Biostratigraphic Information Research Articles

Polyphase halokinesis in the offshore Mississippi delta region, northern Gulf of Mexico

This paper reports results of a relatively small polyphase salt body about 65 km east of the mouth of the Mississippi River. The first phase of movement took place in the Early Cretaceous when salt of probable Louann (Middle Jurassic) age mobilized, moved upward, and formed a near-surface salt sheet overlying the Early Cretaceous sequence. The salt sheet became dormant during the period of sediment starvation in the Late Cretaceous through the early Miocene. Loading due to major influx of sediment began in the middle Miocene, remobilizing the salt which formed a secondary diapir that now penetrates almost to the seafloor. Seismic reflection data over the sheet and diapir together with biostratigraphic information from a nearby well provide evidence for the evolution of the salt body and the relationship of salt movement to sediment deposition.

Sequence Stratigraphy and Depositional Facies of Lower Ordovician Cyclic Carbonate Rocks, Southern Missouri, U.S.A.

ABSTRACT Lower Ordovician cyclic carbonate strata of southern Missouri were deposited in a warm, shallow, epeiric sea on a fully aggraded carbonate platform. Sedimentological characteristics distinguish the Jefferson City and Cotter dolomites from the underlying Gasconade and Roubidoux formations. Mixed carbonate-siliciclastic sedimentation characterizes the Roubidoux Formation, with sandstones accounting for up to 60% of sedimentation. The Gasconade, Jefferson City, and Cotter dolomites exhibit an increased occurrence of chalcedonic chert nodules in very similar shape and texture to the gypsum and anhydrite nodules common on modern sabkha supratidal flats. Casts of halite and ghosts of gypsum laths also exist in the Jefferson City and Cotter strata but are rarely found in the underlying units. Facies analysis from drill cores and outcrop sections provides the basis for identifying two major meter-scale cycle types. Type I cycles consist of algal stromatolites, tidal-flat laminites (mechanical and algal), ooid grainstones, wavy peloidal wackestones, and quartz sandstones interpreted as peritidal facies. They are the dominant components of the Roubidoux Formation, Jefferson City Dolomite, and Cotter Dolomite. Type II cycles consist mostly of subtidal facies such as strongly burrowed mudstone, thrombolite boundstone, and stromatolites. Type I cycles are thinner and represent highstand systems tracts, whereas the thicker type II cycles represent transgressive systems tracts and are dominant in the Gasconade Dolomite. The cycle stacking patterns, facies changes, and the intrabasinal correlatability of Fischer plots made from the widely spaced sections argue for a eustatic control on sea-level fluctuation on the platform. Interbasinal correlation with other North American basins is possible using biostratigraphic information and comparison of Fischer plots. Five Missouri sequences correlate with those described for other regions. The continent-wide uniformity in cycle stacking patterns indicates a primarily eustatic control on Lower Ordovician meter-scale cycle development. Regional tectonic and autocyclic controls probably account for general differences in sedimentation pattern among the correlated basins.

Stratigraphic framework for the Cambrian–Ordovician rift and passive margin successions from southern Quebec to western Newfoundland

The Taconian Humber Zone stretches from western Newfoundland to southern Quebec. The Early Cambrian slope succession in Newfoundland is found in the Curling Group, whereas in Quebec, various units were deposited during that first time slice. Biostratigraphic data allow correlation of the Curling Group with the Labrador Group in Newfoundland and with the newly time-constrained slope succession in Quebec. The end of the rift–drift transition is marked by a sea-level lowstand at the end of the Early Cambrian. The Middle Cambrian to latest Early Ordovician passive margin history recorded five cyclic sea-level fluctuations. Three of these cycles are recorded in the shallow-marine Middle to Late Cambrian platform (Port au Port Group) and slope sediments preserved in the Cow Head and Northern Head groups in Newfoundland. The biostratigraphic information assists correlation with Cambrian passive margin units in Quebec. Major sea-level lowstands are recognized along the continental margin in early–middle Late Cambrian (Steptoan) and in late Late Cambrian (Sunwaptan). Even if the Quebec succession can be tied with its Newfoundland correlative, some significant differences in the nature of Upper Cambrian slope conglomerates argue for a tectonic control on the depth of erosion of the Cambrian continental margin. The Lower Ordovician record of the passive margin consists of two depositional cycles (Tremadocian–Arenigian) separated by a sea-level lowstand. This last event is well expressed in platform succession and is also recognized in conglomerate units found in the slope succession.

