Development of phosphatized hardgrounds in the miocene Globigerina Limestone of the maltese archipelago,including a description ofGamopleura melitensis sp. nov. (Gastropoda,Euthecosomata)

In the Maltese Islands two phosphorite layers occur in the Globigerina Limestone Formation (?Aquitanian to Langhian). These layers, labeled C1 and C2, display a multi-stage development with a two-stage hardground development on top (labelled lower and upper hardground). In the lower hardground, lithification and mineralization followed a sedimentary framework betweenThalassinoides burrows, resembling the Cretaceous ‘nodular chalks’ which were marginally phosphatized when they became exposed to the sea floor. In Phosphorite Layer C2, development of this lower hardground has been superimposed by small-scale cycles. It is underlain by one or more omission surfaces each followed by phosphate-rich, bioturbated biomicrites.     

The development of an Early Ordovician hard ground community in response to rapid sea-floor calcite precipitation

The Kanosh Shale (Upper Arenig, Lower Ordovician) of west-central Utah. USA. contains abundant carbonate hardgrounds and one of the earliest diverse hardground communities. The hardgrounds were formed through a combination of processes including the development of early digenetic nodules in clay sediments which were exhumed and concentrated as lags by storms. These cobble deposits. together with plentiful biogenic metrical. were cemented by inorganically precipitated calcite on the sea floor. forming intraformational conglomerate hardgrounds. Echinoderms may have -played a critical role in the development of hardground faunas since their disarticulated calcite ossicles were rapidly cemented by syntaxial overgrowths. forming additional cobbles and hardgrounds. The echinoderms thus may have taphonomically facilitated the development of some of the hard substrates they required. A significant portion of the hardground cements may have been derived from the early dissolution of aragonitic mollusk shells. Kanosh hardground species include the earliest bryozoans recorded on hardgrounds and large numbers of stemmed echinoderms. primarily rhipidocystid cocrinoids. Bryozoans and echinoderms covered nearly equal areas of the hardground surfaces. and there was a distinct polarization between species which preferred the upper. exposed portions of the hardgrounds and others which were most common on undercut. overhang surfaces. The Kanosh Shale hardground fossils combine elements of Late Cambrian assemblages and Middle Ordovician faunas, thus confirming predicted trends in hardground community evolution. especially the replacement of cocrinoids by bryozoans and. to a lesser extent, by other stemmed echinoderms, especially crinoids. The Kanosh community marks the transition from the Cambrian Fauna to The Paleozoic Fauna in The hardground ecosystem. *Carbonate hardgrounds, aragonite dissolution, calcite cement, Echinodermara, Trepostomata, Nicholsonclla. Dianulites. Porifpra. taphonomic facilitation, Utah. Pogonip Group, Kanosh Shale. Ordovician.     

ECHINOID AND CRUSTACEAN BURROWS AND THEIR DIAGENETIC SIGNIFICANCE IN THE MAASTRICHTIAN-DANIAN OF STEVNS KLINT, DENMARK

The increase in species and specimens of fossils in the uppermost part of the Maastrichtian White Chalk is interpreted as a result of reduced depth. The absence of bryozoans, brachiopods, and regular echinoids in the Cerithium Limestone indicates sedimentation in tidal pools. After sedimentation of the Cerithium Limestone, burrowing activity followed. A burrow of Brissopneustes danicus similar to burrows of the recent Echinocardium cordatum is described. Callianassa and its burrows are found in the Upper Danian calcarenite but not in the Lower Danian or Maastrichtian of Denmark. The dominant type of burrows along the Maastrichtian-Danian boundary has presumably been formed by the crustacean Ctenocheles.
The early post-Maastrichtian burrowing activity was succeeded by (1) induration of the bottom sediment and a slight abrasion (2) dissolution of aragonite shells and siliceous sponges, (3) offshore sedimentation and filling of the burrows with Lower Danian chalk mud, bryozoan fragments and other fossil remains, and (4) settling in the deeper part of the soft chalk sediment and precipitation of flint in or around burrows near the surface of the sediment.     

