Late Paleocene Age Research Articles

ПАЛЕОЦЕНОВЫЕ ОТЛОЖЕНИЯ ВОЗВЫШЕННОСТИ ЯМАТО (ЯПОНСКОЕ МОРЕ) И УСЛОВИЯ ИХ ОБРАЗОВАНИЯ

A micropaleontological study of the oldest sediments of the Cenozoic sedimentary cover of the Sea of Japan, found on the Yamato Rise, allowed us to identify the palynological assemblage of the late Paleocene age (59.2–56.0 Ma) and refine the age of the host sediments. The findings of exclusively marine microfossils (diatoms and silicoflagellates) in these sediments, the high content of geochemical indicators of paleosalinity (B, B/Ga) in them, the chemical composition of autigenic minerals, as well as the presence of organic remains close to seaweed in them, prove the marine genesis of these deposits. It is assumed that sedimentation occurred on the periphery of the epicontinental shallow sea basin under climate conditions close to subtropical.

A Late Paleocene age for Greenland's Hiawatha impact structure.

The ~31-km-wide Hiawatha structure, located beneath Hiawatha Glacier in northwestern Greenland, has been proposed as an impact structure that may have formed after the Pleistocene inception of the Greenland Ice Sheet. To date the structure, we conducted 40Ar/39Ar analyses on glaciofluvial sand and U-Pb analyses on zircon separated from glaciofluvial pebbles of impact melt rock, all sampled immediately downstream of Hiawatha Glacier. Unshocked zircon in the impact melt rocks dates to ~1915 million years (Ma), consistent with felsic intrusions found in local bedrock. The 40Ar/39Ar data indicate Late Paleocene resetting and shocked zircon dates to 57.99 ± 0.54 Ma, which we interpret as the impact age. Consequently, the Hiawatha impact structure far predates Pleistocene glaciation and is unrelated to either the Paleocene-Eocene Thermal Maximum or flood basalt volcanism in east Greenland. However, it was contemporaneous with the Paleocene Carbon Isotope Maximum, although the impact’s exact paleoenvironmental and climatic significance awaits further investigation.

Palyno-Stratigraphy and Kerogen Assessment of OMA Well Sediments, Offshore Dahomey Basin, Southwestern Nigeria

Biostratigraphy has remained a tool for basin and environmental reconstruction in sedimentology. This study aims to further delineate and classify the lithology, environment of deposition, and the biozonation of microorganisms found in the studied well. Thirty-four (34) ditch cutting samples from OMA well, offshore Dahomey Basin, were considered for their textural and palynomorphs/palynofacies characterization. The samples were observed and processed according to the standard palynological procedure for geologic samples using hydrochloric and hydrofluoric acid digestion. The stratigraphic sequence of the well ranges from shale to sandstone to argillaceous sandstone. The shales appear highly fissile and laminated in all shades of grey and black while the sandstone colour ranges from light-grey/brown to brown and very deep brown. The sandstone contains some mica flakes and likely pyrites in fine-medium, sub-angular to rounded grains. A total of 28 diverse palynomorphs were reported from the palynological analysis with low abundance. The low recovery of pollens was likely due to limited terrestrial influence and the reasonable amount of dinoflagellate cysts and microforaminifera wall present indicated a marginal marine to a distal offshore environment. Two zones correlated for this study are Danea mutabilis (Early Paleocene) and Dinogymnium euclaense (Upper Maastrichtian) zones. Palynomaceral classifications through visual, microscopic kerogen assessment resulted in high preservation of organic matter which suggests a reducing environment of deposition. The dominances of 48% amorphous (I), and 36% exinite (II), with a considerable amount of the 5% vitrinite (III), and 11% inertinite (IV) kerogen types, indicate that the organic matter is mainly sapropelic and mixed humic-sapropelic types which are favorable for hydrocarbon generation and primarily of marine origin. The spores/pollen colour ranges from light yellow/brown, brown transitioning into darker brown on a scale of 4/5 transitioning to 5/6. Medium degree of maturation (4/5) to late degree (6/7) of maturation was inferred. The studied interval of the OMA well sediments agrees with the established stratigraphic interval of the offshore, Dahomey basin, within the Upper Maastrichtian to Late Paleocene age range and supports high preservation of organic matter sufficient and mature enough to generate hydrocarbon.