The post-basaltic Palaeogene and Neogene sediments at Kap Dalton and Savoia Halvø, East Greenland

The Palaeogene flood basalts in East Greenland are part of the North Atlantic Igneous Province (NAIP) formed during continental rifting and opening of the northern North Atlantic (Saunders et al. 1997). Along the Blosseville Kyst in southern and central East Greenland the basalts are exposed onshore from Kangerlussuaq in the south to Scoresby Sund in the north (Larsen et al. 1989). The base of the volcanic succession is exposed at Kangerlussuaq and at Savoia Halvø whereas post-basaltic sediments are found at two isolated localities, Kap Dalton and Savoia Halvø (Fig. 2). These three outcrop areas are thus key sources for biostratigraphic data to constrain the onset and duration of the Palaeogene volcanism in East Greenland, and are widely used in reconstructions of the North Atlantic region during continental break-up (e.g. Clift et al. 1998; Dam et al. 1999). In August 2001 the Geological Survey of Denmark and Greenland (GEUS) carried out field work in the sedimentary successions at Kap Dalton and Savoia Halvø. This was the first visit by geologists to Kap Dalton since 1975, and it is expected that the new data will provide important new biostratigraphic information and help to refine models for the Palaeogene of the North Atlantic. This report, and the palynological study of the sediments immediately below the basalts at Savoia Halvø presented by Nøhr-Hansen & Piasecki (2002, this volume), present the preliminary results of the field work.

A multidisciplinary study of the Palaeogene succession offshore southern West Greenland

A project with the aim of amalgamating an interpretation of reflection seismic data from offshore southern West Greenland with a new interpretation of well data was finalised at the Geological Survey of Denmark and Greenland (GEUS) in 2001 (Chalmers et al. 2001b). As part of this study, seismic and depositional sequences between major regional unconformities of Danian and mid-Eocene age were delineated and dated.
 New palaeoenvironmental and sedimentological interpretations using dinoflagellate cyst, microfossil and nannoplankton stratigraphies and palaeoenvironmental interpretations from the five exploration wells drilled offshore West Greenland in the 1970s have been combined with a revised interpretation of lithology and correlated with the aid of seismic stratigraphy. The Qulleq-1 well drilled in 2000 was relinquished late in the project period (Christiansen et al. 2002, this volume), and it has therefore only been possible to incorporate biostratigraphic information from this well into the project.

Regressions and transgressions of the Baltic basin reflected by a new high‐resolution deglacial and postglacial lithostratigraphy for Arkona Basin sediments (western Baltic Sea)

Seismoacoustic profiles from the Arkona Basin show a late Pleistocene and Holocene succession of several distinct reflectors. The physical, sedimentological, mineralogical and geochemical properties of more than 30 sediment cores were analysed in order to assign these reflectors to specific sedimentary discontinuity layers. Additionally, AMS 14C data and biostratigraphic information were gathered. Based on this multi‐proxy approach, seven lithostratigraphic units (AI, AII, B to F) were distinguished. These consist of fine‐grained clay, silt and mud, and are separated from each other by thin basin‐wide traceable sandy layers (Sab‐Sef). The most sensitive parameter to mark the lithostratigraphic boundaries is the weight percentage of the grain‐size fraction >63μm. In addition, some of the quartz‐grain‐dominated sandy layers cause the strong reflection lines recorded in seismoacoustic profiles. The sandy layers are interpreted to reflect enhanced hydrodynamic energy induced by episodes of basin‐wide water‐level low‐stand conditions. These low stands resulted from water‐level drops that occurred frequently during the Baltic Sea's history and presumably affected the entire Baltic basin. The thick fine‐grained units AI, AII to F, in which coarser material is absent, represent water‐level high‐stands. We conclude that the units AI and AII are Baltic Ice Lake sediments deposited before and after the Billingen‐1 regression, respectively. We assign the most prominent sandy layer Sab to the final drainage of the Baltic Ice Lake (Billingen‐2), whereas the sandy layers between units B, C., D and E are related to the Yoldia Sea and Ancylus Lake regressions of the Baltic Sea's history. The uppermost fine‐grained unit F with its high organic carbon content contains marine sediments deposited after the Littorina Transgression. The macroscopically well‐visible sediment colour change from reddish/brown‐to‐grey, previously interpreted as a regional stratigraphic boundary, varies from core to core. It has been shown by our new data that this colour change has a diagenetic origin, and thus does not represent a stratigraphic boundary. Previous subdivisions therefore have to be revised.

