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The Mount Meager volcanic complex (MMVC) is one of the eight major calc-alkaline volcanic centres within the Garibaldi Volcanic Belt, Canada. MMVC volcanism spans ~2 Ma and has been mainly intermediate to felsic in composition. However, small-volume mafic centres are located around the periphery of the Mount Meager massif and have been collectively referred to as the Mosaic Assemblage or Mount Meager basalts. Here, we present new [.sup.40A]r/[.sup.39A]r ages and expanded chemical datasets for the MMVC mafic rocks. We show that mafic eruptive ages are both older and longer-lived than previously interpreted, spanning the last ~450 ka, and occurring in four episodes at ~440, 200,106, and 17 ka. We also found that chemical signatures for the MMVC mafic rocks have evolved across the four periods, fluctuating from 'OIB'-like melt characteristics to more typical slabinfluenced, calc-alkaline, before returning to 'OIB'-like in the youngest phase. These findings provide the first evidence of a temporal-chemical evolution of melt sourcing for the Garibaldi belt volcanism. Lastly, field mapping has identified edifices and deposits that are glaciovolcanic in origin (vs. nonglaciovolcanic), which were used in conjunction with our new [.sup.40A]r/[.sup.39A]r age estimates to document the presence or absence of Coast Mountain sectors of earlier Cordilleran ice sheets in southwest British Columbia over the last 500 ka. Key words: Mount Meager, glaciovolcanism, geochronometry, isotope-geochemistry, ice-sheet models, 1. Introduction The Garibaldi Volcanic Belt (GVB) is ~375 km long, northern extension of the Cascade volcanic arc, stretching from Glacier Peak, Washington, USA, to Silverthrone, British Columbia, Canada. The [...]

Based on the study of cores, thin sections, and outcrops, the sedimentary facies of the lower Cambrian carbonate rocks in the northern Tarim Basin can be divided into four types: restricted platform, open platform, ramp, and basin. Based on the lithologic analysis of thin sections, two-dimensional seismic data interpretation, and an isopach map of the lower Cambrian Xiaoerbulake Formation in the study area, seven sedimentary facies of carbonate rocks were identified, including inner platform depression, shoal, intershoal sea, platform margin, gypsum salt lake, ramp, and basin. The depositional model of the lower Cambrian Xiaoerbulake Formation in the northern Tarim Basin is constructed based on this integrated research. The topset, foreset, and bottomset of oblique progradational reflections are interpreted as the platform margin beach, ramp, and basin environments, respectively. The thicker area with micritic dolomite as the dominant lithology is interpreted as a platform depression. The low-amplitude hummocky reflections are interpreted as shoals that consist of a variety of granular dolomite and algal dolomite. The thinner uplifted area with gypsum and dolomite present in cores is interpreted as a restricted platform with a gypsiferous dolomite tidal flat or lake environment. Well LT1, which was drilled recently in the platform margin and ramp region, as indicated by seismic progradational clinoform reflections, has produced high yields of oil and gas. Supported by the above research results, the map of the lithofacies and paleogeography of the Xiaoerbulake Formation in the northern Tarim Basin was recompiled. Key words: Tarim Basin, lower Cambrian, Xiaoerbulake Formation, lithofacies and paleogeography, seismic facies. A la lumiere de l'etude de carottes, de lames minces et d'affleurements, les facies sedimentaires des roches carbonatees du Cambrien inferieur dans le nord du bassin de Tarim peuvent etre subdivises en quatre types, a savoir, les facies de plateforme restreinte, de plateforme ouverte, de talus et de bassin. A la lumiere de l'analyse lithologique de lames minces, de l'interpretation de donnees de sismique bidimensionnelle et d'une carte d'isopaques de la Formation de Xiaoerbulake du Cambrien inferieur dans la region a l'etude, sept facies sedimentaires de roches carbonatees ont ete etablis, soit les facies de depression de plateforme interne, de basse, de mer inter-basse, de marge de plateforme, de lac de sel de gypse, de talus et de bassin. Le modele de depot de la Formation de Xiaoerbulake dans le nord du bassin de Tarim est etabli sur la base de cette recherche integree. La couche sommitale, la couche frontale et la couche basale des reflexions progradantes obliques sont interpretees comme etant les milieux de plage de marge de plateforme, de talus et de bassins, respectivement. La zone plus epaisse dans laquelle de la dolomie micritique constitue l'unite dominante est interpretee comme representant une depression de plateforme. Les reflexions bosselees de faible amplitude sont interpretees comme etant des basses constituees variablement de dolomie granulaire et de dolomie algale. La zone soulevee plus mince dont les carottes contiennent du gypse et de la dolomie est interpretee comme etant une plateforme restreinte caracterisee par un milieu de platin ou de lac a dolomie gypsifere. Le puits LT1 fore recemment dans la region de marge de plateforme et de talus, comme l'indiquent les reflexions clinoformes progradantes, a produit de bons rendements petroliers et gaziers. La carte des lithofacies et de la paleogeographie de la Formation de Xiaoerbulake dans le bassin de Tarim a ete recompilee a la lumiere des resultats de recherche susmentionnes. [Traduit par la Redaction] Mots-cles : bassin de Tarim, Cambrien inferieur, Formation de Xiaoerbulake, lithofacies et paleogeographie, facies sismique., Introduction The Cambrian dolomitic rocks in the Tarim Basin have a thickness of more than 1 km and a distribution area of 410 000 [km.sup.2] (Du and Pan 2016). In [...]

Middle to Upper Devonian strata of the Franklinian Basin in the Canadian Arctic contain a rich record of Phanerozoic tectonic events along the northern margin of Laurentia. We report detrital thermochronometric zircon (U-Th)/He ages (ZHe; number of aliquots, n = 72) and apatite (U-Th)/He ages (AHe; n = 38) from these Paleozoic strata in an effort to better understand the sediment source regions and the exhumation history of the basin. Detrital ZHe ages are older than corresponding stratigraphic ages and were not reset during subsequent burial, thus constraining both maximum burial depths ( Les strates du Devonien moyen a superieur dans le bassin franklinien de l'Arctique canadien contiennent un enregistrement important d'evenements tectoniques (Phanerozoique) le long de la bordure nord de la Laurentie. Nous rapportons des ages thermochronometriques (U-Th) sur des zircons detritiques (ZHe; n = 72) et a partir d'apatites (U-Th)/He (Ahe; n = 38) de ces strates paleozoiques ain de mieux comprendre les regions sources des sediments et l'historique de l'exhumation du bassin. Les ages ZHe detritiques sont plus anciens que les ages stratigraphiques correspondants et ils n'ont pas ete rajeunis durant l'enfouissement subsequent, limitant ainsi les profondeurs maximales d'enfouissement (, Introduction The geologic record of the Canadian Arctic Islands provides important insights into the tectonic evolution of the northern Laurentian margin as well as the development of the adjacent Amerasian [...]