Age, microfacies and depositional environment of the Middle to Late Paleocene shallow-marine carbonates in the Sirt Basin of Libya (Upper Sabil Formation): \u201cAre Intisar domal structures pinnacle reefs?\u201d

In the central-eastern Sirt Basin, enigmatic Intisar domal structures host significant hydrocarbon accumulations. These structures have been commonly interpreted as pinnacle reefs/bioherms occurring in the open-marine basinal environment. Generally, pinnacle reefs/bioherms are mainly characterized by in situ carbonates. The current study challenges the Intisar pinnacle reef/bioherm model by examining one of the domal structures in terms of biostratigraphy, microfacies and depositional environment. These structures were dated using larger benthic foraminifera, which yielded a Middle to Late Paleocene age (Selandian–Early Thanetian). Thirteen microfacies types representing different carbonate ramp environments ranging from outer ramp to inner ramp, were defined. Outer ramp deposits have been observed adjacent to the domal structure, represented mainly by wackestone with small benthic and planktonic foraminifera. The outer ramp deposits are most likely isochronous to the domal structures. The lower part of the domal structures is composed mainly of foraminiferal–algal–echinodermal packstones. The upper part is characterized by foraminiferal–algal–echinodermal packstones with intercalated microbialite–coral boundstones. The euphotic inner ramp deposits are preserved on the crest of the domal structure, consisting of grainstone and packstone rich in Glomalveolina. As a result of this study, the Intisar domal structures are seen as erosional relics of a carbonate ramp and no evidence for pinnacle reef/bioherm model was found.

Biostratigraphy and Sequence Stratigraphy and Depositional Environment of Kolosh Formation in Dohuk Area, Northern Iraq

The present study deals with biostratigraphy, depositional environment and sequence stratigraphy of Kolosh Formation in two sections of Bekher anticline, northeastern Iraq by using the planktonic and benthonic foraminifera. Therefore, (48) species of planktonic foraminifera belonging to (14) genera and (34) species of benthonic foraminifera belonging to (19) genera have been recognized. The detailed planktonic foraminiferal investigation permits the recognition of seven well defined biozones and three subzones; they indicate that Kolosh Formation extends from the Early Paleocene (Danian) to Late Paleocene (Thanetian) age. The depositional environment of the formation was studied throughout relying on the variation in the diversity of planktonic forminifera, as well as throughout the ratio of the planktonic foraminifera to the whole mass of foraminifera, and the ratio of planktonic forminifera to the benthonic formiminifera. The lower part of the formation represents the upper bathyal environment, while the middle part deposited within the outer shelf environment, then deposition basin became within the middle shelf area in the upper parts of the formation. Sequence stratigraphic analysis for the studied sections of Kolosh Formation delineated three sequences which is interpreted as 3rd order sequences, and it is found that the deposition of Kolosh Formation in the Badi section had been occurred in shallower level for most sedimentation intervals compared to the Linwa section which represents a somewhat deeper marine environment.

Morphology and Affinities of Ampelocissites Seeds (Vitaceae: Ampelopsis clade) from the Paleogene of Texas, USA

Abstract—The type material on which the fossil genus name Ampelocissites was established in 1929 has been reexamined with the aid of X-ray micro-computed tomography (μ-CT) scanning and compared with seeds of extant taxa to assess the relationships of these fossils within the grape family, Vitaceae. The specimens were collected from a sandstone of late Paleocene or early Eocene age. Although originally inferred by Berry to be intermediate in morphology between Ampelocissus and Vitis, the newly revealed details of seed morphology indicate that these seeds represent instead the Ampelopsis clade. Digital cross sections show that the seed coat maintains its thickness over the external surfaces, but diminishes quickly in the ventral infolds. This feature, along with the elliptical chalaza and lack of an apical groove, indicate that Ampelocissites lytlensis Berry probably represents Ampelopsis or Nekemias (rather than Ampelocissus or Vitis) and that the generic name Ampelocissites may be useful for fossil seeds with morphology consistent with the Ampelopsis clade that lack sufficient characters to specify placement within one of these extant genera.

First report of the Eocene bivalve Schedocardia (Mollusca, Cardiidae) from Cuba

Herein we provide the first report of the cardiid bivalve Schedocardia from Cuba. The single, partial, valve external mold was derived from the Madruga Formation which is characterized by a richly diverse marine fauna including echinoderms, brachiopods, benthic and planktonic foraminiferans, but from which bivalves were not previously reported. The unit is considered late Paleocene in age (Thanetian), but the presence of Schedocardia supports a possible age extension of the formation into the early Eocene (Ypresian). Moreover, we provide a reconsideration of the historical factors that affected the accepted type locality of the outcrop, which allows for an alternative interpretation of the fauna found therein.