Stratigraphy and sedimentology of the Permian of the Falkland Islands: lithostratigraphic and palaeoenvironmental links with South Africa

Comparison of the facies, ichnology and palaeocurrent patterns of the Permian of the Falkland Islands and the Dwyka, Ecca and Beaufort (part) groups in South Africa supports the hypothesis that the Falkland Islands lay east of South Africa in a rotated position prior to continental break-up. Key sections in the Falklands (NW Lafonia) and the Eastern Cape (Ecca Pass) would have lain about 200 km apart in Permian time. In the absence of accurate chonostratigraphic and biostratigraphic information from the Permian of the Falkland Islands, emphasis is placed on lithostratigraphic comparison. The Permian successions in both areas pass from diamictite through basin floor sediments, including organic-rich shale, rhythmites and turbidites. Mud-dominated delta front deposits culminating in channel deposits of a generally subaqueous delta top overlie the basin floor sediments. Points of close lithostratigraphic comparison are: (1) the diamictites have identical appearance, facies, and compatible palaeocurrents; (2) glacial sections are overlain by organic-rich black shales; (3) K-bentonites occur in basin-floor successions; (4) presence of basin-floor turbidite sandstone units with interbedded rhythmite units, and a distinctive Umfolozia/Undichna ichnofauna; (5) coarsening-up delta-front sequences are overlain by fining-up channel sandstone facies; (6) there is a close petrographic similarity indicating derivation of sandstones from a contemporaneous volcanic arc. The Permian successions of the two areas form parts of the fill of the eastern end of the main Karoo Basin, and were subject to the same influences of tectonic development, sediment derivation, eustatic variation and climatic change.

STRATIGRAPHY IN PHYLOGENY RECONSTRUCTION—RESPONSE

I too welcome this informed debate on the subject of the place of stratigraphy in phylogenetic reconstruction. Fisher et al. and Wagner have had the opportunity to clarify and expand on their respective approaches while Alroy chides me for not understanding the realities of correlation. The key areas of disagreement lie in how much reliance we think can be put on modeling evolution and to what extent we can prejudge the quality of the fossil record. Alroy emphasises that there is a practical limit on the resolution achievable from relative and absolute time scales. In the example he cites, a realistic lower bound is reached when time intervals are of about 0.7 Ma duration. In other situations different levels of resolution may be possible that are independent of taxonomic data. For example, our recent work (Gale et al., 2000) uses chalk-marl couplets that are thought to reflect Milankovitch cyclicity to define 20,000 yr time intervals. These units are correlatable over at least 100 km largely independent of biostratigraphic information. So limits on resolution imposed by technical difficulties of correlation are hardly objective, though they represent real thresholds/barriers. There is, however, an upper bound, reached when all occurrences are treated as falling within a single time interval, which is objective. Working at the upper bound corresponds to ignoring stratigraphic data in phylogeny reconstruction, while anything less than the upper bound uses stratigraphic information. What those wanting to use stratocladistics fail to clarify is why analyses should be carried out at, or close to, the finest scale of precision achievable. If the fossil record is both seriously incomplete and heterogeneous in terms of the environments that are preserved and rock outcrop area, as I (Smith, 2001) and others (e.g., Jackson and Johnson, 2001) think it is, then working with high precision could …

