern Caucasus,the earliest member of the Balistidae (Tetraodontiformes)

Until now, the earliest known members of the triggerfish family Balistidae have been two genera from the Oligocene. Herein is described the new balistid Gornylistes prodigiosus gen. et sp. nov. from the uppermost Middle Eocene (Kuma Horizon) of the Northern Caucasus (Gorny Luch locality); it is as thoroughly modern in its bauplan as the taxa of balistids from the Oligocene and more recent periods, and far more advanced morphologically than the several stem taxa of the balistoid + ostracioid clade known from earlier in the Middle and Lower Eocene and from the Upper Paleocene.     

Earliest South American paucituberculatans and their significance in the understanding of ‘pseudodiprotodont’ marsupial radiations

We describe the oldest Paucituberculata marsupials, from the La Barda and Las Flores localities (Argentina; Late Palaeocene, and Early–Middle Eocene), as well as from the Itaboraí Basin (Brazil; Late Palaeocene). The new taxa are represented by very scarce, although well‐preserved, dental remains. A parsimony analysis was performed in order to evaluate the phylogenetic affinities of these taxa. Representatives of both Riolestes capricornicus gen. et sp. nov. and Bardalestes hunco gen. et sp. nov. appear to be basal paucituberculatans, and their molar features give clues on the early evolution of the representatives of this order. Within the Paucituberculata we recognize two major clades: Caenolestoidea and Palaeothentoidea. We conclude that ‘pseudodiprotodont’ marsupials of the traditional literature (i.e. Polydolopimorphia + Paucituberculata) do not form a natural group. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 867–884.