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The paraphyletic group Grylloblattida, formerly included in the Protorthoptera sensu lato, is of great importance for the phylogeny of some 'polyneopterous' orders, because it is currently assumed to contain the sister groups of modern Plecoptera (stoneflies) and Grylloblattodea. We present new discoveries and new observations and interpretations concerning this crucial assemblage. Lodevopterum angustus new genus and species and Depressopterum minutus new species are described from the Upper Permian of the Lodeve Basin (Herault, France). The 'Grylloblattida' from Commentry (Allier, France; Upper Carboniferous) are revised: the family Protoblattinidae Meunier, 1909a is restored after the redescription of the type species Protoblattina bouvieri Meunier, 190%; the family Stenoneuritidae Lameere, 1917 is revised; Palaeocixius fayoli Handlirsch, 1906b and Protoblattina giardi Meunier, 1921 are synonymized with Palaeocixius antiquus Brongniart, 1893, followed by a discussion on the possible familial attributions of this genus. The affinities of the poorly known family Protoperlidae Brongniart, 1885a are discussed after a critical compilation of the available data, i.e., Protoperla boltoni Lameere, 1917 is considered as Grylloblattida incertae sedis and Polyetes elegantissima Meunier, 1921 is transferred into Laurentiaupterum new genus and assigned to Paraphenopteridae new family. Close phylogenetic relationship of Atactophlebia termitoides Martynov, 1928 (Tikhiye Gory, Tatarian Republic, Russia; Upper Permian) and Pinidelia sukatshevae Storozhenko, 1994 (Tyulkino, Perm region, Russia; Upper Permian) is based on a new interpretation of their forewing venation. The recent taxonomy and phylogeny of the Grylloblattida proposed by Storozhenko (1998, 2002) are refuted. The current concepts of Protorthoptera, Plecopteroid Assemblage, and Grylloblattida are compared.

This study visualizes, quantifies, and evaluates relationships between bedrock geology and topography through the use of GIS. The study area contains weakly consolidated Permian-aged sandstone and shale of slightly differing ages that have been dissected by the regional drainage. The erosion of these rocks has produced a subtle but well-defined topography. Data for this work were obtained from a 30 m resolution digital elevation model (DEM) and the bedrock geology map of Oklahoma. Numeric values of local slope angle and relief were extracted from the DEM and associations with geologic formations were summarized and compared. The maps reveal that local topographic variations are dependent on the relative abundance of sand to shale in the underlying bedrock. This finding is significant because the topographic expression is so subtle that associations between topography and bedrock geology would not be easily recognized or quantified with conventional field techniques. To identify controls on topography, sandstone thicknesses were measured in outcrop and the bulk density of field samples was measured in the laboratory. We find that sandstone thickness is greater in areas of higher local relief and thinner in areas of lower relief. |n contrast, bulk density, used as a proxy for susceptibility to erosion, is not significantly different between areas. These findings suggest that presence and thickness of sandstone, even if weakly consolidated, plays a role in determining topographic expression of bedrock. This GIS-based technique, when constrained by geology, can enhance the quality of multiuse mapping programs in the geosciences, agriculture, and civil engineering. Keywords: GIS, topography, sedimentology, stratigraphy, Oklahoma, Permian.

Biostratigraphical study of the early to mid-Ordovician conodont fauna from ribbon-banded radiolarian cherts of the middle Burubaital Formation in Central Kazakhstan reveals an almost complete succession of conodont biozones from the late Tremadocian to the early Darriwilian. During this interval, biosiliceous sediments were deposited in basinal environments, inhabited by lingulate brachiopods, sponges, pterobranchs and caryocaridids in conditions of high fertility and primary productivity of surface water. The community structure of taxonomically diverse conodont assemblages typifying open oceanic environments is not significantly different from that of epicratonic basins of the North Atlantic conodont province. The regional increase of oxygenated bottom waters at the base of the Oepikodus evae Biozone is possibly related to considerable changes in palaeo-oceanographical circulation patterns. The finds of three natural clusters of Prioniodus oepiki (McTavish) enable us to propose an emended diagnosis of this species. Keywords: radiolarites, Conodonta, Kazakhstan, Ordovician.

Because many survivors of mass extinctions do not participate in postrecovery diversifications, and therefore fall into a pattern that can be termed 'Dead Clade Walking' (DCW), the effects of mass extinctions extend beyond the losses observed during the event itself. Analyses at two taxonomic levels provide a first-order test of the prevalence of DCWs by using simple and very conservative operational criteria. For four of the Big Five mass extinctions of the Phanerozoic, the marine genera that survived the extinction suffered [approximately equal to] 10-20% attrition in the immediately following geologic stage that was significantly greater than the losses sustained in preextinction stages. The stages immediately following the three Paleozoic mass extinctions also account for 17% of all order-level losses in marine invertebrates over that interval, which is, again, significantly greater than that seen for the other stratigraphic stages (no orders are lost immediately after the end-Triassic or end-Cretaceous mass extinctions). DCWs are not evenly distributed among four regional molluscan time-series following the end-Cretaceous extinction, demonstrating the importance of spatial patterns in recovery dynamics. Although biotic interactions have been invoked to explain the differential postextinction success of clades, such hypotheses must be tested against alternatives that include stochastic processes in low-diversity lineages--which is evidently not a general explanation for the ordinal DCW patterns, because postextinction fates are not related to the size of extinction bottlenecks in Paleozoic orders--and ongoing physical environmental changes.

We grouped the fossil records of marine animal genera into suites defined by function and physiology. The stratigraphic coherence of the resulting diversity history indicates the importance of ecological structure in constraining taxonomic richness through time. The proportional representation of major functional groups was stably maintained for intervals as long as 200 million years, despite evolutionary turnover and changes in total diversity. Early Paleozoic radiations established stable ecosystem relationships, and thereafter only the great era-bounding mass extinctions were able to break patterns of incumbency, permitting the emergence of new community structures with distinct proportional diversity relationships.

