Late Eocene Age Research Articles

Foraminifera from the Tepetate Formation (Heim) at Las Pocitas, Baja California Sur, Mexico

In order to constrain the age and depositional paleoenvironment of the Tepetate Formation, benthic and planktonic foraminifera were analyzed in samples recovered from an exploration well located at Las Pocitas, Baja California Sur, Mexico. The planktonic taxa identified allowed recognition of Zone P9 (Planorotalites palmerae-Acarinina pentacamerata), equivalent to a late early Eocene age of 50.4–49 Ma. The benthic foraminiferal association suggests that the sediments were deposited in a continental slope environment at an upper bathyal water depth of ca. 500 m. Composition and diversity of planktonic foraminifera indicate the presence of warm-temperate surface water masses. Micropaleontological evidence presented here and from previous reports indicates that the samples studied represent only a portion of the Tepetate Formation.

Geology of the Cove Mine, Lander County, Nevada, and a Genetic Model for the McCoy-Cove Hydrothermal System

The McCoy Au-Ag skarn and Cove Au-Ag deposits are located in the northern Fish Creek Mountains, Lander County, Nevada. Through the end of mining in 2001, large-scale open-pit and associated underground production at the two deposits yielded 3.3 million ounces (Moz) of Au and 108 Moz of Ag. Most production was from Cove, making it the fourth-largest Ag producer in the history of Nevada. Cove is hosted by the middle to early Late Triassic Augusta Mountain Formation, which consists of limestone with lesser dolostone and clastic units. Ore also is present locally in Eocene porphyritic granodiorite dikes and sills. The deposit comprises two distinct ore types: a central core of polymetallic vein-type ore and an outer aureole of relatively Ag rich Carlin-style ore. Polymetallic veins consist of pyrite-sphalerite-galena–dominated Au- and Ag-bearing veins, veinlets, stockworks, crustifications, and disseminations in clastic and carbonate strata and locally in the intrusions. Carlin-style ore comprises disseminated Fe ± As sulfides with arsenian, argentiferous, and auriferous components ± native Au-electrum in silty to sandy carbonate strata. Polymetallic vein-type ore has Ag/Au ratios of >50/1, and Carlin-style ore has Ag/Au ratios that decrease from ~50/1 near the feeder faults to ~1/1 in one of the more distal ore zones. Both types of ore are associated with decarbonatized, silicified, and illitized rocks. New structural and age data for fresh and altered intrusive rocks indicate that mineralization at Cove occurred during active extension and magmatism at ~39 Ma (40Ar-39Ar). Fluid inclusion and δD and δ18O data for polymetallic vein-type ore indicate that the mineralizing fluids had temperatures of 250° to 370°C and were magmatic in origin. Cove is located 1.6 km northeast of McCoy, where Early Tertiary igneous activity occurred in two pulses. The first pulse consisted of relatively oxidized magnetite-series magma and formed the central stock at McCoy and related dikes that extend to the Cove deposit. This pulse occurred at ~41.5 Ma and produced subeconomic skarn at McCoy. The second pulse consisted of relatively reduced ilmenite-series magma and produced economic skarn ore at McCoy. Adularia from a mineralized skarn assemblage at McCoy was dated at ~39 Ma (K-Ar). The age data indicate that McCoy and Cove formed contemporaneously. The δ34S data for ore-stage sulfides from skarn ore at McCoy, and polymetallic vein-type and Carlin-style ore at Cove indicate a common source for S for the three types of ore. This source is interpreted to have been the pulse of ilmenite-series magma. Although the volume of the Carlin-style ore at Cove is substantially larger than that of the polymetallic vein-type ore, the relatively high concentrations of base metals and clear associations with igneous activity have made Cove difficult to classify. The new data indicate that Cove is a telescoped system consisting of polymetallic vein-type and porphyry-related, distal disseminated ores. The zonation for the McCoy-Cove system is nearly identical to zonations described by other workers for Au-enriched porphyry systems. In this case, the porphyry center and skarn ore at McCoy comprise the proximal component, and polymetallic vein-type and Carlin-style ores at Cove are the intermediate and distal components, respectively. Economic concentrations of Au occur in all three zones, which are separated from one another by subeconomic concentrations of Au. The Carlin-style orebodies at Cove share several important similarities with ores in classic Carlin-type deposits, including ore characteristics, associated alteration styles, and host lithologic units. The late Eocene age of the McCoy-Cove system is also a typical age for Carlin-type deposits in the Great Basin. The proposed genetic model for McCoy-Cove may have important implications for the exploration potential of intrusion-related and Carlin-type deposits worldwide.