Differentiation of the British late Middle Pleistocene interglacials: the evidence from mammalian biostratigraphy

Acknowledgement of the climatic complexities of the marine oxygen isotope (δ 18O) record has inspired fresh investigations into methods of identifying and separating interglacial deposits on land. Biostratigraphical analysis of fossil mammalian assemblages, particularly those from long fluvial sequences, has proved to be a uniquely valuable technique in the differentiation of the various temperate episodes of the late Middle Pleistocene in Britain, thereby enabling a sequence of diagnostic mammalian assemblage-zones to be established. The scheme has provided an important means of correlation between geographically-distant localities and between different types of depositional environment. Using mammalian biostratigraphical information, this paper explores the evidence for three post-Anglian interglacials prior to the Last (Ipswichian) Interglacial, correlated with Stages 11, 9 and 7 of the oxygen isotope record, and presents the case for the recognition of much smaller-scale environmental and climatic oscillations within these interglacials, possibly corresponding to marine isotopic substages.

Upper Burgan Reservoir Description, Northern Kuwait: Impact on Reservoir Development

ABSTRACT The giant Albian upper Burgan reservoir in northern Kuwait is a major productive interval in both the Raudhatain and Sabiriyah fields. It is planned to increase production from the upper Burgan by over 300 percent through the application of field-wide waterflood. Phase 1 of seawater injection was started in 1999. A comprehensive geological study of the upper Burgan has included reviews of all core data, biostratigraphic information, and geochemical and petrographic analyses. The results indicate that the reservoir sandstones were laid down in a complex series of paralic environments ranging from shallow-marine to valley-fill channels. The resultant layering scheme was integrated with all available dynamic data to best define the reservoir architecture and flow units, and to construct a fine-grid 3-D geological model. The geological analysis has had a significant impact on reservoir development, influencing waterflood strategy, pattern orientation and expected performance. In the Raudhatain field, where reservoir connectivity is relatively high, a peripheral waterflood will be implemented (at least initially), whereas the complex structure and stratigraphy of the Sabiriyah field dictate a pattern flood.

New biostratigraphic information from the western part of the Hamburg klippe, Pennsylvania, and its significance for interpreting the depositional and tectonic history of the klippe

Biostratigraphic investigation of the graptolite and conodont faunas of the western part of the Hamburg klippe of eastern Pennsylvania permits a revised stratigraphic framework and new conclusions regarding its likely tectonic setting. Graptolite and conodont data reveal an almost complete Lower to lower Upper Ordovician zonal section. No Cambrian strata appear to be present, with the possible exception of the uppermost part. During Early to early Middle Ordovician time, medium- to fine-grained siliciclastics and minor carbonate sediments were deposited in a lower slope and rise setting. These sediments were consolidated and incorporated as olistoliths in an olistostrome, possibly as a trench-fill complex, during the Middle Ordovician (Darriwilian 3/4). This olistostrome, which contains large Lower and lower Middle Ordovician fragments within a matrix of shales, siltstones, and sandstones of Da 3/4 age, is herein named the Shellsville Member of the Dauphin Formation. Turbidites, here assigned to the Nyes Road Member of the Dauphin Formation, were also deposited during Da 3/4 time. These rocks interfinger with red beds of the here-named Manada Hill Member of the Dauphin Formation. The red shales, cherts, and associated rocks of the Manada Hill Member are pelagic deposits that range in age from at least early Arenig through middle Llanvirn time. These allochthonous rocks were emplaced as a gravity-generated klippe into the Martinsburg foreland basin during late Climacograptus bicornis or early Dicranograptus clingani time. These three members compose the Dauphin Formation (new) in the western part of the klippe area. Prior to emplacement of the allochthon, syntectonic flysch and scattered wildflysch of the Martinsburg Formation were deposited. Some graptolite faunas from the Martinsburg Formation, where contiguous with the klippe, may be slightly older than those known from areas farther from the klippe. This could indicate an earlier start of deposition in the Martinsburg foreland basin in advance of the allochthon. The klippe occupied a large space in the Martinsburg foreland basin and it diverted deposition in this area until it was finally covered by late Martinsburg age sediment. The Dauphin Formation is now structurally interleaved and folded with the Martinsburg Formation as a result of late Taconian and later Alleghenian tectonism.