The Carolina Zone is an amalgamation of mainly Neoproterozoic--Early Paleozoic metaigneous-dominated terranes that are clustered along the eastern flank of the southern Appalachians. These terranes are distinguished from other divisions of the orogen by a commonality in gross geologic content and by their close spatial association. They are considered exotic relative to Laurentia on the basis of stratigraphic and tectonic evolution, paleontology, and position in the orogen analogous to that of exotic terranes in the northern Appalachians. They are probably peri-Gondwanan in origin. Within this first-order identity, the terranes exhibit remarkable heterogeneity, with respect to deposition, magmatism, and tectonothermal overprint. The depositional--magmatic history of the zone is viewed in three broad stages, including: (I) pre-600 Ma, (II) ca. 590-560 Ma, and (III) younger than ca. 550 Ma. Although each stage records significant felsic volcanism, there are few compelling stratigraphic linkages between terranes. Stage III plutonism may form a link between the two largest terranes in the zone. The isotopic evolution of the zone reflects the stratigraphic heterogeneity; isotopically juvenile magmatism in some terranes is coeval with more crustally evolved magmatism in others. The tectonothermal history of the zone is heterogeneous, producing a patchwork of suprastructural and infrastructural elements of different ages. Major tectonothermal events responsible for this pattern span the Neoproterozoic--earliest Cambrian, the Late Ordovician--Silurian, and the late Paleozoic. Evidence for regionally extensive events in the zone is sparse and such a fundamental concept as its time of accretion to Laurentia is speculative. The central Piedmont shear zone, a late Paleozoic ductile thrust that defines the western limit of the Carolina Zone, marks the final emplacement of the zone against Laurentian elements. Keywords: Carolina zone; Carolina terrane; Southern Appalachians; Neoproterozoic arcs; peri-Gondwanan terranes

A new compilation of deep seismic reflection data, in combination with the results of recent geological and isotopic investigations, provides the basis for significantly refined structural and evolutionary models of the Middle Urals. Many of the major structural boundaries observed at the surface (e.g. Main Uralian Thrust, Main Uralian Normal Fault, Serov-Mauk Fault, Prianitchnikova Shear Zone) can be followed on the seismic reflection data to depths of 8-15 km. Only a few features can be traced through the horizontal to shallow dipping zones of middle-crustal reflectivity that extend beneath much of the Middle Urals. Exceptions might be the Deevo Thrust and a newly discovered deep band of moderately dipping reflections beneath the West Siberian Basin that may represent the remnants of an ancient subduction zone. The reflectivity of the lower crust and Moho are similar beneath the hinterland of the Urals and below the western part of the West Siberian Basin, suggesting that in both places they have the same extensional origin. Accretion of various exotic terranes to the eastern margin of Baltica during Late Palaeozoic time involved considerable shortening of the continental margin. The accreted terranes (e.g. Tagil, Petrokamensk and Alapaevsk Arc Complexes) consist mostly of island-arc material formed during Mid- and Late Palaeozoic time. Closely associated with the island arcs are several high-grade metamorphic complexes (e.g. Salda and Murzinka--Adui Complexes) that were exhumed during and after Late Palaeozoic convergence. Towards the end of the orogeny, several north-south-trending strike-slip faults (e.g. Sisert Fault) were active. After the orogeny, major periods of tectonism and magmatism in the Middle Urals resulted in the extrusion of the Siberian trap basalts, crustal stretching and/or underplating, and the formation of the West Siberian Basin, the planet's largest intracontinental sedimentary basin. Finally, a period of renewed thrust faulting, often reactivating older faults, led to the inversion of the Mesozoic basins. Keywords: Uralide Orogen, West Siberian Basin, Palaeozoic, Mesozoic, seismic profiling.

Three important collections of European Devonian and Lower Carboniferous polyplacophorans have been located in United States institutions. The specimens provided a basis for better description of important characters and clarified some taxonomic assignments. Two new polyplacophoran species are in the collections, Helminthochiton carpenteri from the Devonian of Germany and Pterochiton absidatus from the Lower Carboniferous of Belgium. Beloplaxus sagittalis (Sandberger and Sandberger, 1853-1855) is recognized as a multiplacophoran and a new genus and species of turrilepadid, Bouturrilipas scutatus, is proposed.

Lake deposits of the Pagoda Formation (Upper Carboniferous?--Lower-Permian) at Mt. Butters, Shackleton Glacier area, central Transantarctic Mountains, Antarctica, yield a low diversity biota including a new species of conchostracan, Cyzicus (Lioestheria) shackletonensis. Locally, conchostracans occur in large numbers near the tops of thin coarsening-upward cycles in siliciclastic sediments. Regionally, the Pagoda Formation consists of glacigenic deposits of the Gondwanide ice sheet that covered much of the land in southern high latitudes. At Mt. Butters, the lake deposits document the presence of an ice-margin lake in front of the advancing ice sheet. Deposition from suspension within the lake was interrupted by introduction of sand and silt deposited in the conchostracan-bearing, upward-coarsening sequences. Conchostracans of the Pagoda Formation are associated with other arthropods (euthycarcinoids and ostracodes), and wood fragments; burrows produced by small animals moving just beneath the sediment surface are abundant in some horizons. Few conchostracan occurrences are known from the Carboniferous-Permian of Antarctica; this is the second recorded occurrence, and it increases the number of described species to three.