The western quarter of North America consists of accreted terranes--crustal blocks added over the past 200 million years--but the reason for this is unclear. The widely accepted explanation posits that the oceanic Farallon plate acted as a conveyor belt, sweeping terranes into the continental margin while subducting under it. Here we show that this hypothesis, which fails to explain many terrane complexities, is also inconsistent with new tomographic images of lower-mantle slabs, and with their locations relative to plate reconstructions. We offer a reinterpretation of North American palaeogeography and test it quantitatively: collision events are clearly recorded by slab geometry, and can be time calibrated and reconciled with plate reconstructions and surface geology. The seas west of Cretaceous North America must have resembled today's western Pacific, strung with island arcs. All proto-Pacific plates initially subducted into almost stationary, intra-oceanic trenches, and accumulated below as massive vertical slab walls. Above the slabs, long-lived volcanic archipelagos and subduction complexes grew. Crustal accretion occurred when North America overrode the archipelagos, causing major episodes of Cordilleran mountain building., Continents grow through subduction magmatism and collision of arcs and other buoyant crustal fragments at their margins. Poorly understood, such collisions are of broad scientific interest because they cause rapid [...]

We have established a new plate kinematic model of the central and North Atlantic oceans between North America, Africa, Meseta, Iberia, Flemish Cap, and Galicia Bank from Late Triassic to Late Cretaceous to better understand the nature and timing of rifting of Nova Scotia and Morocco conjugate continental margins since Late Triassic. The maps of salt distributions at the Sinemurian-Pliensbachian limit (190 Ma; after salt deposition) and in middle Bajocian (170 Ma) show that an area of the Nova Scotia margin is devoid of allochthonous salt and that an area of similar size located oceanward of the West African Coast Magnetic Anomaly shows salt deposits, suggesting that a portion of the Nova Scotia margin with its overlying salt deposits could have been transferred onto the Moroccan side right after the formation of the conjugate East Coast Magnetic Anomaly and West African Coast Magnetic Anomaly. Seven paleogeographic maps, from Late Triassic to Late Cretaceous, are presented with structural elements and magnetic lineations. They show that the connection between the Central Atlantic and the Tethys, with an aborted rift between Iberia and North America ending in the north against the Flemish Cap--Galicia Bank dam, started to deepen at the end of the first rifting phase (190 Ma ago) after the rupture of the thinned continental crust. It is only during the Early Cretaceous, after the rupture of the Flemish Cap--Galicia Bank dam, that the deep connection around Iberia was finally established between the Central and North Atlantic, the Tethys, and the Bay of Biscay. Nous avons etabli un nouveau modele cinematique de l'ocean atlantique nord et central pour les plaques Amerique du Nord, Afrique, Meseta, Iberie, Bonnet Flamand et Banc de Galice, depuis le Trias tardif jusqu'au Cretace terminal, afin de mieux comprendre la nature et le sequencement de la distension des marges continentales conjuguees de la Nouvelle-Ecosse et du Maroc. Selon les cartes de distribution du sel a la limite du Sinemurien-Pliensbachien (190 Ma; apres la deposition du sel) et au Bajocien moyen (170 Ma), un secteur de la bordure de la Nouvelle-Ecosse n'a pas de sel allochtone et un secteur de dimension semblable situe du cote oceanique de l'anomalie magnetique de la cote ouestafricaine montre des depots de sel, suggerant qu'une portion de la bordure de la Nouvelle-Ecosse, et de ses depots de sel sus-jacents, pourrait avoir ete transferee du cote du Maroc tout de suite apres la formation des anomalies magnetiques conjuguees de la Cote Est et de la Cote Ouest--Africaine. Sept cartes paleogeographiques, du Trias tardif au Cretace terminal, sont presentees avec des elements structuraux et des lineations magnetiques. Elles montrent que la connexion entre l'Atlantique central et la Tethys, avec une distension interrompue se terminant au Nord contre le barrage Bonnet Flamand--Banc de Galice, a commence a s'approfondir a la fin de la premiere phase de distension (il y a 190 Ma) apres la rupture de la croute continentale amincie. Ce n'est que durant le Cretace precoce, apres la rupture du barrage Bonnet Flamand--Banc de Galice, que la connexion profonde autour de la peninsule Iberique a finalement ete etablie entre l'Atlantique Nord et Central, la Tethys et le golfe de Gascogne. [Traduit par la Redaction], Introduction The Gradstein et al. (2004) geologic time scale is used all along this paper. Plate reconstructions in the Central Atlantic have been recently updated from Late Triassic (203 Ma) [...]