A morphological study of vertebral centra in extant species of pike, Esox (Teleostei: Esociformes)

Isolated centra of members of the Esocidae occur frequently in vertebrate microfossil localities of Late Cretaceous and early Paleocene age and are an important source of data on the early history of the family. However, morphological variation along the vertebral column can lead to incorrect interpretations of diversity if they are not recognized. To facilitate the use of centra for interpreting the diversity and distribution of esocids in Cretaceous vertebrate microfossil localities, the variation along the column in five extant species of esocids is described. Comparison with Cretaceous centra referred to the Esocidae allows identification of a series of features in which species of Esox differ from basal members of the family. These include the presence of a mid-ventral groove bordered by a pair of low budges on centra in the anterior end of the column, and antero-lateral processes on the posterior abdominal and anterior caudal centra. These differences provide a basis for recognizing early occurrences of the genus Esox in the fossil record and thus will allow centra to be used to document the timing of origin of the genus.

Northern Cedar Mountains Red Beds, Tooele County

Recent mapping for the Tooele 30' x 60' quadrangle geologic map revealed more information about interesting exposures of red beds cropping out in an 11-mile (18-km) swath along the northwestern flank of the Cedar Mountains (Clark and others, 2017, 2019 in review). They are unusual because such rocks are seldom preserved in northwestern Utah, an area known for thick thrust sheets of Paleozoic marine carbonate and sandstone. These rocks were first mapped by Robert Maurer for his Ph.D. dissertation on the geology of the Cedar Mountains (Maurer, 1970). He called them North Horn (?) Formation and noted the presence of fresh-water snails (Gyraulus sp.) that a paleontologist said were probably of late Paleocene or Eocene age. The North Horn Formation is considered Late Cretaceous (Maastrichtian age) to Paleocene or Eocene (~70 to 60 Ma) in age. However, recent detrital zircon analysis from sandstone in the unit suggest a much older age, with the youngest grains (maximum depositional age) of 117 Ma, or Early Cretaceous, Aptian (UGS and O’Sullivan, 2017). Two samples of gray mudstone taken for fossil pollen in the unit did not produce any usable material. Inspection of these rocks by Don DeBlieux (Utah Geological Survey paleontologist) revealed no bone or other biological material at this location.

Biostratigraphy of upper Cretaceous through Paleocene successions in Grombalia, Tunisia (southern Tethyan domain)—reworking processes and interpretations

Revision of Late Cretaceous through Paleocene planktic foraminiferal zonal schemes for northeastern Tunisia (Khanguet El Hajjej and Sidi Rhilaine section) has provided new insights into the biostratigraphic framework of the Abiod Formation. A late Paleocene age is endowed with this unit based on the occurrence of late Cretaceous reworked microfauna associated with Morozovella velascoensis planktic foraminifera. The biostratigraphic equivalent, between the mayaroensis and velascoensis Zones near J. Barka, includes an occasional submarine reworking of sediments induced by mass flow transport, indicated by the presence of microfaunal content and heterogeneous extraclasts. The internal organization of sediment (olistoliths, mass flow deposits) reflects tectonic activity and clear evidence of redeposition during the late Paleocene.

Paleocene echinoid faunas of the eastern United States

AbstractTwenty-one species of echinoid are reported from Paleocene rocks of the eastern United States along the outcrop belt from Texas to New Jersey. Six of these are strictly early Paleocene age (Danian), nine strictly late Paleocene age (Thanetian), five range throughout the Paleocene, and one previously reported Paleocene species (Diplodetus moscovensis) is most likely a Cretaceous species. Two new species are described,Salenia palmyran. sp., from the Danian Clayton Formation in Alabama and Georgia, andOva rancocan. sp., from the Thanetian Vincentown Formation in New Jersey. One new species from the Clayton Formation in Mississippi,Arbaciella? sp., is left in open nomenclature.