Conodonts were mostly small, elongate, eel-shaped marine animals that inhabited a variety of environments in Paleozoic and Triassic seas. Although long enigmatic, conodonts are now regarded as vertebrates and their closely controlled fossil record is not only the most extensive of all vertebrates, but it also makes conodonts the fossils of choice in upper Cambrian through Triassic biostratigraphy. Conodonts were soft-bodied except for a variety of phosphatic elements that. formed a distinctive feeding apparatus. Post-mortal dissociation of the apparatus and subsequent jumbling of its elements on the sea floor led, from 1856 to about 1966, to development of an artificial, form-based taxonomy that was utilitarian, but clearly unsatisfactory as a vehicle for understanding the group in biologic terms. Natural assemblages of elements, discovered between 1879 and 1952, have been interpreted as undisturbed skeletal apparatuses, and in the mid-1960s it was determined that original composition of the apparatuses of many species could be reconstructed and statistically evaluated from collections of disjunct elements by various grouping procedures. These determinations led to an emphasis on multielement taxonomy by most (but not all) students of conodonts. Even so, only about a third of the approximately 550 valid conodont genera, have been established (or re-interpreted) in multielement terms and this makes any of the several extant schemes of suprageneric classification phylogenetically suspect. We comment on a recent scheme that recognizes 41 families assigned to some 7 orders, and suggest how it might be modified so as to square with principles of phylogenetic systematics.

Twentieth century fossil gastropod systematics relied extensively on neontological paradigms. However, recent appreciation of the extant gastropod diversity suggests that those early paradigms provided very unsound models. This likely is a greater problem for Paleozoic taxa than for Meso-Cenozoic gastropods because Meso-Cenozoic taxa frequently have easily recognized extant relatives whereas Paleozoic taxa frequently do not. Also, many of the taxa that apparently diverged in the Paleozoic now are limpets and retain little information about the morphologies of their coiled ancestors. Snails could be a model taxon for investigating macroevolutionary patterns because of the clade's dense fossil record. However, paleontologists usually study only adult shells (teleoconchs), and many malacologists maintain that teleoconch characters reflect phylogeny poorly if at all. This is important because many macroevolutionary hypotheses make their most specific predictions given phylogeny. Studies evaluating species- or genus-level relationships typically use more shell characters and states than do studies evaluating suprageneric relationships, as expected if shells evolve rapidly. Monte Carlo tests reject a null hypothesis that rates of homoplasy are equal among shell and soft-anatomy characters for two neogastropod clades, but suggest that these rates differ by less than an order of magnitude. Finally, teleoconch characters fail to unite bellerophontiform species with gastropod muscle scars but successfully unites clusters bellerophontiform species with tergomyan muscle scars. These results corroborate the conventional wisdom that teleoconch character distributions reflect abundant homoplasy, but the results also suggest that these distributions reflect phylogeny, too. If we can control the effects of homoplasy, then gastropods are an excellent 'model' group for testing macroevolutionary hypotheses such as changing rates of evolution. Two obvious candidates are rates of morphologic evolution among basal neogastropods, and rates of molecular evolution within clades radiating after the K/T mass extinction.

The provenance of turbidites from the predominantly Arenig-aged Manx Group has been constrained using petrographical and geochemical techniques. Petrographical analysis of sandstones reveals that mono- and poly-crystalline quartz grains of cratonic origin are dominant. Major, trace and rare earth element concentrations in both sandstones and mudstones complement the petrographical data indicating that the source of the sediments consisted of quartzose basement and mature sedimentary rocks. There is little evidence of a juvenile volcanic input but a minor palaeovolcanic component of active continental margin affinity is present. There are indications of a more immature character in the oldest units but, on the whole, geochemical data from the Manx Group suggest an overall passive margin setting. These results suggest that Eastern Avalonia was attached to Gondwana during deposition of the Manx Group and that Iapetus oceanic crust did not subduct beneath the region before the end of the Arenig. Keywords: Manx Group, Avalonia, Iapetus, provenance, geochemistry.

Paleoproterozoic (1770-1735 Ma) bimodal volcanic rocks in central Colorado have been considered to represent southward growth of Laurentia by arc accretion. Although the bimodality of these rocks suggests an extensional continental setting rather than continental or oceanic arcs, there has been little evidence for pre-1800 Ma crust south of the Wyoming craton other than the 1840 [+ or -] 1 Ma Elves Chasm pluton in the Upper Granite Gorge of the Grand Canyon, Arizona. We report SHRIMP U-Pb ages of inherited zircons from metarhyolites and plutons in central Colorado that are latest Archean-earliest Proterozoic (2520-2000 Ma) and Trans-Hudson-Penokean (1878-1814 Ma). Associated quartzites contain detrital zircons with mean ages of 1735 Ma, indicating only local derivation. A meta-arkose, however, contains detrital zircons of Trans-Hudson-Penokean and Archean ages. We believe it likely that the 1900-1800 Ma Trans-Hudson-Penokean orogens, including Archean enclaves, extended farther south and west than is currently thought, and were the source of the bimodal volcanic rocks and associated plutons during the period 1770-1700 Ma. Keywords: Colorado, crustal growth, geochronology.

A description of the fossil arthropod Eurypterids is presented, which ranged from the Lower Ordovician to the Permian era. Topics include anatomy, respiration, locomotion, and habitat.

The Synapsida are a carnivorous vertebrate group that are colloquially referred to as mammal-like reptiles. Synapsids typically had long snouts with small but numerous teeth, and was able to bring down, kill and eat prey nearly as large as itself.