New detrital zircon uranium-lead (U-Pb) ages and initial epsilon hafnium ([ζ.sub.Hf(i)]) data from the Devonian clastic succession of the Canadian Arctic Islands refines the provenance of strata within the Franklinian Basin and provides constraints on the geologic evolution of the landmass responsible for the Ellesmerian Orogen. This study contributes more than 500 U-Pb ages and 32 [ζ.sub.Hf(i)] values from the Blackley Formation and the Parry Islands Formation. The Middle Devonian Blackley Formation represents the onset of clastic sedimentation into the Franklinian Basin during the Devonian period. Detrital zircon from two samples yield U-Pb age populations of 380-470, 500-700, 900-2100, and 2550-3000 Ma. The population of 500-700 Ma U-Pb ages indicates a source exotic to the northern Laurentian margin and is attributed to a continental landmass located north of the present Canadian Arctic Islands (often referred to as Crockerland). This is some of the earliest evidence of 500-700 Ma detrital zircon deposition onto the northern Laurentian margin and indicates this northern landmass is at least partially accreted to Laurentia by early-Eifelian time. The Late Devonian Parry Islands Formation is the uppermost succession of Ellesmerian Orogen foreland basin sedimentation in the Franklinian Basin. Detrital zircon from four samples yield U-Pb age populations of 370-450, 470-750, 930-2100, and 2300-3200 Ma. The U-Pb ages suggest the Parry Islands Formation is derived from the northern source terrane (Crockerland) and indicate this landmass contains rocks similar to that of the east Greenland Caledonides, Pearya, and northeastern Baltica. Rim and core U-Pb double dates from the 500-700 Ma detrital zircon population and [ζ.sub.Hf(i)] values from the 380-450, 520-550, and 650-710 Ma detrital zircon populations help constrain magma generation processes within Crockerland and suggest the zircons are derived from a juvenile lithosphere. De nouveaux ages uranium-plomb (U-Pb) sur zircon detritique et des donnees epsilon hafnium initial ([ζ.sub.Hf(i)]) de la succession clastique (Devonien) des iles de l'Arctique precisent la provenance de strates dans le bassin franklinien et encadrent revolution geologique de la masse terrestre responsable de l'orogenese a l'Ellesmerien. La presente etude contribue plus de 500 ages U-Pb et 32 valeurs [ζ.sub.Hf(i)] de la Formation de Blackley et de la Formation de Parry Islands. La Formation de Blackley (Devonien moyen) represente le debut de la sedimentation clastique dans le bassin franklinien durant le Devonien. Des zircons detritiques provenant de deux echantillons ont donne des ages U-Pb de 380-470, 500-700, 900-2100 et 2550-3000 Ma. Les populations des ages U-Pb de 500-700 Ma indiquent une source exotique a la bordure laurentienne nord et cette source serait une masse continentale situee au nord des iles de l'Arctique actuelles (souvent designee en tant que Crockerland). Il s'agit d'une des plus anciennes evidences de deposition de zircon detritique de 500-700 Ma a la bordure laurentienne nord et cela indique que cette masse terrestre nordique a ete accretee, du moins en partie, a la Laurentie des le debut de l'Eifelien. La Formation de Parry Islands (Devonien tardif) constitue la succession au sommet de la sedimentation d'avant-pays de l'orogenese de l'Ellesmerien dans le bassin franklinien. Des zircons detritiques provenant de quatre echantillons ont donne des ages U-Pb de 370-450, 470-750, 930-2100 et 2300-3200 Ma. Les ages U-Pb suggerent que la Formation de Parry Islands soit derivee du terrane source nord (Crockerland) et cela indique que la masse terrestre contenait des roches semblables a celles des Caledonides du Groenland, de Pearya et du nord-est de Baltica. Les dates U-Pb en double de la bordure et du noyau de la population de 500-700 Ma de zircon detritique et les valeurs [ζ.sub.Hf(i)] des populations de zircon detritique 380-450, 520-550 et 650-710 Ma aident aa contenir les processus de generation de magma aa l'interieur de Crockerland et suggerent que les zircons proviennent d'une lithosphere juvenile. [Traduit par la Redaction], Introduction The number of detrital zircon uranium-lead (U-Pb) ages reported from the high Arctic has increased dramatically in recent years (Kuznetsov 2006; Miller et al. 2006,2010; Lorenz et al. 2008; [...]

Palaeontological exploration of the Bonnet Plume Basin in northwestern Yukon Territory, Canada, has revealed a Late Paleocene to Early Eocene macrofloral assemblage from a channel fill deposit. The flora is typified by cosmopolitan taxa and dominated by deciduous angiosperms, with the notable presence of Zizyphoides, Ettingshausenia, and Corylites. Floras with a similar composition are known from Late Cretaceous through Early Eocene deposits in Alaska and the Canadian Arctic Archipelago, where they have been interpreted as evidence for warm, equable temperatures. This collection represents the most diverse known Paleogene plant macrofossil assemblage from the Yukon Territory and helps to expand our knowledge of ancient high-latitude floras. L'exploration paleontologique du bassin de Bonnet Plume, dans le nord-ouest du Yukon (Canada), a revele la presence d'un assemblage macrofloral datant du Paleocene tardif a l'Eocene precoce dans un depot de remplissage de chenal. Cette flore est caracterisee par des taxons cosmopolites et dominee par des angiospermes a feuilles caduques dont, notamment Zizyphoides, Ettingshausenia et Corylites. Des flores de composition semblable sont connues de depots allant du Cretace tardif a l'Eocene precoce de l'Alaska et des iles de l'Arctique canadien, ou leur presence a ete interpretee comme temoignant de temperatures chaudes et relativement uniformes. Cette collection represente l' assemblage de macrofossiles vegetaux paleogenes le plus diversifie du Yukon et contribue a accroitre les connaissances sur les flores anciennes de hautes latitudes. [Traduit par la Redaction], Introduction Fossil floras are some of the best empirical evidence of extreme climate change in the High Arctic and have been recognized as such for over a century (Stopes 1914; [...]

Strata of the Campbellton Formation, nearly 1 km-thick and known for its diverse fossil assemblage of early plants, arthropods, and fish, can be divided into six facies associations: (1) restricted lacustrine, (2) marginal lacustrine, (3) near-shore lacustrine, (4) coastal-deltaic, (5) sandy to gravelly alluvial plain, and (6) gravelly proximal alluvial environments. Lacustrine deposits with restricted circulation, due to depth or stagnation, are fine-grained with preserved organic material. The marginal lacustrine association consists of massive siltstone and very fine sandstone, interbedded with conglomerate. The latter are interpreted to have shed from older volcanic units forming the basin walls. The near-shore lacustrine association is characterized by rippled sandstone with microbialites. Alluvial strata include interbedded imbricate to nonimbricate conglomerate, trough cross-stratified sandstone, and barren to plant-bearing siltstone. Rare exposures of thickly bedded imbricate to weakly imbricated cobble-boulder conglomerate with sandy plant-bearing lenses are interpreted as products of hyperconcentrated debris flows. In the western belt, a braided-fluvial system had paleocurrents flowing WNW. Coastal-deltaic deposits west of the fluvial outcrops, containing aquatic vertebrates and invertebrates, had paleocurrents flowing ESE, suggesting a confined body of fresh or brackish water. In lower parts of the eastern belt, lacustrine facies are prevalent, representing a large open lake. Alluvial facies dominate upper parts of the formation, representing an eastward-flowing axial braided river system, with proximal alluvium shed transversely from the basin margins. Although most strata have a volcanic provenance, only one outcrop in the lacustrine beds shows evidence of active volcanism during deposition of the Campbellton Formation. D'une epaisseur d'environ 1 km, les strates de la Formation de Campbellton sont connues pour ses assemblages diversifies de fossiles d'anciennes plantes, d'arthropodes et de poissons; elles peuvent etre divisees en six associations de facies : (1) lacustre restreinte, (2) lacustre de bordure, (3) lacustre pres d'un rivage, (4) cotier-deltaique, (5) plaine alluviale de sable a gravier et (6) environnements proximaux de gravier alluvionnaire. En raison de la profondeur ou de stagnation, les depots lacustres avec circulation reduite sont a grain fin et contiennent de la matiere organique preservee. L'association lacustre de bordure comprend des siltstones massifs et des gres tres fins, interlites avec des conglomerats. Ces derniers proviendraient d'anciennes unites volcaniques qui forment les parois du bassin. L'association pres du rivage est caracterisee par des gres rides contenant des microbialites. Les strates alluvionnaires comprennent un conglomerat imbrique a non imbrique, des gres de fosse a stratification croisee et des siltstones steriles a contenant des plantes. De rares affleurements de conglomerats imbriques a lits epais a des conglomerats de cailloux a blocs faiblement imbriques avec des lentilles sablonneuses comportant des plantes, sont interpretes en tant que produits de coulees de debris hyperconcentrees. Dans la ceinture ouest, un systeme de ruisseaux anastomoses avait des paleocourants qui s'ecoulaient vers l'ONO. Les depots cotiers-deltaiques a l'ouest des affleurements fluviaux, contenant des vertebres et des invertebres aquatiques, avaient des paleocourants qui s'ecoulaient vers l'ESE, suggerant un plan confine d'eau douce ou saumatre. Dans les parties inferieures de la ceinture orientale, les facies lacustres prevalent, representant un vaste lac ouvert. Des facies alluviaux dominent les parties superieures de la formation, representant un systeme axial de rivieres anastomosees coulant vers l'est, avec des alluvions proximales qui tombent transversalement aux bordures du bassin. Bien que la plupart des strates proviennent de volcans, un affleurement dans les lits lacustres montre des evidences de volcanisme actif pendant la deposition de la Formation de Campbellton. [Traduit par la Redaction], Introduction On the southern shore of the Restigouche River in New Brunswick, Canada, near the head of Chaleur Bay, a narrow belt of the Emsian to Eifelian Campbellton Formation is [...]