A new coral‐associated decapod assemblage from the Upper Miocene (Messinian) Upper Coralline Limestone of Malta (Central Mediterranean)

Abstract: A rich coral‐associated decapod assemblage is recorded from the ‘Depiru Beds’ of the upper part of the Upper Coralline Limestone (Messinian, Upper Miocene), from the island of Malta. Nineteen species within 17 genera have been discovered, where 14 genera are new for Malta. Four new species are described, namely Micippa annamariae sp. nov., Pilumnus scaber sp. nov., Panopeus muelleri sp. nov. and Herbstia melitense sp. nov. Herbstia melitense sp. nov. constitutes the first record of the genus from the fossil record in the Mediterranean region. This discovery more than doubles the number of known fossil decapod species from Malta. The fossil bivalve Jouannetia (J.) semicaudata Des Moulins, 1830 and the extant decapod Maja goltziana D’Oliveira, 1888, are also recorded for the first time from Malta. Other Neogene coral‐associated decapod assemblages are investigated and correlated with the new assemblage from Malta. The migration of taxa between the Mediterranean region and the Paratethys, particularly during the Lower Badenian (Langhian), is evidenced by the strong affinity of the Maltese decapod assemblage with that of the Middle Miocene Badenian assemblages from Hungary, Poland and Ukraine. Upper Miocene, Messinian assemblages from Spain, Algeria and Morocco are also similar to that from Malta.     

Limestone interbedded with submarine volcanics: the Early–Middle Miocene Conejo Volcanics, California

Carbonate sedimentation concurrent with submarine volcanism is very rare in the geologic record but is well displayed in the Early to Middle Miocene Conejo Volcanics of the central Santa Monica Mountains of southern California. Limestone occurs as lenticular deposits on the surface of composite flows units, as matrix within breccia of pebble- to cobble-size volcanic clasts, within primary voids extending down from flow surfaces, as lenses between flows within composite flow units, and as neptunian dikes. The common depositional sequence is of limestone lying on a flow and being overlain by hyaloclastic breccia. Limestone is not deposited on hyaloclastic breccia. Limestone deposition was controlled locally by relief on the sea floor that formed as the volcanic rocks accumulated. The limestone is predominantly skeletal packstone; volcanic clasts ranging in size from silt to boulders are locally common. Major constituent fossils are shallow-water bivalve mollusks, barnacles, serpulids, and regular echinoids; most are epifaunal and hard-substrate taxa in contrast to the soft-substrate and burrowing infaunal biota otherwise dominant in Cenozoic strata along the Pacific Coast of North America. The biota is diagnostic of a non-tropical, warm temperate environment. The limestone was deposited within a local basin that formed along the plate boundary at the western margin of the North American Plate. While volcanic rocks accumulated in the basin at bathyal depth, carbonate sediment accumulated on the outer-shelf margin of the basin and was transported intermittently into the basin by gravity flow. Neogene limestone occurs at only a few other sites in southern California. These have an origin that is similar to those in the Conejo Volcanics but differ in occurring with basin fill of diatomaceous sedimentary rocks rather than of submarine volcanics.     

Miocene invertebrate trace fossils from a braided river environment,western Nebraska,U.S.A