Foramanifera and biostratigraphy of the Valdeteja Formation stratotype (Carboniferous, Cantabrian Zone, NW Spain)

The Valdeteja Formation is a lithostratigraphic unit of essentially Bashkirian age widely distributed through the Cantabrian Zone (Iberian Massif, NW Spain). It consists mainly of limestones with subordinate limestone breccias and some marly intercalations, deposited in shallow carbonate platforms and in the adjacent slope and basin settings (see Eichmuller, 1985). Its considerable thickness, rather continuous stratigraphic record and large lateral extent in the Cantabrian Zone have attracted the attention of geologists who have carried out a number of studies dealing with the palaeontological content, sedimentology, and palaeogeography of this formation. In spite of these diverse investigation, the precise age of the Valdeteja Formation, particularly the age of several fossiliferous beds defined at its stratotype, as well as the age of the top of the formation, remain obscure. This paper studies the foraminifera (mainly fusulinoideans) yielded by several beds throughout the type-section. The biostratigraphic information provided by these faunas allows us to establish the age of the mentioned beds in terms of the Russian stratigraphic scale. It confirms an early Moscovian age for the top of the type section, a matter of discussion for a very long time. Moreover, this research may have general interest in Carboniferous stratigraphy since it provides data on the fusulinoidean assemblages existing in western Europe during Bashkirian time, an interval containing a rather poor fossil record in this part of Eurasia.

Corrélations chimiostratigraphiques entre domaines marin et continental : application à une série du Miocène inférieur (Beynes-Châteauredon, Alpes-de-Haute-Provence, France)

Abstract The paucity of biostratigraphic information makes the stratigraphic attribution of continental series difficult to establish. To compensate for this lack of data we developed a chemostratigraphic analysis on Lower Miocene series (Alpes-de-Haute-Provence), based on the δ13C isotopic composition of the pedogenic carbonate glaebules preserved in the paleosols. The curve obtained proved to be an excellent tool: 1) at a regional scale, to correlate continental sections that show rapid lateral facies variations over a distance of nearly 10 km; 2) at a global scale, to correlate the fluctuations of the δ13C signal of the continental series with those of the marine realm, thus providing an excellent stratigraphic framework with a time resolution in the range of a hundred thousand years. The results obtained give an Aquitanian age to the first two thirds of the studied series and a Burdigalian age to the upper part. They also provide interesting results on the evolution of the vegetation in response to the Aquitanian marine transgression.

Sourcing mudsprings using integrated palaeontological analyses: an example from Wootton Bassett, Wiltshire, England

This paper presents comprehensive macro- and micropalaeontological analyses of taxa recovered from mud and stream lags disgorged from mudsprings at Wootton Bassett, Wiltshire, England. These mudsprings are unusual as they are found in a stable intraplate tectonic setting, but the techniques and provisos employed in this investigation can equally well be employed to source the material venting from other mudsprings, including those found in compressional tectonic settings. The Wootton Bassett mudsprings Site of Special Scientific Interest at Templars Firs (Wiltshire, England), has become renowned through considerable media coverage over the past few years, largely on account of the well preserved fossils exhumed in the outpourings of mud from a series of springs. However, it is emphasized that care must be exercised when undertaking sourcing investigations to ensure that the possibilities of contamination are minimized. Thus micropalaeontological analysis of freshly disgorged mud samples is shown to be a more accurate method of obtaining biostratigraphic information than the use of macrofossil material from stream lags. The erupted material contains biostratigraphically diagnosed microfossil species from several Later Jurassic ammonite zones, indicating sourcing from more than one subsurface stratigraphical horizon. Integrating this information with the local lithostratigraphy described herein, the source material for the mud can therefore be identified as the local Ampthill and Kimmeridge clays immediately underlying the site at a depth of around 10 m.