Evolutionary transformations of hystricognath Rodentia and the climatic change in the Eocene to Late Oligocene time interval

The Eocene-Oligocene transition interval is characterized by global cooling and the development of large Antarctic ice sheets, in response to global cooling, the Paleogene vegetation shifted from dominantly tropical/subtropical Eocene forests to more “mixed mesophytic forests” and floras adapted to (seasonal) dry conditions during the Oligocene. Fully established grass-dominated environments, i.e. grasslands, developed not until the Miocene. The oldest fossils of Hystricognathi (Rodentia) are of Late Eocene age and the group was already diverse in the Late Oligocene. In South America seven distinct higher taxa are recorded for the Late Oligocene, followed by a subsequent radiation during the Miocene. According to a reconstruction based on morphology of Recent taxa and paleontological data, the last common ancestor of Recent (crown group) Hystricognathi possessed tooth structures, mouth cavity organisation and a nasal apparatus suggesting a mainly herbivorous diet with a wide range of nutritional resources. This pattern most probably evolved before the Late Eocene. The fossil record shows that further evolutionary transformations within Hystricognathi, i.e. the development of high crowned (hypsodont) cheek teeth, occurred from the Oligocene onward. They made possible a more pronounced use of plants with high fibre content, such as grasses. The reconstructed stem species pattern (ancestral character set) of Hystricognathi is characterised by a less energy consuming mode of reproduction which is hypothesised to be a prerequisite to herbivory with pronounced utilisation of grasses. When more open ecosystems originated in the Oligocene, several lineages of Hystricognathi show adaptations to the utilisation of plant material including grasses. However, these features were present long before the establishment of widespread grasslands during the Miocene when particularly the South American Hystricognathi experienced a second major phase of radiation. Most likely, the early evolution of Hystricognathi from the Oligocene onward occurred primarily in parallel to the development of more temperate forest communities and more open ecosystems, e.g. woodlands, wooded savannah communities, and shrubland.

OLIGOCENE ECHINOIDS FROM WADI AL GHADAF, JORDAN

A small collection of echinoids from the Eastern Desert of Jordan includes the species Clypeaster biarritzensis , Amphiope ? sp., Echinolampas cherichirensis , and Eupatagus meslei . This fauna closely resembles faunas of early Oligocene age from North Africa. The presence of the associated foraminifera Nummulites intermedius and N. fichteli dates the upper portion of the Wadi Shallala Formation exposed in the area of Wadi Al Ghadaf as early Oligocene (Rupelian), younger than the generally accepted middle (Bartonian) to late Eocene (Priabonian) age of this formation. The presence of rocks of this age in Jordan along what was probably the southern margin of the Tethyan Seaway is evidence that communication between the eastern and western provinces of the Western Tethys Region still existed in this area at this time.

Early tholeiitic and calc-alkaline arc magmatism of middle to Late Eocene Age in the southern Ogasawara (Bonin) forearc

Early tholeiitic and calc-alkaline arc magmatism of middle to Late Eocene Age in the southern Ogasawara (Bonin) forearc

Miocene whale-fall from California demonstrates that cetacean size did not determine the evolution of modern whale-fall communities.

Whale-fall communities support a deep-sea invertebrate assemblage that subsists entirely on the decaying carcasses of large cetaceans. The oldest whale-falls are Late Eocene in age, but these early whale-falls differ in faunal content and host cetacean size from Neogene and Recent whale-falls. Vesicomyid bivalves, for example, are major components of the sulphophilic stage in Miocene and Recent whale-fall communities, but they are absent from Palaeogene fossil whale-falls. The differences between Palaeogene and Neogene communities led to the hypothesis that the origin of modern whale-fall communities was linked with the evolution of extremely large mysticetes, which provided sufficient biomass and oil to sustain the modern complement of whale-fall invertebrates. Here, we describe a fossil whale-fall community from the Miocene of California, showing vesicomyid bivalves in direct association with a host mysticete smaller than the adult individuals of any living mysticete species. This association, which is the youngest yet reported from the Neogene of North America, demonstrates that body size is not a necessary factor for the formation of modern whale-fall communities. Instead, we suggest that high skeletal oil content may have been a more important factor, which, based on the age of the fossil whale-fall, evolved at least by the Late Miocene.