The age of the Takatika Grit, Chatham Islands, New Zealand

Hollis, C.J, Stickley, C.E., Bijl, P.K., Schiøler, P., Clowes, C.D., Li, X, Campbell, H. March 2017. The age of the Takatika Grit, Chatham Islands, New Zealand. Alcheringa 41, xxx–xxx. ISSN 0311-5518.The oldest Paleogene strata on Chatham Islands, east of New Zealand, are the phosphatized conglomerates and sandstones of the Takatika Grit that crops out on the northeastern coast at Tioriori and unconformably overlies the Chatham Schist. An intact Cretaceous–Paleogene boundary transition is not preserved at this locality. New biostratigraphic analysis of dinoflagellate, diatom and radiolarian microfossil assemblages confirms that the Takatika Grit is of late early–middle Paleocene (New Zealand Teurian stage) age but contains reworked microfossils of early Campanian (Early Haumurian) age. Vertebrate fossils found in this unit are inferred to be a mixture of reworked Cretaceous and in situ Paleocene bones and teeth. The overlying Tutuiri Greensand is of middle–late Paleocene age in its lower part and also contains reworked Cretaceous microfossils.Christopher J. Hollis [c.hollis@gns.cri.nz], Chris Clowes [c.clowes@gns.cri.nz], Xun Li [x.li@gns.cri.nz], Hamish Campbell [h.campbell@gns.cri.nz], GNS Science, PO Box 30-368, Lower Hutt 5040, New Zealand; Catherine Stickley, Evolution Applied Limited, 50 Mitchell Way, Upper Rissington, Cheltenham GL54 2PL, UK [catherine.stickley@gmail.com]; Peter Bijl [p.k.bijl@uu.nl], Marine Palynology and Paleoceanography, Department of Earth Sciences, Utrecht University, 3584 CS Utrecht, the Netherlands; Poul Schiøler [poul.schioler@mgpalaeo.com.au], Morgan Goodall Palaeo, Unit 1/5 Arvida St, Malaga, WA 6090, Australia.

Problems of Paleogene–Neogene stratigraphy of the Zerkal’naya depression, East Sikhote Alin

The Paleogene–Neogene stratigraphic scale of the Zerkal’naya River basin is modified with account for new isotopic and paleobotanical data. It is established that the Tadushi Formation and underlying volcanics, which were previously considered as representing transitional Cretaceous–Paleocene strata, are separated in the section of the Ustinovka quarry by a significant stratigraphic hiatus. According to the new data, the volcanics and the Tadushi Formation are established as Campanian and Late Paleocene in age, respectively. The Bogopol Formation in the type section is dated back to the Middle–Late Paleocene. The Svetlyi Formation is now considered to be Early Eocene in age, rather than Late Eocene–Oligocene as previously thought. A new variant of the stratigraphic scale is proposed for the Paleogene–Neogene deposits of the Zerkal’naya depression.

Paleocene–Eocene transition at Naqb Assiut, Kharga Oasis, Western Desert, Egypt: Stratigraphical and paleoenvironmental inferences

This work depends on the study of the lower part of the Esna Formation which encompasses the Paleocene–Eocene (P-E) transition in Egypt as well as at Naqb Assiut section, Kharga Oasis, Western Desert. The Paleocene/Eocene (P/E) boundary is represented by El Dababiya Quarry Member which consists of five distinctive beds (nos. 1–5) at the GSSP. On the other hand, at Naqb Assiut section this boundary is only represented by the upper two beds (nos. 4&5), whereas, the lower three beds (nos. 1–3) are missing due to a hiatus. This hiatus is marked by the occurrence of an irregular surface contains pebbles and phosphatic materials. This hiatus may be related to the echo of Sryian Arc Orogeny at the P/E time. Biostratigraphically; four planktonic foraminiferal zones are defined from base to top as: Acarinina soldadoensis/Globanomalina pseudomenardii and Morozovella velascoensis (late Paleocene), Acarinina sibaiyaensis and Pseudohastigerina wilcoxensis/Morozovella velascoensis (early Eocene). The Acarinina sibaiyaensis Zone which represents the P//E/boundary is characterized by the occurrence of intrazonal hiatus at it's lower part. The benthonic foraminiferal taxa contain abundant representatives of Midway-type fauna (∼91% of the whole assemblages), beside few Velasco-type faunal ones (∼9%), indicating an outer neritic (150–200 m) water depth of deposition during the P–E transition. Quantitative analysis and composition of benthonic foraminiferal assemblages are indicative for various environmental changes around the P/E boundary. They reflected a high diversity, increase of epifaunal taxa, and low-intermediate productivity conditions, which indicates a well-ventilated bottom water and oligo - to mesotrophic conditions during the late Paleocene age. Rapid extinction of about 18% of the entire benthonic foraminiferal species started at the P/E boundary, where the last occurrence of Angulogavelinella avnimelechi is pronounced at the base of this boundary. There is a decline in the preceding faunal characteristics of the late Paleocene and signified an increase in the abundance of agglutinated and buliminid species. These characters are revealed some environmental stressful conditions of low oxygen and increased productivity. During the early Eocene, the environmental conditions are improved leading to the recovery of most benthonic and planktonic foraminifera.