Lower Miocene cross-stratified sands of the Gering and Monroe Creek Formations exposed on Scotts Bluff National Monument in western Nebraska, U.S.A., were deposited by migrating sand bars in a braided river system similar to the modern Platte River in eastern Nebraska and, like the Platte, contain local lenses of parallel stratified sediment that accumulated in ponded areas of abandoned channels. During times of low discharge, broad areas of river bar sands and abandoned channel sediments were subaerially exposed on the Miocene river plain. These sediments, like those exposed in the Platte River today, were subjected to burrowing by insects and other animals.Trace fossils in Lower Miocene braided river deposits are: vertical shelter burrows, horizontal deposit-feeding burrows, bioturbated layers, and vertical passageways between bioturbated layers. The burrows are cylindrical to sub-cylindrical in cross-section, internally meniscate or massive, generally non-branching, and smooth walled. Shelter burrows are similar in shape and size to recent burrows dug by beetles in river sediment for protection from day-time temperatures, to pass the night, and to hibernate. The shelter burrows, deposit-feeding burrows, and vertical passageways in the Lower Miocene sediments occur in four distinct “populations” with modal diameters of 1–2, 3–4, 7–8, and 10–12 mm. The occurrence of both vertical and horizontal burrows in all four “populations” suggests that they could have been made by the same insect. “Populations” with modal diameters of 1–2, 3–4, and 7–8 mm also occur in modern Platte River sediment and are made by tiger-beetle larvae (3–4 mm) and heterocerid (1–2 mm) beetles. Miocene shelter burrows, deposit-feeding burrows, bioturbated layers, and vertical passageways, therefore, could have been formed by different types of beetles, and/or larval instars and adults of the same beetle species.     

Crinoids, hardgrounds, and community succession: The Silurian Laurel—Waldron contact in southern Indiana

Halleck, Margaret S.: Crinoids, hardgrounds, and community succession: The Silurian Laurel-Waldron contact in southern Indiana.
The uppermost surface of the Silurian Laurel Limestone at its contact with the Waldron Shale in southeastern Indiana was a hardground lithified prior to the deposition of the Waldron. Evidence for this conclusion is the presence of attached palmate crinoid roots, auloporid corals, and craniid brachiopods on the Laurel surface; the irregularity of the contact with the Waldron; and a pyritic veneer at this contact. The hardground apparently had a submarine origin. In addition to the attached epifauna mentioned above, algal-sediment 'clods' formed on this surface. Some of these accumulated around the crinoid stems, causing them to produce cirral extensions. The resulting community was a crinoid 'meadow' with algal growths forming sediment traps around and between the crinoids. Later stages of Waldron Shale deposition led to the development of a soft-bottom community.     

Evolution of pelagic swells from hardground analysis (Bathonian–Oxfordian, Eastern External Subbetic, southern Spain)

The Middle Bathonian to Middle Oxfordian interval in the Eastern External Subbetic (Betic Cordillera, SE Spain) is characterized by Ammonitico Rosso facies including various stratigraphic breaks. Five hardground-bounded units are recognized in relation to hiatuses in the ammonite record at the following stratigraphic boundaries: Hg1 (Lower–Middle Bathonian), Hg2 (Middle–Upper Bathonian), Hg3 (Lower–Middle Callovian), Hg4 (Middle–Upper Callovian), and Hg5 (Callovian–Oxfordian). Interesting features of these hardgrounds include their microfacies, ferruginous crusts and macro-oncoids, taphonomy of macroinvertebrates, trace fossils, neptunian dykes, and the hiatuses associated with each of them. The main hardgrounds (Hg1, Hg2, and Hg5) contain trace fossils of the Cruziana and Trypanites ichnofacies as well as abundant fossil macroinvertebrates with taphonomic features evidencing corrasion, early diagenesis, and reworking, indicating substrate evolution from softground to hardground. Neptunian dykes affected the trace fossils and ammonoid moulds, and their walls and the hardground surfaces were colonized by ferruginous microbial crusts. These features are characteristic of the External Subbetic pelagic swells, where the absence of sedimentation, sediment bypassing and erosion, and early diagenesis during relative sea-level falls produced hardgrounds. The neptunian dykes are indicative of tectonic activity in the areas of pelagic swells. Ferruginous crusts and macro-oncoids developed only on hardground surfaces and neptunian dykes walls prior to deposition of condensed bioclastic beds, which are interpreted as the first deposits after hardground development and are related to the onset of transgression. The varying ranges of the gaps as well as lateral facies changes are related to different local paleobathymetry controlled by the activity of listric faults.     