Local gold concentrations are found in laterally extensive pyrite-bearing, framework-supported, cobble and boulder conglomerates in the basal 30 m of the Mississagi Formation in the south eastern part of the Huronian outcrop belt. These were deposited as part of a valley-fill succession, in shallow gravel-bed braided rivers with local hyperconcentrated flows. The basal contact with underlying Archean psammites is typically highly irregular and shows no obvious sign of weathering suggesting that deposition took place soon after retreat of the glaciers responsible for deposition of the Ramsey Lake Formation. Highest gold concentrations are associated with moderately well-sorted medium to large pebble conglomerate that show some signs of reworking during low flow events. Depositional elements are typically lenticular and of limited lateral extent. Unlike the older pyritic quartz-pebble conglomerates at the base of the Matinenda Formation in the Elliot Lake and Blind River areas, these conglomerates contain no uraninite and are polymict with material derived from a highly restricted catchment area with marked local and regional topographic relief. Porous detrital allogenic pyrite and euhedral post-depositional pyrite have overlapping, generally positive [δ.sup.34]S values, indicating a closed system during diagenesis and metamorphism. The presence of biotite-enriched rims on many of the metavolcanic and metasedimentary clasts in the conglomerates suggests that gold was partly leached from the allogenic pyrite grains at the peak of the Penokean Orogeny at 1.85-1.5 Ga. The potential source of the Au-bearing detrital allogenic pyrite appears to be an as yet undiscovered Archean volcanic-hosted massive sulfide (VHMS) deposit located 1 to 8 km north of the deposit. Des concentrations d'or sporadiques se trouvent dans des orthoconglomerats de blocs et de galets, a forte extension laterale et contenant de la pyrite, dans les 30 m inferieurs de la Formation de Mississagi dans la partie sud-est de la ceinture d'affleurements huronienne. Ces concentrations ont ete deposees en tant que partie d'une suite de remplissage de vallee, dans des lits de riviere anastomoses a faible profondeur avec des debits par endroits hyperconcentres. Le contact a la base avec les psammites archeennes est typiquement hautement irregulier et ne montre aucun signe evident de meteorisation, suggerant que la deposition ait eu lieu peu de temps apres le retrait des glaciers responsables de la deposition de la Formation Ramsey Lake. Les concentrations d'or les plus elevees sont associees a des conglomerats moyennement bien tries de gros et de moyens cailloux qui montrent quelques signes de remaniement durant les episodes de faible debit. Les elements de sedimentation sont typiquement lenticulaires et d'etendue laterale limitee. A la difference des conglomerats de cailloux de quartz pyritique plus anciens a la base de la Formation de Matinenda dans les secteurs du lac Elliot et de la riviere Blind, ces conglomerats ne contiennent aucune uraninite et ils sont polymictiques, contenant du materiel derive d'un bassin hydrologique grandement restreint et presentant un relief topographique local et regional appreciable. La pyrite poreuse detritique allogene et la pyrite automorphe, post-sedimentaire, ont des valeurs [δ.sup.34]S generalement positives, indiquant un systeme ferme durant la diagenese et le metamorphisme. La presence de bordures enrichies de biotite sur plusieurs clastes metavolcaniques et metasedimentaires dans les conglomerats suggere une lixiviation partielle de l'or des grains de pyrite allogene au maximum de l'orogenese du Penokeen il y a 1,85-1,5 Ga. La source potentielle de la pyrite detritique allogene aurifere semble etre un gisement archeen de sulfures massifs dans des roches volcaniques (VHMS), pas encore decouvert, situe a une distance de 1 a 8 km au nord du gisement. [Traduit par la Redaction], Introduction Recent exploration in Clement and Pardo Townships by Endurance Gold Corporation (Vancouver, BC), on the southern margin of the Cobalt Plain (Figs. 1 and 2) has identified significant concentrations [...]

We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Nino--Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical mode[ simulations of orbital forcing into a La Nina--like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Nino--like (warm) conditions, in apparent agreement with the theoretical 'ocean dynamical thermostat' response of ENSO to exogenous radiative forcing. 10.1126/science.1194887

A comparison was performed of solar activity and terrestrial temperature records, both derived from tree rings (i.e., without dating uncertainties), with identification of detailed and highly quantified time- and time-scale-dependent characteristics of solar forcing on climate through the current interglacial in the context of oceanic variability. The tree-ring-derived temperature record from high latitudes of Europe (Lapland) exhibits persistent annual-to-millennial--scale variations, with multidecadal to multicentennial periodicities reminiscent of the Sun's periodicities. At millennial scales, cool temperatures coincided with large-scale glacial maxima. Moreover, millennial and bimillennial modes of climate variability were correlative with variations in sunspot numbers on similar scales, with near-century and near-zero lags, respectively. Although they were subtle in amplitude, the sub-Milankovitch--scale changes in the reception of the Sun's energy could thus suffice to noticeably modulate interglacial climate variations. The relative significance of timescale-dependent, Sun-climate linkages has likely varied during the mid and late Holocene times, respectively. Thus, the warmer and cooler paleotemperatures during the Medieval Climate Anomaly and Little Ice Age were better explained by solar variations on a millennial rather than bimillennial scale. The observed variations may have occurred in association with internal climate amplification (likely, thermohaline circulation and El Nino--Southern Oscillation activity). The near-centennial delay in climate in responding to sunspots indicates that the Sun's in fluence on climate arising from the current episode of high sunspot numbers may not yet have manifested itself fully in climate trends. If neglected in climate models, this lag could cause an underestimation of twenty-first-century warming trends. doi: 10.1130/B30088.1