Whole-rock Chemical composition and [sup.11]B/[sup.10]B isotope ratios in tourmaline was investigated to study the geochemical recycling of boron during the evolution of the Andean basement from the Palaeozoic to Mesozoic. In the basement (Cambrian to Ordovician high-grade paragneisses, migmatites and orthogneisses, the Eocambrian Puncoviscana Formation, and Paleozoic-Mesozoic granitoid igneous rocks) whole-rock B contents are generally below 100 ppm, but B contents of ~1 wt% are found in cogenetic aplite and pegmatite dikes and in tourmaline-quartz rocks. In the metasedimentary rocks, no systematic variation in B content because of metamorphic grade and no correlation of B with other incompatible elements are apparent. Tourmalines from the high-grade metamorphic basement yield [delta.sup.11]B values ranging from -11.2 to -6.8 [per thousand] and isotope fractionation during migmatisation was small. Metamorphic tourmalines from the Puncoviscana Formation have [delta.sup.11]B values between -6.3 and -5.8 [per thousand]. The calculated (corrected for fractionation) [delta.sup.11]B values of -6 to -2 [per thousand] for the sedimentary protolith of the metamorphic basement indicate a continental B source with subordinate marine input. Tourmalines from Palaeozoic and Mesozoic granitoids display an identical range of [delta.sup.11]B values from -12 to -5.3 [per thousand] and indicate a similarly homogeneous B source throughout time. Tourmalines from pegmatites and tourmaline-quartz rocks record the average [delta.sup.11]B values of the parental granitic magma. We assume that B in the Palaeozoic and Mesozoic granitoids is derived from the local metamorphic basement supporting the hypothesis that recycling of the lower Palaeozoic crust is the dominant process in granitic magma formation from Palaeozoic to Mesozoic.

Magnetic susceptibility data from marine rocks can be used for global correlation due to synchronous variations in global erosion. We show here that the magnetic susceptibility signature, found in two forms, resides mainly in paramagnetic and other detrital constituents in most marine rocks. The first form is a short-term, low-magnitude, high-frequency cyclic climate signature that is often useful for regional correlation. The second form is a longer term, higher magnitude, low-frequency signature resulting from transgressive and regressive events that can be used for global correlation. Fluctuations in detrital input, due to eustatic-based erosion, are the primary cause of events. These fluctuations are driven by large-scale processes such as global orogenic cycles. However, variations in carbonate productivity cannot be ruled out when explaining the low-magnitude climate-driven cyclicity also observed in magnetic susceptibility data sets. Keywords: global correlation, climate cycles, magnetic susceptibility, Paleozoic, Devonian, Morocco.

Lower Palaeozoic rocks in the Karadere-Zirze area, east of Safranbolu (Pontides, northern Turkey), range from Early Ordovician to Silurian. Overlying the probably Tremadoc Bakacak Formation are Aydos Formation quartzites, followed conformably by the Karadere Formation, dated as Early Arenig to Early Llanvirn by means of graptolites which are assigned to seventeen genera and include three new forms: Eoglyptograptus bouceki, Prolasiograptus haplus praecursor and Undulograptus? mui. Late Arenig trilobites from the Karadere Formation include Bergamia, Cyclopyge, Dionidella?, Leioshumardia and Seleneceme. In the Limestone Member of the overlying Ketencikdere Formation, uncommon trilobites suggest only a mid- to late Ordovician age, but conodonts with Colour Alteration Index 5-6 indicate the Amorphognathus tvaerensis Biozone (early Caradoc). Macrofossils are rare in the Siltstone Member, but conodonts from the middle of the unit suggest the highest subzone of the A. tvaerensis Biozone; the youngest visible strata are, on acritarch evidence, at least as high as Caradoc, but the Ashgill is not confirmed and the contact with overlying Silurian rocks is unexposed. The Findikli Formation comprises: a Lower Member, black argillites with Llandovery graptolites and acritarchs; and an Upper Member, grey shales with late Wenlock graptolites, overlain unconformably by Devonian rocks. The succession differs significantly from contemporaneous deposits in southern Turkey and its affinities lie with western Europe, including the Welsh Basin.

In the foothills of the Great Smoky Mountains in Tennessee, low-grade metamorphic rocks of the Walden Creek Group, Ocoee Supergroup, contain a fossil assemblage composed of trilobites, bryozoans, ostracodes, pelmatozoans, algae, and agglutinated foraminifers, indicating a Silurian or younger age. The new paleontological data contradict older ideas on the Neoproterozoic age of the Walden Creek Group. The Walden Creek Group was not deposited in a continental rift basin preceding the opening of the Iapetus ocean but, possibly, in a pull-apart basin formed in a transtensional event during the Acadian orogeny. There is no field evidence indicating that the Walden Creek Group is separated from the lower units of the Ocoee Supergroup by a basin-wide unconformity and hiatus. A tentative geodynamic model is presented for the Ocoee Supergroup basin; the model is dependent on paleontological data indicating a Paleozoic age for the Walden Creek Group and concentrates on lithologic, petrographic, and basin characteristics. The model allows for the possibility that the entire Ocoee Supergroup was deposited in a Paleozoic transtensional basin. Keywords: Great Smoky Mountains, microfossils, Ocoee Supergroup, southern Appalachians, stratigraphy, tectonic model.

Across the Appalachian orogen of New England, the splitting of core-refracted shear waves from a wide range of arrival directions indicates the presence of two nearly uniform horizontal layers of anisotropic upper mantle. The anisotropy in the lower layer has a fast axis nearly parallel to the absolute motion of the North American plate and thus is attributed to basal shear as the plate plows through asthenospheric mantle. The anisotropy of the upper layer is inferred to be a fossil fabric, residing in lithospheric mantle. The finite extension direction of the upper fabric is subhorizontal and oriented normal to the local trend of the Appalachian orogen. The upper fabric is consistent over a broad region beneath and west of the New England Appalachians, which indicates that it formed after Devonian closure of the lapetus ocean, probably during or after the Paleozoic Acadian and Alleghany orogenies. Tectonic scenarios for synconvergent or postconvergent extension, developed for Tibet, predict rapid surface uplift and increased heat flow due to lithospheric thinning, consistent with coeval late orogenic mantlederived magmatism in both the northern Appalachians and Morocco.