Die Fossilfcührung des erdfalls von nieheim (se-westfalen) und seine bedeutung für die paläogeographie imcampan und miozän das nordwestdeutsche tertiärbecken,nr. 27

A landfall in the east Westphalian-Lippean area contains a breccia of Keuper, Liassic and Miocene (marine Reinbekian) sediments. Within the Reinbekian sediments calcareous nannoplankton, diversified foraminiferal assemblages, ostracods, lamellibranchiates and gastropods, including a new subspecies ofAlvania (A.) curta, were found. Furthermore, foraminiferal and calcareous nannoplankton assemblages of Santonian to Campanian age are present. On the basis of these occurrences, the paleogeographic conception of the past coastline of the Westphalian Upper Cretaceous sea as well as of the southern extension of the boreal Middle Miocene sea can be revised. A gulf, stretching to the South, may have connected the North Sea basin with the basin of Mayence and the upper Rhine valley through the Hessian depression for certain periods during the Middle Miocene.     

The European Tertiary Neritiliidae (Mollusca, Gastropoda, Neritopsina): indicators of tropical submarine cave environments and freshwater faunas

The oldest freshwater neritiliid, Neritilia bisinuata , is described from the Middle Eocene of the Loire Basin. Another European species, N. neritinoides , ranging from the Lower Oligocene to Lower Miocene (Upper Burdigalian) is recognized; its habitat appears to have been freshwater, but very close to the sea. Two new marine neritiliid species from the Aquitaine Basin are described: Bourdieria favia sp. nov. from the Upper Oligocene and Pisulinella aucoini  sp. nov. from the Lower Miocene. A third undescribed species from the Lower Miocene is referred to the same family and related to Pisulinella . The Oligocene species has a strong spiral sculpture, a character completely absent in previously known neritiliid species. The genus Agapilia , founded on juvenile N. neritinoides and adult Vitta picta , appears to be a junior synonym of the genus Vitta. The associated occurrence of shells of the families Neritiliidae, Neritopsidae and Pickworthiidae (well-known inhabitants of Indo-West Pacific submarine caves) at Peyrère suggest the first occurrence of a characteristic assemblage of dark submarine caves during the Oligocene. Both factorial analysis and relative abundance show that at Peyrère these families are associated with other cryptic fossils (various gastropods, bivalves, Brachiopoda, corals, Annelida). However, there are indications of other submarine cave assemblages in various Cenozoic deposits from the Palaeocene to the middle Miocene.  © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 447–467.     

Diatom biostratigraphy of Late Miocene and Pliocene sediments of eastern Java (Indonesia)

A study of the marine diatoms of the Late Miocene to Pliocene Njepung section (Java) yield results that are in substantial agreement with Saint-Marc and Suminta (1979). The lower part of the Globigerina Marls belongs to the Late Miocene/Early Pliocene Thalassiosira convexa zone of Burckle (1972) while the middle of the formation belongs to the Middle Miocene Nitzschia jousea zone of Burckle (1972). An open ocean environment is indicated while the abundant presence of Thalassiosira nitzschioides suggests strong upwelling, at least in the lower part of the Globigerina Marls.     

Ecological controls on geometries of carbonate platforms: Miocene/Pliocene shallow-water microfaunas and carbonate biofacies from the Queensland Plateau (NE Australia)