Deformation along the northern edge of the westward-moving Anatolian plate is concentrated along the North Anatolian fault. This northward-arching fault extends from the Karliova triple junction in the east, ~1500 km into the Aegean Sea in the west. A sequence of twentieth-century earthquakes ruptured the fault, displaying a spatiotemporal pattern consistent with a stress triggering mechanism. In 1943, the [M.sub.w] 7.6 Tosya earthquake ruptured a 280-km-long segment near the center of the fault. Four paleoseismic investigations have previously investigated this segment, and the present study was conducted near its center, in an ~180-km-long gap between existing studies. A paleoseismic trench revealed a sequence of eight sediment packages abutting a highly developed shear zone. Each of the packages consists of a fine-grained layer overlying a coarse-grained layer. Based on correlation between the age of the base of the coarse-grained layers and existing earthquake records, we infer that the coarse-grained layers were deposited in response to earthquakes because of increased erosion on an adjacent steep slope. The most recent event horizon may correlate to the historical 529 A.D. earthquake. Timing of six older earthquakes is constrained to (2s): 23 B.C.-103 A.D., 609-185 B.C., 971-814 B.C., 1227-968 B.C., 2050-1777 B.C., and 2556-2235 B.C., which correspond to a summed interevent time of 97-912 yr (2s). The earthquake record is relict because the local stream network was incised ca. 1000 A.D., isolating the trench site from its sediment source. A stream near the trench was subsequently offset by 23.5 [+ or -] 1.5 m, yielding a right-lateral slip rate of 21.4-25.6 mm/yr and suggesting that the 1943 rupture caused an uncharacteristically small offset. doi: 10.1130/B30081.1

A non--North American provenance for the lower Belt Supergroup of North America has been used to support various pre-Rodinian paleogeographic reconstructions. Unlike the lower Belt Supergroup, most upper Belt Supergroup provenance studies have inferred Laurentian sediment sources. We test this hypothesis by analyzing U-Pb and Lu-Hf isotopes on detrital zircons, and whole-rock Nd isotopes from the Missoula (upper Belt Supergroup) and Lemhi Groups, and comparing to possible Laurentian sources. Detrital zircons from 11 sandstones analyzed show dominant ages between 1680 and 1820 Ma. These zircons are predominantly magmatic in paragenesis. Belt Supergroup--aged (1400-1470 Ma) and 2400-2700 Ma populations represent minor components. Lu-Hf isotopic analyses for 1675-1780 Ma Missoula Group and Lemhi Group detrital zircons range from [epsilon]Hf(i) +9 to -12 and +8 and -7, respectively. Belt Supergroup--aged grains from the Bonner Formation, Missoula Group, have [epsilon]Hf(i) values between +5 and -9, exceeding coeval ranges from the Mojave and Yavapai terranes [[epsilon]Hf(i) between +5 and 0]. Whole-rock Nd isotopes from Lemhi Group argillites yield a range in ENd(1400) between +1.1 and -5.9. Immature feldspathic sediment, nearly unimodal detrital zircon spectra, and dissimilar Belt Supergroup--aged zircon Hf signatures suggest that distal portions of the Yavapai and Mojave terranes intruded by A-type magmas were not the source for the Missoula and Lemhi Groups. Instead, a slightly modified Mesoproterozoic proto-SWEAT (southwestern United States and East Antarctica) model can best account for the sedimentologic and isotopic characteristics of the Missoula and Lemhi Groups. An alternative model with a source from southeastern Siberia and the Okhotsk Massif is less preferred. doi: 10.1130/G31194.1

* Premise of the study: Around the world, tropical glaciers and ice caps are retreating at unprecedented rates because of climate change. In at least one location, along the margin of the Quelccaya Ice Cap in southeastern Peru, ancient plant remains have been continually uncovered since 2002. We used genetic analysis to identify plants that existed at these sites during the midHolocene. * Methods: We examined remains between 4576 and 5222 yr old, using PCR amplification, cloning, and sequencing of a fragment of the chloroplast trnL intron. We then matched these sequences to sequences in GenBank. * Key results: We found evidence of at least five taxa characteristic of wetlands, which occur primarily at lower elevations in the region today. * Conclusions: A diverse community most likely existed at these locations the last time they were ice-free and thus has the potential to reestablish with time. This is the first genetic analysis of vegetation uncovered by receding glacial ice, and it may become one of many as ancient plant materials are newly uncovered in a changing climate. Key words: ancient DNA; Andes; bofedal; Holocene; puna. doi: 10.3732/ajb.1000058

U-Pb detrital zircon analyses provide a new maximum depositional age constraint on the Uinta Mountain Group (UMG) and correlative Big Cottonwood Formation (BCF) of Utah, and significantly enhance our insights on the mid-Neoproterozoic paleogeographic and tectonic setting of western Laurentia. A sandstone interval of the Outlaw Trail formation with a youngest population (n = 4) of detrital zircons, from a sampling of 128 detrital zircon grains, yields a concordia age of 766 [+ or -] 5 Ma. This defines a maximum age for deposition of the lower-middle Uinta Mountain Group in the eastern Uinta Mountains and indicates that the group is no older than middle Neoproterozoic in age (i.e., Cryogenian). These data support a long-proposed correlation with the Chuar Group of Grand Canyon (youngest age 742 Ma [+ or -] 6 Ma), which, like the Uinta Mountain Group and Big Cottonwood Formation, records nonmagmatic intracratonic extension. This suggests a ~742 to [less than or equal to]766 Ma extensional phase in Utah and Arizona that preceded the regional rift episode (~670-720 Ma), which led to development of the Cordilleran passive margin. This is likely an intracratonic response to an early rift phase of Rodinia. Further, because the Chuar Group and the Uinta Mountain Group-Big Cottonwood Formation strata record intracratonic marine deposition, this correlation suggests a regional ~740-770 Ma transgression onto western Laurentia. The detrital grain-age distributions from 12 samples include the following grain-age populations and interpreted provenance: 2.5-2.7 Ga (late Archean southern Wyoming province); 1.6-1.8 Ga (Paleoproterozoic Yavapai province); 1.5-1.6 Ga (Early Mesoproterozoic North American magmatic gap), 1.4-1.45 Ga (Colorado province A-type granite-rhyolite belt); 0.93-1.2 Ga (eastern Grenvillian orogen); and mid-Neoproterozoic volcanic grains (766 Ma). Sediment was transported by: (1) a major longitudinal west-flowing river system tapping the Grenville orogen, (2) local south-flowing drainages off the southern Wyoming craton, and (3) northerly and westerly flowing marine currents. The Uinta Mountain Group river system was one of several major transcontinental drainages that delivered Grenvillian zircon grains to the proto--Pacific Ocean. We propose that this river system ultimately supplied sediment to peri-Gondwanan margins along the proto-Pacific to Antarctica, Australia, and South America, providing an alternative source for explaining the problematic provenance of Grenvillian grains in these areas. doi: 10.1130/B30094.1