When the highlands of Arabia were still covered with an ice shield in the latest Carboniferous/Early Permian period, separation of Gondwana started. This led to the creation of the Batain basin (part of the early Indian Ocean), off the northeastern margin of Oman. The rifting reactivated an Infra-Cambrian rift shoulder along the northeastern Oman margin and detritus from this high was shed into the interior Oman basin. Whereas carbonate platform deposits became widespread along the margin of the Neo-Tethys (northern rim of Oman), drifting and oceanization of the Batain basin started only in Late Jurassic/Early Cretaceous time. Extensional tectonics was followed in the Late Cretaceous by contraction caused by the northward drift of Greater India and Afro-Arabia. This resulted in the collision of Afro-Arabia with an intra-oceanic trench and obduction of the Semail ophiolite and the Hawasina nappes south to southwestward onto the northern Oman margin approximately 80 m.y. ago. During the middle Cretaceous, the oceanic lithosphere (including the future eastern ophiolites of Oman) drifted northwards as part of the Indian plate. At the Cretaceous-Palaeogene transition (approximately 65 Ma), oblique convergence between Greater India and Afro-Arabia caused fragments of the early Indian Ocean to be thrust onto the Batain basin. Subsequently, the Lower Permian to uppermost Maastrichtian sediments and volcanic rocks of the Batain basin, along with fragments of Indian Ocean floor (eastern ophiolites), were obducted northwestward onto the northeastern margin of Oman. Palaeogene neo-autochtonous sedimentary rocks subsequently covered the nappe pile. Tertiary extensional tectonics related to Red Sea rifting in the Late Eocene was followed by Miocene shortening, associated with the collision of Arabia and Eurasia and the formation of the Oman Mountains.

An analysis of 1168 modern soil profiles from the U.S. Natural Resources Conservation Service yields no correlation between mean annual precipitation and depth to the top of the carbonate horizon (r(super 2) = 0.03; p < 0.001). Parent material and soil texture both play negligible roles in this regression. When combined with similar published studies (n = 1481), r(super 2) improves slightly (r(super 2) = 0.31; p < 0.001). Caution is therefore advised in using this or any previously published regression for inferring paleoprecipitation from paleosols. However, in the combined data set, carbonate horizon-bearing soils correlate with a mean annual precipitation of < 760 mm (p < 0.05). Thus the presence vs. absence of pedogenic calcium carbonate is a good indicator of paleoprecipitation above or below this value.

Comparison of the aeromagnetic signatures and geology of southeastern Australia and northern Victoria Land, Antarctica, with similar data from ancient subduction zones in California and Japan, provides a framework for reinterpretation of the plate tectonic setting of the Pacific margin of early Paleozoic Gondwana. In our model, the plutons in the Glenelg (southeastern Australia) and Wilson (northern Victoria Land) zones formed the roots of continental margin magmatic arcs. Eastward shifting of arc magmatism resulted in the Stavely (southeastern Australia) and Bowers (northern Victoria Land) volcanic eruptions onto oceanic forearc crust. The turbidites in the Stawell (southeastern Australia) and Robertson Bay (northern Victoria Land zones) shed from the Glenelg and Wilson zones, respectively, were deposited along the trench and onto the subducting oceanic plate. The margin was subsequently truncated by thrust faults and uplifted during the Delamerian and Ross orogenies, leading to the present-day aeromagnetic signatures.

The authors discuss current magmatic events in the Abbott and Vegetation Units of Antarctica, focusing on the units' unrelated felsic and mafic magma activities. Research indicates that tectonic framework changes occurred during the time of magma accumulation.

Oliverian Magma Series gneisses (442-454 Ma) in the cores of domes in southwestern New Hampshire have an igneous mineralogy that crystallized at pressures (P) of 9-11 kbar and temperatures (T) of 650-775 [degrees] C, whereas the cover (Ammonoosuc Volcanics) has the same formation age (453 [+ or -] 2 Ma) yet is clearly extrusive. A significant crustal section, [approximately]30 km thick, must have originally separated the two units, a recognition that demands tectonic reinterpretation of this classic orogen. Acadian age (ca. 400 Ma) metamorphism at P [approximately]4-6 kbar, T [greater than or equal to] 625 [degrees] C is well documented in the cover, but the absence of expected diffusional reequilibration in Oliverian garnets indicates that they never exceeded [approximately]550 [degrees] C after formation. Juxtaposition of the Oliverian Magma Series gneisses and their cover must have occurred after the cover had cooled below 550 [degrees] C, and was likely via either (neo-)Acadian or Alleghanian thrusting.

Research is presented on paleoceanographic discoveries on corals, their different varieties and their specific mesenterial plans. Other topics include the ecology of ancient corals, growth rates and sizes, and distribution.

The Palaeozoic Uralian orogen formed by accretion of island arcs and microcontinents along the eastern margin ou the East European platform. In the middle Urals, a promontory of the East European platform, the Ufaley Complex experienced eclogite facies conditions followed by an amphibolite facies overprint. The Verkniy Ufaley intrusion crosscuts the amphibolite facies foliation in the East Ufaley Complex and thus postdates the two metamorphic events. A concordant U-Pb age ou 316 +/- 1 Ma obtained on magmatic titanite dates the intrusion ou the pluton and provides a minimum age for subduction and subsequent amphibolite facies metamorphism of the East European continental margin. Zircon yields discordant age data that reflect the involvement of Proterozoic crustal sources.