Cenozoic stratigraphy and sedimentation history of the northern Philippine Sea based on multichannel seismic reflection data

Abstract To clarify the regional distribution and characteristics of the sedimentary deposits in the northern part of the Philippine Sea, multichannel seismic reflection surveys of 26 864 km in total length were performed. The seismic reflection data were interpreted and correlated with available Deep Sea Drilling Project/Ocean Drilling Program (DSDP/ODP) data and a general stratigraphic framework of the area was established. The sedimentary deposits in this area were divided into five layers; Units I, II, III, IV and V in ascending order. Their approximate geological ages are the Early Eocene, Middle to Late Eocene, Oligocene, Miocene and Pliocene‐Pleistocene, respectively. Seismic records were classified into three seismic facies, Facies A, B and C, on the basis of their characteristics. They were judged to represent pelagic and hemipelagic sediments of non‐volcanic origin, fine pyroclastic sediments and coarse pyroclastic or volcanic sediments, respectively, by comparing them with lithological data in the DSDP/ODP holes. From the thickness and facies distributions of these sediments, a sedimentary history in the area was reconstructed as follows. The oldest sediments in the study area, Unit I, interfinger with some parts of the Daito Ridge (acoustic basement) in the Minami Daito Basin. The geological age of the unit is estimated by microfossils in the sediment and supports the idea that this part of the Daito Ridge is composed of the Early Eocene oceanic basalt. Later, a fair amount of sediments were deposited in the Minami Daito Basin in the Middle to Late Eocene age. A large volume of volcanic materials was supplied from the Paleo‐Kyushu‐Palau Ridge in the Kita Daito Basin in the Eocene and Oligocene ages. The eastern part of the Shikoku and Parece Vela basins is characterized by volcanic sediments supplied from the Nishi Shichito and West Mariana Ridges in the Miocene age. However, pelagic and hemipelagic sediments prevail in the northern part of the Shikoku Basin in the Miocene or later. In short, the area of principal sedimentation has generally shifted from west to east through geological time, reflecting the evolution of the island arc systems with the same trend in the northern Philippine Sea.

Sequence stratigraphy of Eocene incised valley clastics and associated sediments, Island of Rab, northern Adriatic Sea, Croatia

Clastic sediments of Middle–Late Eocene age were studied on the Island of Rab (northern Adriatic Sea, Croatia) in order to reconstruct their depositional history, depositional environments, and geometry of sandstone bodies. Detailed outcrop logging and mapping revealed the response of depositional systems to frequent relative sea-level changes, which initiated significant basinward and landward shifts of facies, respectively. Tidal sandstones are commonly underlain by shoreface sandstones, and overlain by offshore sandy marls, whereas the latter are again overlain by shoreface sandstones. Major relative sea-level falls initiated basinward shift of depositional systems and the incision of incised valleys or estuaries, and consequently truncated the underlying shelf sediments. In some cases, the accelerated sea-level fall caused rapid shoreface progradation which is interpreted as a forced regression. Relative sea-level rise caused flooding of the incised relief, and deposition of tidal sandstone bodies which overlie type-I sequence boundaries. The coarse lag sediment of these sequence boundaries locally disappears laterally, and the boundary is granulometrically less prominent. All of the major bounding surfaces have been recognized in the sections studied, although the maximum flooding surface is recognized as a thin “zone” instead of a single surface. Altogether, 28 complete sequences, and 15 parasequences are recognized in the informal unit of the Lopar sandstones, documenting the depositional response to high-frequency relative sea-level oscillations. They have so far not been recognized in the Eocene of the eastern Adriatic region.