The glaciomarine sedimentary record of the fjord head (Collins Harbor) in Maxwell Bay, South Shetland Islands (West Antarctica), a large marine calving embayment, contains repeating couplets of organic-rich massive diamicton and organic-poor stratified diamicton. The massive diamicton is characterized by high total organic carbon (TOC) content and carbon to nitrogen (C/N) ratios and was deposited in a cold climate regime by iceberg-rafted sedimentation from coastal fast ice in which algal plants, as well as gravels, were entrained. The stratified diamicton is characterized by low TOC content and C/N ratios and was formed in a warmer climate regime when the flux of icebergs was suppressed, but turbid meltwater discharge continued to produce lamination. When the meltwater discharge decreased in cold climatic conditions, and resultant phytoplankton productivity was reduced due to the increased sea-ice coverage, ice rafting from shorefast sea ice might have played a major role in entraining benthic algae, as well as loads of sand and gravel, along the coastal area, resulting in an increased C/N ratio and gravel content in the massive diamicton. Accelerator mass spectrometry (AMS) radiocarbon analyses conducted on well-preserved calcite shells were used to construct a chronology for the past 3000 years. Fluctuations in TOC are recorded (approximately four cycles over this time period), with the average duration of a cooling cycle being ~500 years. These cycles may be correlative with the high-frequency (550 yr) variability in reduced Circumpolar Deep Water (CDW) on the West Antarctic Peninsula shelf, because a decrease in CDW may be related to reduced deep water production in the North Atlantic during colder periods, as demonstrated for glacial intervals throughout the Pleistocene. doi: 10.1130/B30178.1

The geographical location of the Lhasa terrane in the Permian remains a subject of debate. The recognition of the Permian basalts in the Tethyan Himalaya and the Permian volcanic rocks in the Lhasa terrane in southern Tibet together with the geochemistry of these rocks offer some new insights. The Permian basalts in the Tethyan Himalaya show a geochemical affinity with tholeiitic continental flood basalts, and are interpreted to have formed in an extensional setting. The new geochemical data and the geographical distribution of these basalts indicate that they probably represent the easternmost extent of the Panjal continental flood basalt province. All of the Permian basalts in the Lhasa terrane show a calc-alkaline, high-alumina basalt affinity, with significant negative Nb-Ta-Ti anomalies. These geochemical features, combined with the recent documentation of the Permian Songdo eclogite and sedimentological observations, indicate the existence of a subduction system beneath the central Lhasa subterrane in the Permian. The presence of both extension- and arc-type magmatism of Permian age in present-day southern Tibet is inconsistent with the general view that the Lhasa terrane did not rift away from the northern margin of the Greater India until the Late Permian or Triassic. Instead, we suggest that the central Lhasa subterrane may have been a microcontinent isolated in the Paleo-Tethyan Ocean basin, at least during the Carboniferous-Middle Permian time. doi: 10.1130/B30062.1

The Coastal Range in eastern Taiwan is characterized by rapid uplift at a rate of about 5 mm [yr-sup.1] because of active arc-continent collision since the Mio-Pliocene. The Coastal Range includes three main levels of Holocene marine terraces, labeled the first, second, and third levels descending to the coast. The soils that have developed on the terraces provide a chronosequence for pedogenic studies. Thirteen soil pedons formed from conglomerate associated with tuff were sampled along three transects in the central and southern part of the eastern coast of Taiwan near the localities of Chang-Bin, Cheng-Gong, and Du-Lan. The soils of the oldest terrace (first level) are mainly Typic Hapluderts with one Typic Hapludoll; the soils of the intermediate terrace (second level) are Vertic or Typic Hapludolls; and the soils of the youngest terrace (third level) are Typic Udipsamments. The degree of development of these soils can be determined from horizon index (HI), weighted profile development index (WPDI), weighted mean profile (WMP) clay, WMP silt, WMP sand, and WMP cation exchange capacity with correlation coefficients (r) >0.6 by linear or logarithmic functions. Comparisons of the chronofunctions based on WMP clay data in subtropical and Mediterranean climates suggest that climatic conditions not only control weathering intensity but also influence rates of soil development. The pedogenic evidence in this study supports the correlation of terraces suggested by previous geomorphic and tectonic studies. The anomalous, relatively weaker degree of soil development on the oldest terrace at Du-Lan supports the conclusion that uplift rates in the Du-Lan area are greater than at Chang-Bin and Cheng-Gong. Abbreviations: cal., calibrated; HI, horizon index; OC, organic carbon; WMP, weighted mean profile; WPDI, weighted profile development index; XRD, x-ray diffraction. doi: 10.2136/sssaj2009.0276

Hurricane magnitude and frequency have been linked to numerous mechanisms, including the steady rise in annual sea-surface temperatures, El Nino--Southern Oscillation (ENSO) variations, and atmospheric changes. In order to better understand those factors that control hurricane magnitude and frequency, a long-term record spanning the entire Gulf of Mexico coast is needed. Here we present a detailed record from ca. 5300-900 yr B.P. of past intense hurricane impacts for cores collected from Laguna Madre, Texas, United States. Relative storm intensities were calculated for each event, and the average intense storm impact probability for south Texas was determined to be ~0.46% (annual landfall probability). Previous field studies in Western Lake, Florida, and Lake Shelby, Alabama, reveal similar probability intense hurricane strikes of ~0.39%. Although high-frequency oscillations between warm and dry and cool and wet climate conditions have occurred in Texas through the late Holocene, there has been no notable variation in intense storm impacts across the northwestern Gulf of Mexico coast during this time interval, implying no direct link between these changing climate conditions and annual hurricane impact probability. In addition, there have been no significant differences in the landfall probabilities of storms between the eastern and western Gulf of Mexico during the late Holocene, suggesting that storm steering mechanisms have not varied during this time. doi: 10.1130/G30729.1