Summary The Miocene and Pliocene of three ODP Leg 133 sites (812, 813, 814) record the biofacies evolution prior and during the partial drowning of the Queensland Plateau carbonate platform. Four major skeletal assemblages occur in the succession. The first, middle Miocene assemblage consists of a tropical chlorozoan association. The second assemblage, which records warm-temperate depositional conditions, lacks aragonitic skeletal elements. It is dominated by foraminifera and bryozoans. The third skeletal association (uppermost Lower Pliocene) contains green algae, foraminifera, and bryozoans. The last skeletal association is pelagic (ooze) and mainly consists of planktonic foraminifera and calcareous nannoplankton. The middle Miocene depositional geometry in the analysed transect of drill sites is that of a carbonate bank with a well-defined rim and a flank. During the late Miocene and early Pliocene carbonate ramps formed. Upper Miocene and lower Pliocene deposits in the drill holes are rich in large benthic foraminifera. Combination of micropaleontological with seismic data allows the reconstruction of a curve of relative sea level for the Tortonian and Messinian. The long term trend of relative sea level is characterised by a rise punctuated by four short term falls.Lepidocyclina (Nephrolepidina) rutteni is described from the Australian faunal province for the first time.     

Foraminiferal paleoecology of the Montpelier and lower coastal groups (eocene-miocene), Jamaica,West Indies

Two domains of carbonate deposition characterized mid-Tertiary Jamaica. After latest Cretaceous to Paleocene orogeny, submergence of insular paleo-Jamaica accompanied the strike-slip or extensional faulting associated with the formation of the Cayman Trench to the north. Differential subsidence along a series of peripheral subsea escarpments (Duanvale-Wagwater escarpment) produced relief in excess of 2000 m by the Late Eocene. Shoalwater limestones covered the slowly subsiding Cornwall-Middlesex platform, thus ending the supply of clastics to deep-sea bottoms north and east of the escarpment where contemporaneous planktonic-foraminiferal pelagites accumulated. Middle Eocene to Middle Miocene carbonate rocks deposited in the deep-sea represent a distinctive lithogenetic unit termed the Montpelier Group.A preponderance of globigerinacean and radiolarian tests characterizes lower Montpelier microfossil assemblages. Dominant benthonic forms include Melonis pompilioides, Fontbotia wuellerstorfi and species of Stilostomella and Pleurostomella. Available faunal criteria including the assemblage composition, depth preferences of extant species and recurrent morphologic-ecologic patterns suggest abyssal (2000 m) paleo-depths at the site of accumulation on a sediment apron near the base of the Duanvale-Wagwater escarpment. Computed from inferred paleodepth and estimated sedimentary thickness, Middle Eocene to Lower Miocene subsidence totals 2800 m. Biostratigraphic and paleoecologic data do not support the prevalent concept of a regional unconformity within the Montpelier.In the Middle Miocene, regional uplift led to the emergence of the Cornwall-Middlesex platform and to pronounced shoaling of marginal sea bottoms. Here, hemipelagic sedimentation resumed during the later Middle Miocene after the carbonate veneer on the adjacent platform was sufficiently eroded so as to expose noncarbonate rocks. See NAPS document No. 02395 for 67 pages of faunal reference lists, maps of sample locations and tables of foraminiferal occurrences. Order from ASIS/NAPS, c/o Microfiche Publications, 305 East 46th St., New York, N.Y., U.S.A. 10017. Remit with order $9.05 for photocopies or $5.55 for microfiche. Make checks payable to Microfiche Publications.     

Conceptual models for burrow-related, selective dolomitization with textural and isotopic evidence from the Tyndall Stone, Canada