Late Tertiary tectonic subsidence on the northeast Australian passive margin: response to dynamic topography?

The carbonate platforms and adjacent troughs off northeast Australia record a phase of accelerated tectonic subsidence in the late Miocene/Pliocene. Previous attempts to analyse tectonic subsidence in this area were hampered by poor core recovery and dating uncertainties at some of the ODP (Ocean Drilling Program) Leg 133 sites on the Queensland Plateau, in particular at sites 812 and 814. In order to establish a general chronostratigraphy for these sites, we have integrated geophysical logs, biostratigraphic, lithologic, and seismic reflection data to identify and correlate Miocene hardgrounds on the Queensland Plateau to third-order eustatic sea-level lowstands on the Haq et al. [Haq, B.U., Hardenbol, J., Vail, P.R., 1987. Chronology of fluctuating sea levels since the Triassic. Science, Vol. 235, pp. 1156–1167] curve. This enables us to estimate ages where biostratigraphic information is poor. We have used sediment backstripping to compute tectonic subsidence histories for sites on the Queensland Plateau (811/825, 812, and 814), the Marion Plateau (815) and the Queensland Trough (823) in order to determine regional subsidence patterns. Results of these calculations show that, although the Leg 133 sites are located on a passive margin approximately 1000 km south of the Pacific–Australian plate boundary, they record a greater amount of subsidence than can be predicted from simple elastic models (post 9 Ma subsidence of 1300±200 m in the Queensland Trough, 650±200 m on the western margin of the Queensland Plateau, post 5 Ma subsidence of 500±30 m on its southern margin, and 660±50 m on the northern margin of the Marion Plateau). These models show that it is difficult to account for observed subsidence, either by means of thrust loading in Papua New Guinea, or by a combination of the latter and in-plane stresses originating from collision along the Australian–Pacific plate boundary. Alternatively, shear wave tomography [van der Hilst, R.D., Kennett, B.L.N., Shibutani, T., 1998. Upper mantle structure beneath Australia from portable array deployments. In: Brown, J., Dooley, J., Goleby, B., van der Hilst, R., Klootwijk, C. (Eds.), Structure and Evolution of the Australian Continent. Geodynamics Series 26, pp. 39–57.] displays a NNW–SSE trending band of anomalously high velocities in the upper mantle stretching from the Queensland Plateau to Indonesia. These anomalies likely reflect subducted slab material originating from late Eocene–late Oligocene subduction north of Papua New Guinea. Thus, we suggest that the observed post 9 Ma tectonic subsidence of the Queensland and Marion plateaus and Queensland Trough is largely caused by dynamic surface topography due to Australia's northeastern margin overriding a slab burial ground, modulated by flexural deformation resulting from collision tectonics north of Australia. The observed rates of tectonic subsidence are much slower than those of third-order sea-level changes, and can thus be differentiated from glacial-eustasy.

New Exploration Concepts for the Edwards and Sligo Margins, Cretaceous of Onshore Texas (E&P Notes)