A burrowing frog from the late Paleocene of Mongolia uncovers a deep history of spadefoot toads (Pelobatoidea) in East Asia.

Fossils are indispensible in understanding the evolutionary origins of the modern fauna. Crown-group spadefoot toads (Anura: Pelobatoidea) are the best-known fossorial frog clade to inhabit arid environments, with species utilizing a characteristic bony spade on their foot for burrowing. Endemic to the Northern Hemisphere, they are distributed across the Holarctic except East Asia. Here we report a rare fossil of a crown-group spadefoot toad from the late Paleocene of Mongolia. The phylogenetic analysis using both morphological and molecular information recovered this Asian fossil inside the modern North American pelobatoid clade Scaphiopodidae. The presence of a spade and the phylogenetic position of the new fossil frog strongly support its burrowing behavior. The late Paleocene age and other information suggestive of a mild climate cast doubt on the conventional assertion that burrowing evolved as an adaptation to aridity in spadefoot toads. Temporally and geographically, the new fossil provides the earliest record of Scaphiopodidae worldwide, and the only member of the group in Asia. Quantitative biogeographic analysis suggests that Scaphiopodidae, despite originating in North America, dispersed into East Asia via Beringia in the Early Cenozoic. The absence of spadefoot toads in East Asia today is a result of extinction.

First timetree of Sphyraenidae (Percomorpha) reveals a Middle Eocene crown age and an Oligo–Miocene radiation of barracudas

The 27 extant species of the family Sphyraenidae represent one of the major groups of piscivorous teleost fishes in tropical and subtropical marine waters. In spite of their ecological importance, currently, no phylogenetic hypothesis is available for this group, and we do not know the tempo of evolution of this clade. In this study, we used a supermatrix approach to assemble a dataset of three mitochondrial loci for 20 sphyraenid species, and time-calibrated this new phylogeny. Our study supports the existence of three main groups of barracudas, which we labelled the “S. barracuda” group, the “S. obtusata” group and the “S. sphyraena” group. The timetree indicates a Late Paleocene age (~57 Ma) for the origin of the groups, and a Middle Eocene (~45 Ma) timing for the beginning of the radiation of extant lineages. Most extant species appear to belong to phylogenetic lineages dating to the Miocene (~5 to 23 Ma). Our study reveals multiple shifts between coral reef-associated and non-reef (usually more pelagic) habitats, as well as two independent origins of large body size within this group.

The Arkot Dağ Mélange in Araç area, central Turkey: Evidence of its origin within the geodynamic evolution of the Intra-Pontide suture zone

In northern Turkey, the Intra-Pontide suture zone is represented by an east–west trending belt of deformed and/or metamorphic units located at the boundary between the Istanbul–Zonguldak terrane to the north and the Sakarya terrane to the south. These units can be regarded as issued from the Intra-Pontide domain, whose geodynamic history is still a matter of debate. Along the Akpinar–Araç–Bayramoren geotraverse, located in central Turkey, an ophiolite-bearing mélange known as the Arkot Dağ Mélange, is well-exposed along the Intra-Pontide suture zone. The Arkot Dağ Mélange plays a key role in the interpretation of the geodynamic history of the Intra-Pontide domain and can be described as a Late Santonian chaotic sedimentary deposit consisting of an up to 1000-m-thick succession of slide-blocks of different sizes and lithologies enclosed in a sedimentary matrix consisting of shales, coarse-grained arenites, pebbly mudstones and pebbly sandstones. The slide-blocks, from a few meters to hectometers in size, are represented by metamorphic rocks (mainly micaschists and gneisses), by ophiolites (peridotites, gabbros, IAT and BABB basalts and cherts) and by sedimentary rocks (cherts, neritic and pelagic limestone, marly limestone and ophiolite-bearing turbidites). The youngest age among the slide-blocks has been provided by the ophiolite-bearing turbidites where a late Coniacian nannofossil assemblage has been found. The cherts have provided a wide range of ages from the Middle Triassic to Late Cretaceous, whereas the fossils found in the limestone indicate Late Jurassic to Early Cretaceous ages. The matrix of the Arkot Dağ Mélange, even if unaffected by metamorphism, shows deformations represented by multiple meters-thick cataclastic shear zones at the boundaries of the mélange slices or inside of them. According to its features, the source area of the Arkot Dağ Mélange was most likely a continental and oceanic thrust sheet emplaced in the Late Cretaceous onto a continental margin. The data collected from the different slide-blocks suggest that the Intra-Pontide domain was characterised by an oceanic basin opened at the latest in the Early Jurassic. The opening of the Intra-Pontide oceanic basin was followed by the development of a subduction zone with a subsequent opening of suprasubduction oceanic basin in the Middle Jurassic–Early Cretaceous. The convergence in this suprasubduction oceanic basin started at the Early/Late Cretaceous boundary by an obduction process, whereas its final closure can be regarded as Late Paleocene in age.