Northern peatlands represent one of the largest biospheric carbon (C) reservoirs; however, the role of peatlands in the global carbon cycle remains intensely debated, owing in part to the paucity of detailed regional datasets and the complexity of the role of climate, ecosystem processes, and environmental factors in controlling peatland C dynamics. Here we used detailed C accumulation data from four peatlands anda compilation of peatland initiation ages across Alaska to examine Holocene peatland dynamics and climate sensitivity. We find that 75% of dated peatlands in Alaska initiated before 8,600 years ago and that early Holocene C accumulation rates were four times higher than the rest of the Holocene. Similar rapid peatland expansion occurred in West Siberia during the Holocene thermal maximum (HTM). Our results suggest that high summer temperature and strong seasonality during the HTM in Alaska might have played a major role in causing the highest rates of C accumulation and peatland expansion. The rapid peatland expansion and C accumulation in these vast regions contributed significantly to the peak of atmospheric methane concentrations in the early Holocene. Furthermore, we find that Alaskan peatlands began expanding much earlier than peatlands in other regions, indicating an important contribution of these peatlands to the pre-Holocene increase in atmospheric methane concentrations. doi/ 10.1073/pnas.0911387107 climate seasonality | Holocene therrnal maximum | peatland carbon | Alaska | Siberia

Sedimentologic, stratigraphic, and structural data indicate that the Fountain Formation at Manitou Springs consists of three tectonostrarigraphic units, herein termed the lower, middle, and upper Fountain Formation. Both the lower and middle Fountain Formation were deposited in a fan-delta setting adjacent to the active ancestral Ute Pass fault. The lower is thin and predominantly characterized by deposirional stability as recorded by abundant well-developed, deeply rooted paleosols. The middle Fountain Formation reflects fan progradation and highland rejuvenation as a result of increased activity of the ancestral Ute Pass fault. This activity was likely the result of a basin-ward splay of the ancestral Ute Pass fault with reverse dip-slip motion as indicated by (1) exhumation of the lower Paleozoic Sawatch Formation and (2) fault-parallel folding. The upper Fountain Formation reflects deposition in a NW-SE-trending, braided-river system and appears to postdate movement on the ancestral Ute Pass fault. Lithostratigraphic correlation allows for a Latest Pennsylvanian-Early Permian age for the upper Fountain Formation, thus constraining cessation of the ancestral Ute Pass fault to Middle to Late Pennsylvanian time. The Fountain Formation was deposited within a NW-SE--oriented structural trough (i.e., Woodland Park trough) that separated the ancestral Front Range into a northern block (i.e., ancestral Front Range block) and a southern block (i.e., Ute Pass uplift). The Woodland Park trough was bounded on its southern margin by the ancestral Ute Pass fault, which was active throughout deposition of the lower two Fountain tectonostratigraphic units, during which time sediments were shed northward across the ancestral Ute Pass fault into a marine environment. By the rime of deposition of the upper Fountain Formation, movement on the ancestral Ute Pass fault had ceased or dramatically decreased. During this time, the Fountain Formation records predominantly axially oriented, braided-stream deposition. Comparison of the timing and kinematic history of the ancestral Ute Pass fault with other documented reverse and strike-slip faults of the ancestral Rocky Mountains suggests that: (1) cessation of faulting within the ancestral Rocky Mountains displays a slight east-to-west younging, but the crude age resolution of adjacent basin fill also allows for the possibility of relatively synchronous cessation of faulting, and (2) kinematics of all faults examined are consistent with a NE-SW--oriented maximum horizontal compressional stress field. These inferences contrast with the proposed Laurentian-Gondwanan diachronons closure models for the ancestral Rocky Mountains, which require rotation of the maximum horizontal stress orientation through time and pronounced east-to-west younging of faulting. Rotation of the horizontal stress field may be recorded in multistage, kinematic histories of faults, but multiple faults require study to assess this model. Age constraints on post-tectonic units of the ancestral Rocky Mountains, such as the upper Fountain Formation tectonostratigraphic unit defined herein, are poor and further refinement would greatly aid understanding of the kinematic riming and tectonic driving force of these ancient mountains. doi: 10.1130/B26554.1

The geodynamic context of Iceland provides the rare opportunity to analyse the combined effects of a ridge and a hotspot on deformation processes. From a digital elevation model, field analysis and a compilation of previous work, we propose a synthesis of vertical motions of Iceland during the Holocene with a focus on the post-glacial rebound. We determined two ancient marine limits, one above and one below the present sea level, estimated at 10 ka [+ or -] 300 years and 8150 [+ or -] 350 years BP, respectively. We calculated an uplift phase of 40-170 m with a rate of 2.1-9.2 cm a i between 10 ka [+ or -] 300 years and 8150 [+ or -] 350 years BP, corresponding to the post-glacial rebound of Iceland following the Weichselian glaciation. Spatial variations of the rebound are mainly related to the local glacial dynamics (ice load and deglaciation history) rather than the geodynamic context. However, the relaxation time deduced from uplift data is 4167 years in west Iceland and 2000 years in SSW Iceland. We estimated viscosity from relaxation time, ranging from 2.1 x [10.sup.19] Pas to 3.2 x [10.sup.19] Pas. The significant difference in the relaxation time is due to local variation of the lithospheric thickness as a result of rifting rather than because of a variation of the viscosity. doi: 10.1144/0016-76492009-126.