We examined the potential in onshore Texas of the most prolific reservoirs found to date in the Gulf of Mexico basin, Cretaceous carbonates, and in particular the Edwards and Sligo formations. Two-dimensional (2-D) and three-dimensional (3-D) seismic data with lithologic and biostratigraphic information led to a detailed sequence stratigraphic framework. This framework resulted in a concentrated exploration effort in Lavaca County, a redefinition of the Edwards shelf margin, and confirmation of a major sequence boundary in the Sligo. The youngest Edwards margin appears to have stepped seaward a distance of more than 3 mi (4.8 km) from the position of the margin as indicated by the Word field. This seaward shift and repositioning of the margin is shown in 3-D seismic and well data. Recognized within the progradational package are distal slope wackestones, reef and bank complexes, and back-reef lagoonal deposits that are offset seaward across sequence boundaries. Reef and grainstone deposits are located far seaward of the commonly recognized margin and numerous exposure surfaces occur in the shelf deposits. Proximity to faulting after burial ensures the development of a plumbing system that enhances secondary porosity and provides a migration pathway for hydrocarbons. A Sligo debris play is based on a sequence boundary within the upper part of the Sligo in ferred from seismic geometry and surface exposures in Mexico. The seismic portrays a wedge geometry positioned downslope from the Sligo margin. Base-level change about the sequence boundary would have initiated coarse carbonate debris- and grain-flow deposition seaward of the Sligo shelf margin. Rapid deposition may have helped preserve porosity within the thick debris wedge. Data from reservoir analogs confirm that downslope carbonates can retain reservoir-quality porosity. Facies variation and slump faulting on the foreslope creates the potential for trapping, and juxtaposition to deep-water carbonates sets up the source and migration pathway. This undrilled wedge extends for hundreds of miles along the Sligo margin.

Distribution and biostratigraphy of latest Eocene to latest Oligocene Radiolaria from the Mahurangi Limestone, Northland, New Zealand

Radiolaria from the Mahurangi Limestone are generally common to abundant, well preserved, and the faunas reasonably diverse. However, all published information concerning these radiolarian faunas concentrates on the description of new species. This leaves useful data on location, density, abundance, preservation, biostratigraphy, and distribution unpublished. Data on 50 radiolarian‐bearing samples from 30 localities spanning the geographical range of the Mahurangi Limestone are presented. Forty‐three of these samples, from 25 localities, contain radiolarian age index taxa. More than 179 radiolarian taxa are identified, from over 89 genera, and diversity ranges up to 136 taxa per sample. Fifteen radiolarian index species can be identified within the Mahurangi Limestone, allowing many localities to be dated on radiolarian evidence alone. For age control, nannofossil age data from samples containing radiolarian age indicators are also presented. Radiolaria give an age range for the Mahurangi Limestone of latest Eocene to latest Oligocene. New or updated information includes a locality map, data on radiolarian densities, abundances and preservation for each sample, biostratigraphic information, a full list of radiolarian taxa identified from the Mahurangi Limestone, and tables of radiolarian distribution within the studied samples. A diagram correlating international and New Zealand stages with new information on South Pacific and tropical radiolarian zones for the latest Eocene to earliest Miocene is also provided, together with stratigraphic ranges for radiolarian index species used for dating the Mahurangi Limestone.

Middle Hettangian (Lower Jurassic) ammonites from Isle of Raasay, Inner Hebrides, and correlation of the Hettangian-lowermost Sinemurian Breakish Formation in the Skye area, NW Scotland

Synopsis Liasicus Zone (middle Hettangian) ammonites, allocated to a new species, Franziceras sorleyi, are described from Hallaig, Isle of Raasay and indicate that the Breakish Formation (formerly lower Broadford Beds) there is older than previously thought. The new finds have been integrated with the limited available biostratigraphic information from the rare record s of Hettangian and basal Sinemurian ammonites, and with local lithostratigraphy based on marker beds, to develop a new interpretation of correlations within the Skye–Raasay–Applecross area. This concludes that there was a diachronous early Jurassic transgression and facies change from the continental red beds of the Stornoway Formation into the marginal marine carbonate-dominated sediments of the Breakish Formation.