Dating of lower Paleozoic cherts is now possible through advancements in radiolarian biostratigraphy, permitting greater refinement of structural and stratigraphic models than has previously been possible. A detailed study of the type section of the Ordovician Vinini Formation, Vinini Creek, Roberts Mountains allochthon, Nevada, has yielded anomalously young Devonian ages. These ages were unanticipated and indicate that structural imbrication exists in a classic and previously well dated section of basinal strata. Previous ages of cherts were inferred from their stratigraphic position relative to graptolite-bearing shales. New mapping and biostratigraphy reveal considerable structural interleaving of Ordovician and Devonian strata within the allochthon, and many of the cherts appear to have structural bases. The Roberts Mountains allochthon, considered to be allochthonous but not far traveled, displays a highly complex structural history, including out of sequence thrusting and/or overprinting by later contractional deformation having a similar transport direction. This deformation was previously unrecognized because of the lack of overlap sequences in critical areas and the paucity of internal a;;e control. Because the Roberts Mountains allochthon is not considered to be exotic, but rather has undergone only a modest amount of transport this study shows that convergent margins with high degrees of structural imbrication do not require large amounts of transport. A biostratigraphic approach that examines all lithologies, coupled with detailed observations of field relations, is required for the construction of detailed and accurate structure sections in early Paleozoic orogenic belts.

The late Paleozoic is well documented as a time of significant continental glaciation, but the extents of the glaciation and attendant glacioeustasy are not well constrained because precise amplitudes of eustasy are difficult to extract from the stratigraphic record. In this paper, we use preserved relief on ancient subaerial exposure surfaces of large algal bioherms to demonstrate directly that Late Pennsylvanian glacioeustasy reached minimum amplitudes of 80 m and probably exceeded 100 m. Upper Paleozoic algal bioherms accreted predominantly during sea-level falls, but also during sea-level rises and highstands, and were capable of remarkably rapid growth rates. Eustatic amplitudes in excess of 100 m approach amounts documented for the Pleistocene, and place constraints on models for Gondwanan ice volume, climate dynamics, and potential character and magnitude of glacioclimatic fluctuations.

A study on the relationship between climate change and glacioeustatic sea-level fluctuation in the late Paleozoic sedimentary cycles of the western US is evaluated. Three main problems are observed regarding the study's analysis. These are a lack of high time-stratigraphic resolution allowing comparisons of noncontemporary sedimentary cycles, the comparison of cycles with varying temporal scale and limited climatic data available from single sedimentary cycles.

The time of integration of the North and South China blocks has been debated for years. Different reconstructions of the integration seem to yield contrasting results, mostly pointing to either the Paleozoic age or the Late Triassic age. A new model based on the Qinling tectonic evolution is proposed to reconcile conflicting research yields. Studies that have used this model indicate that the gradual drifting away of the South Qinling orogen occurred during the middle to late Paleozoic period.

Research on sea urchin fossils from the Paleozoic era demonstrates distinctive evolutionary trends. These include the shifting of the ambulacral pores, which reduced the strain on the organisms' tube-feet, and an expansion in oral surface width. Other changes involved flattening from the organisms' original globular form and an increase in plate columns.

Tectonically significant postrift metaigneous rocks occur within three genetically distinct cover-rock sequences along a 400 km strike segment of the southeastern margin of Laurentia, in the southern Appalachian western Blue Ridge. These include (1) Neoproterozoic rift facies rocks, (2) lower Paleozoic drift facies rocks, and (3) unconformably overlying postdrift Paleozoic successor basin sequences. This region is divisible into two along-strike, ensialic, continental margin volcanic belts, separated by a probable Neoproterozoic transfer fault. To the northeast, igneous rocks are intrusive into sequences 1 and 2 above, whereas in the overlying successor basins on both sides of the transfer boundary, they occur predominantly as eruptive rocks. These igneous rocks can be separated into several suites that are distinct from the Neoproterozoic rift-related igneous rocks, based on stratigraphic position, geographic location, and composition. Mafic dikes and sills intrusive into the rift facies and mafic metavolcanic rocks of the Hillabee Greenstone represent low-K tholeiitic magmatism associated with derivation from a 'depleted' mantle source, whereas most igneous rocks in the northeastern belt exhibit an alkaline basalt affinity. The successor basin sequences associated with the volcanic activity formed above extended and thinned continental crust, near and parallel to the southeastern Laurentian margin. This igneous activity can be constrained broadly between stratigraphic position and age of metamorphism (Middle Ordovician to earliest Mississippian time). Most likely this magmatic activity was associated with a destructive plate boundary during Paleozoic A-type subduction, but was largely decoupled from slab-derived magmatism, being instead more likely associated with backarc or pull-apart basin evolution.

The highly allochthonous Talladega belt in the southernmost Appalachian orogen of Alabama and Georgia represents the most completely preserved outboard fragment of the early Paleozoic Laurentian continental margin in this part of the orogen. Palinspastic restoration indicates that this Alleghanian thrust sheet was originally located at or near this continental margin. The Talladega belt is within a structural recess (Alabama recess) in the orogen, which is interpreted to have originated as a continental promontory during the opening and initial closing of the Iapetus ocean. Because continental promontories protrude oceanward along a continental margin, any significant early deformation of this margin should be recorded within this thrust sheet. Regional geologic mapping has revealed a middle Paleozoic regional unconformity within this belt, and distortion of this unconformity by late Paleozoic regional folding provides for examination of subcrop geometries below the unconformity over a large area ([approximately]640 [km.sup.2]). Retrodeformation of the late Paleozoic folds indicates that only very mild deformation predated the unconformity. The origin of this early deformation is unclear. Possibilities include very mild contractional deformation during the Taconic orogeny, or folding associated with wrench or extensional faulting during Silurian(?)-Devonian Acadian successor-basin formation. If the latter is the case, then no vestiges of Taconic deformation can be found in this outboard fragment of the margin, implying that a major continental promontory at the southwesternmost Laurentian margin may have escaped any significant effects of this orogeny.