Miocene shallow-water limestones from São Nicolau (Cabo Verde): Caribbean-type benthic fauna and time constraints for volcanism

Shallow-water limestones of presumed Late Cretaceous and Eocene age, interbedded with basaltic lavas, were described by earlier authors from São Nicolau in the northwestern part of the Cabo Verde archipelago. If confirmed, these ages would imply late Mesozoic shallow-marine and subaerial volcanic activity in the Cabo Verde archipelago, and document a geological history very different from that known so far from other Cabo Verde Islands, from which no subaerial volcanic activity before the mid-Cenozoic is known. Our re-investigation of the foraminiferal fauna indicates a Late Miocene age for the presumed Late Cretaceous and Eocene limestones. The hypothesis of a long-lived hot spot, active by the Early Cretaceous, and of a major island-building stage in the Cabo Verde Islands during this period, is therefore not supported by the present bio- or chronostratigraphic data.

A new species of Thaumastosaurus (Amphibia: Anura) from the Eocene of Europe

ABSTRACT Thaumastosaurus gezei, sp. nov., is described based on the incomplete, holotype skull and an isolated, referred squamosal, both from the so-called “old collections” (late middle or late Eocene in age) from the Phosphorites du Quercy, France. A suite of cranial features, mainly involving sculpture patterns and details of the maxilla and squamosal, differentiates T. gezei from the other three species of Thaumastosaurus. T. gezei appears to be unique among known species of Thaumastosaurus and is unusual among other anurans in having an anteriorly elongate process of the squamosal that extends along the entire dorsal edge of the maxilla, thereby preventing the maxilla from contacting the nasal and contributing to the orbital margin. This derived squamosal configuration, and some other cranial features, suggest a possible relationship between Thaumastosaurus and the South American ceratophryids. If such a relationship proves correct, Thaumastosaurus would be one of the few vertebrate taxa from the Eocene of Europe with South American affinities.

Geologie der Iberger Klippen und ihrer Flysch-Unterlage

Geologie der Iberger Klippen und ihrer Flysch-Unterlage

Lithofacies and fluvial–lacustrine environments of the Palaeogene Sevkhuul and Ergil members (Ergiliin Zoo Formation, South Gobi, Mongolia)

The clastic sequence of the Ergiliin Zoo Formation stretches along the Mongolian–Chinese border in the southern Gobi Desert, Mongolia. Its members (Sevkhuul, Ergil) exposed in the Erdene Sum region are well known for their vertebrate remains of Late Eocene and Oligocene age. Based upon field work, the continental red beds were subdivided into four units described as (I) prodelta/mud-sand flat, (II) delta front, (III) delta plain and (IV) calcretes. All sub-environments are in a fluvial–lacustrine setting. Electronmicroprobe analysis, in addition to conventional thin-section examination, was applied to shed some light on the complex mineral association made up of light minerals (quartz, plagioclase, ternary feldspar, orthoclase, smectite, illite, rare palygorskite), heavy minerals (almandine–pyrope solid solution series, zoisite–epidote s.s.s.) and abundant goethite and carbonate minerals (calcite, dolomite). Igneous rocks being exposed in the source area have contributed to the formation of carbonate minerals and Mg-bearing sheet silicates during diagenesis. Higher up on the delta plain transitional between distal alluvial and deltaic deposits, fluids emerged from the distal alluvial–fluvial deposits and formed calcareous duricrusts. Drawing conclusions from the rock colour, the mineral assemblage and the palaeoecological data, the climatic conditions may be described as alternating wet and dry seasons, closely resembling those conditions of a modern savannah.

A NEW SPECIES OF MOERITHERIUM (PROBOSCIDEA, MAMMALIA) FROM THE EOCENE OF ALGERIA: NEW PERSPECTIVES ON THE ANCESTRAL MORPHOTYPE OF THE GENUS