Palaeobiogeography of Tethyan ammonites during the Tithonian (latest Jurassic)

This study deals with the palaeobiogeographic distribution of Tethyan ammonites in the Tithonian. In particular, the relationships between ammonites of the Mediterranean Tethys, East Africa, Caribbean and Southeast Pacific areas are discussed. The study of palaeobiogeographical raw data allows one to recognize palaeobiogeographic patterns and delimit provinces and to infer palaeobiogeographical processes and, in some cases, palaeogeographical (geological) processes. Biological and physical factors affecting the palaeobiogeographic distribution of the ammonites are reviewed prior to a discussion of the distributional patterns. The analysis is constrained by different factors such as taxonomy, sample size, accuracy of the biostratigraphic information, etc. The highly problematic taxonomy of the family Ataxioceratidae hampers the use of quantitative analyses, only allowing `phenetic' definitions of provinces. Some of the Tethyan palaeobiogeographic provinces already known in the literature are dealt with further. In particular the subdivision into Mediterranean and Sub-Mediterranean provinces (or sub-provinces), that is quite clear at the scale of the entire Jurassic period, is rejected in the Tithonian though a phase of faunal separation is recorded during the transition between the early and late Tithonian. The ammonite assemblages in the shelves were less diverse and different from those of the distal, pelagic areas. Dispersal is recognized as an important process in ammonite palaeobiogeography although objective location of centres of origin is impossible. Vicariant phenomena certainly occurred but in marine environments barriers that separate areas of distribution instead of portions of space cannot be delimited objectively. The `barrier' is certainly represented by the different palaeoenvironmental contexts (shelf or pelagic habitats). The palaeobiogeographic distributions observed were produced by a complex of concurrent biogeographic processes.

Magnetostratigraphic correlation of Paleogene sequences from northwest Europe and North America

Research Article| May 01, 1999 Magnetostratigraphic correlation of Paleogene sequences from northwest Europe and North America Guy M. Rhodes; Guy M. Rhodes 1Department of Oceanography, University of Southampton, Southampton SO14 3ZH, UK Search for other works by this author on: GSW Google Scholar Jason R. Ali; Jason R. Ali 2Department of Earth Sciences, University of Hong Kong, Hong Kong, People's Republic of China Search for other works by this author on: GSW Google Scholar Ernie A. Hailwood; Ernie A. Hailwood 3Core Magnetics, Sedbergh, Cumbria LA10 5JS, UK Search for other works by this author on: GSW Google Scholar Chris King; Chris King 4School of Earth and Environmental Sciences, University of Greenwich, Medway Campus, Chatham Maritime, Kent ME4 4TB, UK Search for other works by this author on: GSW Google Scholar Tom G. Gibson Tom G. Gibson 5Department of Paleobiology, Smithsonian Institution, Washington, D.C. 20540, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Guy M. Rhodes 1Department of Oceanography, University of Southampton, Southampton SO14 3ZH, UK Jason R. Ali 2Department of Earth Sciences, University of Hong Kong, Hong Kong, People's Republic of China Ernie A. Hailwood 3Core Magnetics, Sedbergh, Cumbria LA10 5JS, UK Chris King 4School of Earth and Environmental Sciences, University of Greenwich, Medway Campus, Chatham Maritime, Kent ME4 4TB, UK Tom G. Gibson 5Department of Paleobiology, Smithsonian Institution, Washington, D.C. 20540, USA Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1999) 27 (5): 451–454. https://doi.org/10.1130/0091-7613(1999)027<0451:MCOPSF>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Guy M. Rhodes, Jason R. Ali, Ernie A. Hailwood, Chris King, Tom G. Gibson; Magnetostratigraphic correlation of Paleogene sequences from northwest Europe and North America. Geology 1999;; 27 (5): 451–454. doi: https://doi.org/10.1130/0091-7613(1999)027<0451:MCOPSF>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Using all available biostratigraphic information and our own extensive magnetostratigraphic database, we have attempted to assess the synchronicity of depositional cycles recorded in the Paleogene epicontinental deposits on both sides of the North Atlantic as stage two of a four-stage global assessment of the eustatic sea-level model. Our conclusion is that the depositional histories of the U.S. Gulf of Mexico–Atlantic coastal plain and the North Sea basin show many similarities, on a variety of time scales, over the interval 60–46 Ma. Considering the tectonic imprint of the northeast Atlantic opening on the North Sea basin sea-level record for part of this time, it must give some weight to the claim that eustasy is the dominant mechanism controlling deposition on passive continental margins. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.