Fault-bounded (tectonic) metamorphic complexes assembling the NW Bohemian Massif around the German Continental Deep Drilling (KTB) site are seen to be extremely heterogeneous in tectonic and metamorphic histories. In current models, the different complexes were supposed to reflect a puzzle of small pre-Devonian microplates, and the related collision events supposedly lasted until the Carboniferous. Opposed to these models, it will be shown that all the boundaries among the complexes were formed by detachment, late in a prolonged overall geodynamic history of a thickened crustal bulge, during extensional tectonics and associated thermal events that outlasted the onset of collision in the Silurian/Lower Devonian by about 70-80 Ma. (Micro-)structures, petrological and geochronological data of individual complexes predominantly preserve the late stages rather than the unbroken record of their tectonometamorphic histories. Such partial histories strongly different among individual complexes, depict diverse snapshots taken at different places in the evolving thickened crustal bulge and at different instants in its overall evolution, and do not define different precollisional microplates. Predominantly P-T and deformation episodes after terrane juxtaposition are preserved. This article presents an integrated view of the structural geology, microscopic fabrics, P-T data and geochronology of such diverse metamorphic complexes. This integrated view provides a new understanding of (1) the tectonic evolution during Upper Silurian/Devonian collision of the Gondwana-derived Central European lithosphere with Laurussia, (2) the postaccretionary events that lasted through the Upper Carboniferous and (3), the earlier (Lower Ordovician) metamorphic and magmatic history, which is only locally recorded. Metamorphic complexes occupying the structurally highest position (upper tectonic complexes) record Devonian and earlier tectonometamorphic and magmatic events. After the Mid-Devonian, such complexes did not experience any metamorphism. The recorded Devonian events consist of subduction and exhumation of HP-rocks and their exhumation involved thrusting and extensional tectonics. Upper tectonic complexes comprise fragments of both the plate that was subducted in this period and the overriding plate. In the footwall, Carboniferous extension has brought upper tectonic complexes against metamorphic complexes that essentially record Lower and Upper Carboniferous tectonometamorphic and magmatic events (lower tectonic complexes). In the lower tectonic complexes, such events are (1) consecutive extensional stages that created at least three sets of ductile normal detachment systems intersecting each other, and various associated thermal pulses, as well as (2) predetachment events that are only recorded as petrologic and structural relics transposed during extension. Inferred as predetachment events are crustal subduction as well as stacking that outlasted thrusting and exhumation of the upper tectonic complexes. In the deeper portion of the thickened crustal bulge represented by the lower tectonic complexes, spatial variations of P-T-t-d histories during decompression occurred as a result of continued differential exhumation on the three sets of detachment systems, and also from various thermal pulses that have affected different parts of this section during progressive shearing and exhumation to various degrees. Whereas the lower tectonic complexes of the Erzgebirge Gneiss Dome preserve the record of a Lower Carboniferous history of HP-metamorphism and crustal thickening followed by extension, in those of the Oberpfalz region (KTB site), a major Upper Carboniferous thermal pulse mostly erased the pre-Upper Carboniferous strain fabrics and metamorphic record. In the Oberpfalz region, ongoing extension emplaced mid-crustal rocks that pervasively equilibrated in the Upper Carboniferous at high temperatures and low pressures (low P/T ratio) against rocks not exposed to high temperatures at that time. In summary, a prolonged postaccretionary history concealed large-scale structural relationships linked to crustal subduction and thickening associated with former juxtaposition of Gondwana lithosphere to Laurussia. Polyphase crustal extension and strike slip created the variety of different metamorphic tectonic complexes observed in the NW Bohemian Massif. Keywords: Ordovician-Carboniferous; Europe; Variscan orogeny; tectonometamorphic evolution; extension tectonics; microfabrics

The middle to late Paleozoic thermal history of the southern Norwegian crust was studied using K-feldspar thermochronology and geologic constraints. It was observed that the late Paleozoic period was characterized by a cooling phase. This may be attributed to decrease in the base level and the rise in the rate of erosional denudation around the margin of southern Norway due to rifting.

We use structural and petrologic data from a cross section through the high-pressure-low-temperature Maksyutov Complex to develop a new model for its tectonometamorphic evolution. The Maksyutov Complex is located within the southern Urals, the only Paleozoic orogen that apparently preserved its collisional architecture without overprinting by late orogenic extensional deformation. The high-pressure complex constitutes a large antiform in the footwall of the east-dipping Main Uralian fault and is composed of two tectonometamorphic units. The core of the antiform exposes well-preserved eclogites and blueschists in the structurally lower unit I that underwent peak metamorphic conditions of [approximately]17 kbar and [approximately]570 [degrees] C. In contrast, the structurally overlying unit 2 contains lawsonite-bearing assemblages indicating both lower peak pressure (

A structural analysis was conducted on the Carolina-Inner Piedmont terrane boundary to determine the age and kinematics of the central Piedmont suture. Results showed that the Cross Anchor fault is an early Alleghanian thrust, the oldest fault in region and the central Piedmont suture. Moreover, the paleomagnetic data and metamorphic ages in the Carolina terrane suggest its Middle to Late Ordovician accretion to Laurentia.

Paleozoic limestone xenoliths have been recovered from kimberlite pipes that intrude the Archean Canadian Shield. Xenoliths from the Jericho pipe in the central Slave craton are commonly fossiliferous and contain a diverse macrofauna and microfauna, including conodonts. Most of the 21 conodont collections that have been recovered are Middle Devonian in age (late Eifelian to early Givetian, and early to middle Givetian). In general, the fauna is indicative of deposition in shallow- and open-marine environments; a few collections are indicative of slightly restricted shoal-shelf seas. A few low-diversity conodont suites could be pre-Middle Devonian. The nearest similar Paleozoic rocks are more than 400 km to the southwest of the Jericho pipe in the foothills of the Mackenzie Mountains. The Jericho limestone xenoliths provide the only solid evidence that shallow Middle Devonian seas inundated the now-exposed Slave craton of the Canadian Shield.