First Clarkforkian Equivalent Land Mammal Age in the Latest Paleocene Basal Sparnacian Facies of Europe: Fauna, Flora, Paleoenvironment and (Bio)stratigraphy

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a “miacid” carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America.

Paleobotany and paleoecology of Gao Mine, a late Paleocene fossil locality near Red Deer, Alberta, Canada

In addition to having a rich assemblage of mammalian fossils, the Gao Mine locality in the Paskapoo Formation of south-central Alberta has yielded numerous plant specimens of late Paleocene (late Tiffanian or Ti5) age. The plant fossils are preserved in siltstones and fine-grained sandstones interpreted as overbank sediments that were deposited on an aggrading floodplain. The assemblage is dominated by the cupressaceous conifer Metasequoia foxii and the cercidiphyllaceous dicot Joffrea speirsiae, including their well-preserved seedlings. The flora also contains foliage of the ferns Onoclea and Speirseopteris and the woody dicots Palaeocarpinus, Aphananthe/Celtis, Aesculus, Beringiaphyllum, ?Trochodendron, and Wardiaphyllum, as well as seedlings of unknown dicotyledonous angiosperms. Metasequoia foxii and Speirseopteris are unique to the floras of Gao Mine and the nearby Munce’s Hill site (Tiffanian Ti4). The remainder of the taxa are common in late Paleocene floras of North Dakota, Montana, and Wyoming, all USA. The floras of the nearby Joffre Bridge Roadcut and Blindman River sites (both Tiffanian Ti3) are more diverse, but both of those sites encompass a wider range of depositional environments and may include higher percentages of allochthonous material. Most of the Gao Mine material is autochthonous. The seedlings were buried in place, along with the surrounding leaf litter, preserving a record of the local plant community.

Acerca de la presencia de rocas del Paleoceno Superior en la sucesion de antepais de Cabo Nariz, Tierra del Fuego, Chile: geologia y nuevos datos palinologicos y de U-Pb.

En la costa occidental de Tierra del Fuego, al sur de Cabo Nariz, Chile, afloran sucesiones sedimentarias de antepais cretacicas tardias a paleocenas de la cuenca de Magallanes. Tanto su contenido de dinoquistes como las edades de circones detriticos indican que comprenden un intervalo de edades entre el Campaniano tardio y el Thanetiano (Paleoceno Tardio). La base de la sucesion sedimentaria expuesta comprende limolitas de facies de plataforma externa (Formacion Cerro Cuchilla), la cual cubre tectonicamente los estratos de Cabo Nariz. Estos ultimos se dividen en dos miembros: uno inferior de facies turbiditicas con predominio de limolitas y un miembro superior tambien de facies turbiditicas, pero con predominio de areniscas y facies de canales ricos en areniscas y conglomerados. De acuerdo a la presencia de dinoquistes, la Formacion Cerro Cuchilla tiene edades comprendidas entre el Campaniano tardio y el Daniano temprano. El contenido fosilifero de los estratos de Cabo Nariz, indica una edad deposicional selandiana (Paleoceno Medio), la cual concuerda con las edades maximas posibles de sedimentacion dadas por las edades de circones detriticos, que es campaniana (76,5±0,7 Ma), y muy cerca del Thanetiano (Paleoceno Tardio) (57,6±1 Ma) para los miembros inferior y superior respectivamente. Las sucesiones sedimentarias de los estratos de Cabo Nariz son interpretadas como un sistema de abanico submarino que prograda hacia el norte-noroeste entre el Paleoceno Medio y Tardio. Este es considerado como un deposito de detritos proveniente desde un orogeno que se alzo al sur durante ese periodo. El intervalo de edades de los circones detriticos sugiere que hubo un periodo de baja intensidad de actividad magmatica en el area fuente, en torno al limite K-T.