The formation of dolomite is generally explained using models that reflect larger‐scale processes that describe the relationship between the supply and transport of Mg, and geochemical conditions that are amenable to the formation of dolomite. However, heterogeneities in the substrate, such as those made by bioturbating infauna, may play a more important role in dolomitization than has been previously considered. Burrow‐facilitated dolomitization is evident in the Ordovician Tyndall Stone (Red River Group, Selkirk Formation) of central Canada. The diagenetic fabrics present are attributed to dolomitizing fluids that both flowed through and evolved within burrow networks. Petrographic analysis suggests that two phases of dolomite formation took place. The first formed a fine‐grained, fabric‐destructive type that probably accompanied early burial; the second is a fine‐ to medium‐grained, locally sucrosic dolomite that is interpreted to have precipitated during later burial. Isotopic analysis supports the proposed paragenetic history: (1) an apparent linking of the stable isotopes ¹³C and ¹⁸O strongly suggests that the micrite matrix formed during very early diagenesis and was derived from seawater; (2) the initial phase of dolomitization is potentially microbially mediated, as evidenced by the enrichment of ¹³C; and (3) isotopic values for the second generation of dolomite reflect the mixing of ground water and resorbed early dolomite. This paper conceptualizes the physical and chemical conditions required for the formation of dolomite in association with burrow fabrics. The proposed model reveals a composite of biological and inorganic reactions that demonstrates the interdependence of sediment fabric, organic content and microbial interactions in the development of burrow‐mottled dolomitic limestone. It is suggested that where burrow‐associated dolomite occurs, it is most likely to develop in two stages: first, the byproducts of the degradation of organic material in burrows locally increase the permeability and porosity around burrow fabrics in shallow diagenetic depositional environments; and, second, the passing of burrowed media into deeper dysaerobic sediment is accompanied by the establishment of fermenting micro‐organisms whose byproducts mediate dolomitization.     

Upper Eocene to Middle Miocene ostracode faunas and paleo-oceanography of the North Coastal Belt,Jamaica, West Indies

The ostracode fauna of the Montpelier Group (Upper Eocene-Middle Miocene) exposed in the western part of the North Coastal Belt of Jamaica contains representatives of three paleo-environments. Allochthonous shelf and littoral species, characterized by abraded carapaces and eye tubercles, and a diverse group of archibenthal (slope) forms are present throughout. Species restricted to the World Ocean Psychrosphere (> 1000 m), notably Bradleya dictyon, Australoecia tipica, Agrenocythere hazelae and Macrocypris spp., first occur in sediments of earliest Miocene age (planktonic foraminiferal zone N4). Their presence establishes a minimum age for the entry into the Cayman Trench of frigid (<8–10°C) water masses drawn from the Atlantic thermohaline stratification.Upper Eocene and Oligocene assemblages are dominated by smooth, blind genera such as Krithe, Messinella and Bythocypris and lived in lower thermospheric conditions (10°C) at or near the base of the thermocline (700– 900 m). During the Early Miocene, downfaulting of the north island slope of Jamaica in response to southward tilting of the Nicaraguan Rise brought the Montpelier depositional site into contact with progressively deeper and colder water-masses. This subsidence culminated in the late Early Miocene; faunas of this age contain large numbers of Bradleya dictyon, Agrenocythere hazelae, Macrocypris sp. 1, Bairdia oarion and Bairdoppilata cassida. They suggest paleodepths of 1500–2000 m and the local presence of a 3–4° water-mass tentatively identified as the North Atlantic deep water. If this interpretation is correct, then the maximum sill-depth and water-mass configuration of the Miocene Cayman Trench have persisted to the present. Middle Miocene assemblages indicate a return to paleodepths of 1000–1500 m heralding the pronounced Upper Miocene to mid-Pleistocene tectonism which elevated Montpelier strata above sea level. An alternative view attributes the Miocene ostracode succession in the Montpelier to episodes in the development of the Atlantic circulation as recognized in the northeast Atlantic.Montpelier deposition took place either on a broad step intervening between the northern edge of the Clarendon Platform and the abyssal basins of the Cayman Trench or on a Tertiary analog of the existing north island slope. These results have emphasized the value of detailed taxonomic and morphologic studies of deep-sea ostracodes in geohistorical reconstruction.     