U-Pb ages of paleosol samples from cyclothemic sections in the Sacramento Mountains of New Mexico and the Permian basin of West Texas bracket the Pennsylvanian-Permian and Carboniferous-Permian boundaries. Linear interpolation and extrapolation to boundaries are accomplished by using cyclothems as periodic subdivisions. The Carboniferous-Permian boundary is 301 [+ or -] Ma (2[Sigma]), the Pennsylvanian-Permian boundary is 302 [+ or -] 2.4 (2[Sigma]), and the Missourian-Virgilian boundary is 307 [+ or -] 3 Ma (2[Sigma]). These ages are within the uncertainties of recent estimates for the boundaries but are significantly more precise. The average cycle duration for this Upper Pennsylvanian and Lower Permian interval is 143 [+ or -] 64 ka (2[Sigma]), within the uncertainty of the [approximately]100 k.y. cycle that dominated Pleistocene sea-level history. This new estimate, which is much shorter than those published previously, suggests that the Pennsylvanian and Early Permian cyclothems may have been driven in a manner similar to that which caused glacio-eustatic cycles of the Pleistocene.

The collision of the Sino-Korean and Yangtze blocks to form a significant part of China is recorded in the Qinling, Tongbai, and Dabie Mountains. Radiometric ages of the ultrahigh-pressure metamorphic rocks in the South Qinling orogenic belt suggest that subduction and collision took place during the Triassic Period. Our new 40Ar/39Ar geochronology of units in the North Qinling orogenic belt confirms that high-grade metamorphism and deformation took place also during the Silurian-Devonian and Carboniferous Periods. These results imply that the amalgamation of eastern China was a multistage process extending over at least 200 m.y.

The Estudio Sismico de la Corteza Iberica Norte Project involves the examination of the Northwestern Iberian Variscan Belt using an offshore vertical incidence reflection seismic method and on-land wide-angle recording. Two important sedimentary basins were identified in the marine seismic section's shallow part. A low continental crust model also shows that the deepest of the two controversial highly reflective subhorizontal bads observed may be the remnants of a crustal root during the late Paleozoic period.

A spectral analysis was conducted on the Bouguer gravity anomalies in eastern Oklahoma and western central Arkansas. Results show that the crustal thickness of the fold and thrust belt rises from 38 km to 44 km from the western to the eastern Ouachitas. Results also reveal that the thickness in the eastern Ouachitas causes anomalously weak lithosphere and is due to the eastward transition of the Paleozoic continental margin from a rift to a transform segment.

A palaeomagnetic study was carried out in the Silurian-Devonian clastic sedimentary rocks of the Sierra Grande Formation, exposed in northeastern Patagonia (41.6 [degrees] S, 65.3 [degrees] W). Thirteen sites (n = 88) were located on opposite limbs of a syncline-anticline structure. Stepwise thermal demagnetization permitted the identification of a very stable magnetic component of reversed polarity carried by hematite. Stepwise performance of the fold test yielded negative results both in situ and after 100% bedding correction, but positive after partial unfolding (19%). This indicates a syntectonic origin for the isolated magnetization. A pole position was computed for the partially (19%) corrected remanence: SG3: 77.3 [degrees] S, 310.7 [degrees] E, [Delta] p = 7.7 [degrees], [Delta]m = 6.6 [degrees], N = 13. Its position is coincident with late Early to Late Permian palaeomagnetic poles from South America, suggesting that age for the previously undated folding of the Sierra Grande sequence and therefore for the main tectonic event that affected the northern boundary of Patagonia. Palaeozoic palaeomagnetic poles from Patagonia obtained to date agree with those from Gondwana of Devonian or younger age, suggesting that Patagonia did not undergo important displacements relative to South America since those times. This and the Permian age of deformation determined in this study invalidates tectonic models involving collision of a far-travelled Patagonia with Gondwana in the mid- or Late Palaeozoic. Keywords: Patagonia, Palaeozoic, Gondwana, palaeomagnetism.

The Vendian-Silurian succession from a series of boreholes in northeast Germany has been petrographically and geochemically investigated. Evidence suggests that the more northerly Vendian and Cambrian succession was deposited on a craton which became increasingly unstable in Ordovician times. Similarly, the Ordovician-age succession deposited in the Rugen area indicates a strongly active continental margin tectonic setting for the same period. By Silurian times the region was once more relatively tectonically quiescent. Although complete closure of the Tornquist Sea was not complete until latest Silurian times, the major changes in tectonic regime in the Eastern Avalonia/Baltica area recorded from the Ordovician suggest that a significant degree of closure occurred during this time.

A systematic survey of 1863 papers on macrobenthic assemblages reveals that an average of 21% of published Paleozoic papers concern silicified fossils, but that average drops to just 4% for post-Paleozoic papers. During the Paleozoic, silicified fossil occurrences do not significantly correlate with the amount of shelf chert, outcrop area, time, duration of geologic intervals, or carbonate rock volume. This substantial drop in numbers of silicified fossils coincides temporally with increased importance of aragonite faunas following the end-Permian extinctions. However, qualitative measurements of secular changes in abundance and diversity of siliceous sponges are consistent not only with the post-Paleozoic decline in fossil silicification, but also with fluctuations in the amount of silicified fossils throughout the Paleozoic. The facies distribution of silicified fossils in the Permian of West Texas also suggests that the distribution of silicified fossils may reflect the occurrence of siliceous sponges. The decline in silicified fossils after the Permian may be related to a concomitant rise in offshore bedded chert deposition and movement of the locus of biogenic silica formation from nearshore to offshore regions beginning in the Triassic, rather than with the expansion of diatoms in the Cretaceous.