Abstract: A new species of Moeritherium (Proboscidea, Mammalia), M. chehbeurameuri sp. nov., is described from remains discovered in the early late Eocene locality of Bir El Ater, Algeria. Although mainly represented by isolated teeth, it shows distinct synapomorphies which justify its attribution to the genus Moeritherium, together with exclusive features that led to the creation of the new species. The main characteristic of this new taxon is the almost complete lophodonty shown by its molars, while Moeritherium is commonly regarded as a bunolophodont to bunodont taxon. In addition to this lophodonty, this new taxon shows anatomical features as yet unknown for the genus, but often met within lophodont early proboscidean taxa such as Phosphatherium escuilliei and Numidotherium koholense. Although a revision of the whole genus Moeritherium is outside the scope of this paper, the main controversies and discussion about the definition of species within the genus Moeritherium are discussed. The surprising lophodonty of M. chehbeurameuri, together with its small size, its early late Eocene age and the weak molarization of its P3 support the hypothesis of a lophodont hypothetical ancestor for moeritheres, and therefore strengthen the growing hypothesis of a lophodont dental ancestral morphotype for proboscideans.

Geochemical characteristics of the composite Kaçkar batholith generated in a Neo-Tethyan convergence system, Eastern Pontides, Turkey

The composite Kaçkar batholith, of Cretaceous to Late Eocene age, consists of various intrusions derived from different geodynamic settings ranging from early to mature arc, through collision, to post-collisional extension in the Neo-Tethyan convergence system of the eastern Pontides of NE Turkey. The intrusions were emplaced into Cretaceous and Middle Eocene volcano-sedimentary units, and are unconformably overlain by Late Cretaceous, Early to Middle Eocene and Miocene units. The 10 lithological units are grouped into five geodynamic associations on the basis of geological setting and geochemical characteristics: (1) early arc origin as represented by the medium-K calc-alkaline (CALK) Çamlıkaya granitoid of Early Cretaceous age, (2) mature arc origin as represented by the medium- to high-K calc-alkaline Sırtyayla and Marselevat granitoids of Late Cretaceous to Early Palaeocene age, (3) syn-collisional plutonism as represented by the peraluminous Asniyor leucogranite of Palaeocene age, (4) post-collisional plutonism as represented by the high-K calc-alkaline Ayder K-feldspar megacrystic granitoid and the Sasmistal microgranite of Middle to Late Eocene age, (5) the extension-related, mildly alkaline Güllübağ monzonite, the medium-K calc-alkaline to slightly tholeiitic (THOL) Halkalıtaş quartz diorite, and the low-K tholeiitic Ardeşen gabbro and İsina diabase of Late Eocene age that are mainly exposed as small, shallow stocks and N–S, NE–SW, NW–SE and E–W trending veins.

Upper Eocene larger foraminifera from the Dammam Formation in the border region of United Arab Emirates and Oman

Research Article| December 01, 2005 Upper Eocene larger foraminifera from the Dammam Formation in the border region of United Arab Emirates and Oman Mohamed Boukhary; Mohamed Boukhary 1Geology Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt email: mboukhary@hotmail.com Search for other works by this author on: GSW Google Scholar Osman Abdelghany; Osman Abdelghany 2Geology Department, Faculty of Science, United Arab Emirates University, Al-Ain, P.O.Box 17551, United Arab Emirates corresponding author email: Osman.abdelghany@uaeu.ac.ae Search for other works by this author on: GSW Google Scholar Salah Bahr; Salah Bahr 1Geology Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt email: mboukhary@hotmail.com Search for other works by this author on: GSW Google Scholar Yasmine Hussein-Kamel Yasmine Hussein-Kamel 1Geology Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt email: mboukhary@hotmail.com Search for other works by this author on: GSW Google Scholar Author and Article Information Mohamed Boukhary 1Geology Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt email: mboukhary@hotmail.com Osman Abdelghany 2Geology Department, Faculty of Science, United Arab Emirates University, Al-Ain, P.O.Box 17551, United Arab Emirates corresponding author email: Osman.abdelghany@uaeu.ac.ae Salah Bahr 1Geology Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt email: mboukhary@hotmail.com Yasmine Hussein-Kamel 1Geology Department, Faculty of Science, Ain Shams University, Abbassia 11566, Cairo, Egypt email: mboukhary@hotmail.com Publisher: Micropaleontology Press First Online: 09 Mar 2017 Online ISSN: 0026-2803 Print ISSN: 1937-2795 © 2005 The Micropaleontology Project, Inc. Micropaleontology (2005) 51 (6): 487–504. https://doi.org/10.2113/gsmicropal.51.6.487 Article history First Online: 09 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 Mohamed Boukhary, Osman Abdelghany, Salah Bahr, Yasmine Hussein-Kamel; Upper Eocene larger foraminifera from the Dammam Formation in the border region of United Arab Emirates and Oman. Micropaleontology 2005;; 51 (6): 487–504. doi: https://doi.org/10.2113/gsmicropal.51.6.487 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 SocietyMicropaleontology Search Advanced Search Abstract An Upper Eocene diagnostic larger foraminiferal assemblage is described and illustrated from carbonates of the uppermost Dammam Formation, on the western side of the Northern Oman Mountains, along the United Arab Emirates and Oman border. This assemblage comprises Fabiania cassis (Oppenheim 1896), Silvestriella tetraedra (Gümbel 1870), Pellatispira madaraszi Hantken 1876, Nummulites fabianii (Prever 1905), N. ptukhiani Kacharava 1969 and N. retiatus (Roveda 1959). The presence of Nummulites ptukhiani and N. fabianii within the same horizon of Pellatispira madaraszi places both species in the Priabonian stage, confirming a Late Eocene age for the uppermost part of the Dammam Formation. The studied carbonates were deposited in an inner shelf environment, which may be related to the eustatic fall of sea level at the end of the Late Eocene. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Tertiary to recent oblique convergence and wrenching of the Central Dinarides: Constraints from a palaeostress study