Trace fossils in middle to late triassic fluvial redbeds,pranhita‐godavari valley,south India

Several morphological varieties of trace fossils abound in Middle and Late Triassic fluvial redbeds in the Pranhita‐Godavari Valley, south India, including Skolithos, Palaeophycus, Taenidium, escape burrows, and a type of trace very similar to ‘small stuffed burrows’ from the Triassic of Greenland. Burrow morphology was influenced by local hydrodynamic conditions. The distribution of burrows was facies controlled; some forms are restricted to channel deposits whereas others occur only in floodplains. Vertical dwelling burrows (Skolithos) occur in both channel and floodplain deposits. Horizontal structures representing deposit feeding (Taenidium) are confined to nondepositional surfaces within parallel‐laminated sandstones having parting lineations that represent catastrophically emplaced sand‐sheets in channels and proximal floodplains. Vertical escape burrows are confined to what were slowly but continually accreting parallel‐laminated sands of channel bars. Horizontal dwelling burrows (Palaeophycus) and ‘small stuffed burrows’ are virtually restricted to the smaller sandsheets of floodplain drainage systems.

The burrow assemblages do not occur as recurrent associations throughout the redbed sequence, and variations in different stratigraphic levels seem to be controlled by minor differences within a broadly similar environment. The entire assemblage has components of both the Scoyenia and Rusophycus ichnocoenoses reported from East Greenland but may be considered as the Scoyenia ichnofacies characteristic of redbeds deposited in extensive floodplains dissected by small streams, even though no Scoyenia individuals are present.     

Plankton stratigraphy of the Early and Middle Miocene Kareem and Rudeis Formations in the central part of the Gulf of Suez,Egypt

The planktonic foraminifera and nannofossils of three wells in the Gulf of Suez penetrating the Early to Middle Miocene Upper Rudeis and Kareem Formations are attributed (from top to base) to the Middle Miocene Globorotalia peripheroronda Partial Range Zone (M6), the earliest Middle Miocene Praeorbulina sicana–Orbulina suturalis Interval Zone (M5), subdivided into the Praeorbulina glomerosa s. strict.–O. suturalis Interval Subzone (M5b) and the P. sicana–P. glomerosa s. str. Interval Subzone (M5a) and the Early Miocene Globigerinoides bisphericus Partial Range Subzone (M4b). The appearance of O. suturalis at the base of Subzone M5b represents the final stage of evolution of the Globigerinoides trilobus–Praeorbulina–Orbulina Lineage. In addition, the calcareous nannoplankton assemblages indicate the Sphenolithus heteromorphus Zone (NN5) and the Helicosphaera ampliaperta Zone (NN4). These biozones are well correlatable with those established by El-Heiny and Martini (1981, Geol Mediterr. Tome, VIII(2): 101–108) from the southwestern flank of the Gulf of Suez.     

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.     

Latest Guadalupian brachiopods from the Guadalupian/Lopingian boundary GSSP section at Penglaitan in Laibin, Guangxi, South China and implications for the timing of the pre-Lopingian crisis

A brachiopod fauna comprising nine species in eight genera from three closely spaced stratigraphic horizons of the same stratigraphic section is described for the first time from the Laibin Limestone in the uppermost part of the Maokou Formation in the Guadalupian/Lopingian (G/L) GSSP section at Penglaitan, Guangxi Autonomous Region, South China. The brachiopod assemblages are bracketed between two conodont zones: Jinogondolella xuanhanensis Zone below and Jinogondolella granti Zone above and, therefore, they can be safely assigned to the latest Capitanian in age. However, all but one of the nine brachiopod species from the Laibin Limestone carry strong early Lopingian (Wuchiapingian) aspect. Thus, the discovery of this brachiopod fauna not only suggests that some Lopingian brachiopod species had already appeared in the late Guadalupian (Capitanian); more importantly, it has also highlighted the fact that both the previously noted pre-Lopingian life crisis (or end-Guadalupian or Middle Permian mass extinction) and Lopingian recovery/radiation actually occurred in late Capitanian times, sometime before the G/L chronostratigraphic boundary. So far, the Penglaitan GSSP section provides the highest-resolution disappearance patterns of different fossil groups around the G/L boundary.