The late Eocene to Neogene tectonic evolution of the Dinarides is characterised by shortening and orogen-parallel wrenching superposed on the late Cretaceous and Eocene double-vergent orogenic system. The Central Dinarides exposes NW-trending tectonic units, which were transported towards the Adria/Apulian microcontinent during late Cretaceous–Palaeogene times. These units were also affected by subsequent processes of late Palaeogene to Neogene shortening, Neogene extension and subsidence of intramontane sedimentary basins and Pliocene–Quaternary surface uplift and denudation. The intramontane basins likely relate to formation of the Pannonian basin. Major dextral SE-trending strike-slip faults are mostly parallel to boundaries of major tectonic units and suggest dextral orogen-parallel wrenching of the whole Central Dinarides during the Neogene indentation of the Apulian microplate into the Alps and back-arc type extension in the Pannonian basin. These fault systems have been evaluated with the standard palaeostress techniques. We report four palaeostress tensor groups, which are tentatively ordered in a succession from oldest to youngest: (1) Palaeostress tensor group 1 (D 1) of likely late Eocene age indicates E–W shortening accommodated by reverse and strike-slip faults. (2) Palaeostress tensor group 2 (D 2) comprises N/NW-trending dextral and W/WSW-trending sinistral strike-slip faults, as well as WNW-striking reverse faults. These indicate NE–SW contraction and subordinate NW–SE extension related to Oligocene to early Miocene shortening of the Dinaric orogenic wedge. (3) Palaeostress tensor group 3a (D 3a) comprises mainly NW-trending normal faults, which indicate early/middle Miocene NE–SW extension related to syn-rift extension in the Pannonian basin. The subsequent palaeostress tensor group 3b (D 3b) includes NE-trending, SE-dipping normal faults indicating NW–SE extension, which is likely related to further extension in the Pannonian basin. (4) Palaeostress tensor group 4 (D 4) is characterised by mainly NW-trending dextral and NE-trending sinistral strike-slip faults. Together, with some E-trending reverse faults, they indicate roughly N–S shortening and dextral wrenching during late Miocene to Quaternary. This is partly consistent with the present-day kinematics, with motion of the Adriatic microplate constrained by GPS data and earthquake focal mechanisms. The north–north-westward motion and counterclockwise rotation of the Adriatic microplate significantly contribute the shortening and present-day wrenching in the Central Dinarides.

Three new Verrucidae (Crustacea: Cirripedia) from the Upper Eocene of the Euganean Hills (Northeast Italy)

Marls with pillow lavas of Late Eocene age from Castelnuovo in the Euganean Hills (Padua, NE Italy) have yielded three new verrucid cirripede species, Verruca veneta nov. sp., Costatoverruca? seguenzai nov. sp., and Metaverruca euganea nov. sp. The stratigraphic distribution of these taxa is discussed in light of previous verrucid records and their geologic context is established. They represent the oldest known verrucids from Italy.

Relationship between geology and landslide occurrence in the Sor Range, Quetta, Pakistan

The Sor Range is situated about 16 km east of Quetta in the axial zone west of the Sulaiman Thrust- Fold Belt. It contains sedimentary rocks ranging in age from Jurassic to Recent. The Ghazij Formation of Early Eocene is divided into the Lower, Middle, and Upper Members, respectively. The Kirthar Formation of Late Eocene age is divided into the Habib Rahi Limestone and Serki Member. The Siwaliks of Miocene to Pleistocene age consist of the Nagri, Dhok Pathan, and Soan Formation (Urak conglomerate) and are overlying the Kirthar Formation with an unconformity.
 Landslide susceptibility mapping was carried out on a scale of 1:50,000. This study describes various ancient and active landslides in the area and fissures developed in the Ghazij Formation that cover an area of about 130,000 m2. There are also several hundred metres long and very wide fissures in the dip slope of the Kirthar Formation. The widespread instabilities are confined to the fold belts as well as major wrench and thrust faults, and they were triggered or reactivated by earthquakes.

Dolomite Formation in Pelagic Limestone and Diatomite, Romanche Fracture Zone, Equatorial Atlantic

Abstract Two dredge samples from the Romanche Fracture Zone in the equatorial Atlantic document dolomite formation in pelagic sediments in a deep-sea environment. The samples come from a highly deformed sedimentary succession, the Romanche Sedimentary Sequence, constituting the transverse ridge accompanying the transverse valley of the fracture zone to the north. These sediments were folded and uplifted to or near the seafloor prior to the growth of an early Miocene carbonate platform which unconformably overlies them. Dolomitized pelagic limestones of Early Cretaceous age preserve solution molds and unaltered tests of radiolaria (opal-A) and ghosts of calcareous nannoplankton in a dolomicritic groundmass. Carbon isotope data indicate a normal marine source of carbon, and oxygen isotope compositions are consistent with precipitation from cool, marine pore waters at or near the sediment-water interface. The 87/Sr86Sr ratio suggests dolomitization at around 25 Ma, presumably when the sediments were exhumed to or near to the seafloor. In contrast, a dolomite-cemented diatomite of presumably late Eocene age shows no relics of a carbonate precursor. Dolomite crystals grew freely in the originally highly porous rock, cementing it into a tight fabric. The absence of compaction suggests that cementation by dolomite took place soon after deposition and before significant burial of the sediment. Carbon and oxygen isotope compositions of this dolomite suggest that its formation also occurred from cool, marine waters. The 87Sr/86Sr ratio shows the value of seawater around 35 Ma. Under the assumption that dolomite cementation was by seawater, it occurred shortly after deposition at or near the seafloor.

Quantitative analysis and palaeoecology of Eocene Ostracoda and benthonic foraminifera from Gebel Mokattam, Cairo, Egypt

A detailed study of the ostracod and benthonic foraminiferal assemblages of two sections from Gebel Mokattam (east of Cairo) yielded ostracod species and benthonic foraminiferal species in 25 samples from the Mokattam Group of late middle Eocene age and the Maadi Group of late middle to late Eocene ages. The remaining five samples representing the Gebel Ahmar Formation of Oligocene age, at the top of the succession, are barren of fossils. Cluster analysis, using the Jaccard coefficient of similarity (the group average linkage method), helped distinguish four ecozones of late middle to late Eocene age. Principal coordinate analysis (PCO) applied to the same data led to the distinction of two important environmental factors affecting the distribution of these ostracod assemblages in the study area: turbidity currents–exposure to water depth and oxygenation of water. Analyses of the microfacies and microfaunas indicate deposition in a well-oxygenated, turbid, shallow marine environment except at the base of the sequence, which implies reduced oxygenation. Despite the lack of planktonic foraminifera in the studied sections, however, the identified benthonic foraminiferal assemblage affirms that the age of the Mokattam Group is Biarritzian, while that of the Maadi Group ranges from Biarritzian to Priabonian. The Gebel Ahmar Formation, covering the whole succession, is assigned to the Oligocene. A reduced ostracod migration activity was detected along the shores of Tethys during the middle to late Eocene times.