Terrigenous sediment accumulation within nearshore marine environments is regarded as a major factor inhibiting carbonate production and coral reef accretion. While recent ecological and geological research into reef development under long-term terrigenous sediment influence questions the overly simplistic nature of such views, understanding of the time scales of reef initiation and growth and the morphodynamics of reef accretion in these settings remains limited. Here we present evidence to support recent suggestions that, once established, rapid reef accretion and progradation is possible, but that the restricted accommodation windows in which such reefs develop often result in short-lived (ephemeral) phases of reef building. Specifically, we describe two discrete periods of reef growth within one small (~600 m wide) coastal embayment around a high island on the terrigenous sediment-dominated inner shelf of the central Great Barrier Reef, Australia. These reef-building phases occurred at either end of the Holocene sea-level highstand, the first during the late postglacial marine transgression and early highstand (~6900-4500 calibrated (cal) yr B.P.), the second following the late Holocene regression and stillstand (~1600 cal yr B.P. to present). An ~3000 yr hiatus occurred between these events, probably as a function of subtle changes in sea level and associated shoreline morphodynamics. doi: 10.1130/G30444.1

The end Pleistocene to early Holocene drying of the North American midcontinent is an important case study for understanding regional drought, its drivers, and its impacts. This paper synthesizes pollen, [delta][sup.13]C, eolian, and paleohydrological proxies to document the spatial and temporal patterns in the onset and rate of drying. The timing of onset ranged from 14 to 6 ka with most sites drying between 10 and 8 ka (calendar years ago). The dominant spatial pattern is time transgressive, with interior Great Plains sites beginning to dry before peripheral sites. This time-transgressive trend can be explained as a region-wide drying that caused ecotones to shift eastward, or could indicate a progressive shift in atmospheric drying from west to east. One-third of sites responded rapidly to drying; a cluster of rapid responses occurred ca. 8 ka. The combination of onsets between 14 and 6 ka and rapid responses at 8 ka strongly suggests that (1) the combination of high summer insolation, Laurentide Ice Sheet retreat, and Lake Agassiz drainage drove midcontinental drying, and (2) drying accelerated with Laurentide Ice Sheet collapse at 8.4 ka. Local factors strongly mediate the timing and rate of site responses to regional drying. Local responses to future drying in the Great Plains also should be highly variable, which challenges impact assessments of future climate changes. doi: 10.1130/G30413.1

Paleomagnetic measurements and U-Pb geochronology of alkalic igneous rocks intruding the Ediacaran Cambridge Argillite and the Lower Cambrian Weymouth Formation north of Boston at Nahant, Massachusetts yield a well-constrained paleopole. The oldest intrusive phases are a syenodiorite sill and a granite dike with [sup.206]Pb/[sup.238]U crystallization ages of 490.19 [+ or -] 0.90 Ma and 489.03 [+ or -] 0.82 Ma, respectively. This sequence along with undated mafic sills penetrating both the argillite and Weymouth strata are cut by 488.53 [+ or -] 0.81 Ma gabbro locally associated with 488.48 [+ or -] 0.79 Ma syenite forming a steep-sided intrusive plug. Ten paleomagnetic sampling sites within the mafic sills and the gabbro contain a stable A magnetic component with a mean direction of D = 278.5[degrees], I = -76.7[degrees] ([A.sub.95] = 3.9[degrees], N = 10). This is considered to be the primary magnetization direction because it passes both fold and reversals tests. The corresponding paleopole at 320[degrees]E, 34[degrees]N ([A.sub.95] = 7.2[degrees], N = 10) places the Southeastern New England Avalon Zone at a southerly paleolatitude of 65[degrees] slightly removed from the African margin of Gondwana and suggests that bimodal Nahant magmatism is linked with latest Cambrian--Early Ordovician rifting of West Avalonia to form the Rheic Ocean. Stable B and C magnetic components in Nahant syenodiorite and syenite give rise to virtual geomagnetic poles that track Late Silurian through Carboniferous segments of the North American apparent polar wander path, indicating docking of West Avalonia by mid-Paleozoic time. doi: 10.1130/B26581.1

Paleoclimate reconstructions suggest distinctive changes in the El Nino--Southern Oscillation (ENSO), the dominant mode of tropical climate variability, over the last glacial cycle and throughout the Holocene. However, to the best of our knowledge, no studies provide parallel reconstructions of warm (El Nino) and cold (La Nina) phase variability, thus precluding distinction between variations in ENSO activity and the mean state of the tropical Pacific. Here we provide the first such records, generated using molecular organic geochemical proxies in a sediment core from the Peru margin region. The opposing influences of El Nino and La Nina on coastal upwelling and phytoplankton community structure produce distinct sedimentary sterol records describing the evolution of each ENSO phase. We document changes in surface ocean productivity on the Peru margin over the past 16 ka that indicate enhanced La Nina--like conditions alone during deglaciation, but concomitant increases in both El Nino and La Nina activity during the past 2 ka. We propose that the preponderance of La Nina--like conditions prior to 11.5 ka reflects the influence of waning glacial boundary conditions. By contrast, warm and cold phase covariability during the late Holocene suggests centennial-scale changes in ENSO activity, rather than the Pacific mean state, driven by tropical insolation. doi: 10.1130/G30366.1

Studies of paleo--sea level and past climate have focused upon proxy methods in ice and deep-sea cores and more direct information provided by past shorelines, in some cases preserved as raised or submerged reef deposits in tropical areas. Paleo-shorelines need to be constrained by accurate tectonic history because these environments and their marine deposits can be confused with past tsunami deposits and vice versa. A maximum 21-m-high extensive emerged reef on Oahu, Hawaii, U-series dated to 334 [+ or -]17 ka, together with a mean U-series age of 335 [+ or -] 22 ka (n = 5) for slightly higher, energetic shoreline deposits nearby, suggest a marine isotope stage 9 (MIS 9) highstand, and extend the earlier work indicating a linear uplift for Oahu of 0.060 [+ or -] 0.001 mm/yr over the past 500 k.y. Five of the past six major emerged interglacial highstand reefs on Oahu have been identified, and these data provide little evidence for past maximum sea levels significantly greater than 2 m above the sea level datum at that time. There is currently no evidence for a MIS 11 highstand on Oahu. doi: 10.1130/G30378.1

The contribution of compaction of Holocene strata to sea-level rise, shoreline erosion, and wetland loss is difficult to decipher because of a lack of long-term empirical data. We analyzed more than 360 radiocarbon-dated index points to constrain relative sea levels along the east coast of England during the Holocene and to pruvide estimates of sediment compaction. The isostatic effect of glacial rebound explains regional-scale differences in relative sea levels. Northeast England, the most northern study area, reveals a middle to late Holocene highstand, doi: 10.1130/G30042A.1

Although oolitic sands are widespread throughout the Phanerozoic carbonate rock record, and they are abundant in some modern shallow-marine carbonate systems, recent ooids have not been recognized from any locality in the Pacific Basin. On Aitutaki Atoll (Cook Islands, South Pacific), oolitic sands occur in water depths of 2.1-6.3 m within the lagoon and, less abundantly, on shallower reef aprons. Most ooids are between 150 and 300 [micro]m in diameter, have between 1 and 25 concentric to irregular laminae, and occur with peloids and skeletal grains. Cortical laminae include Mg-caicite crystals with radial, tangential, and random orientations. The occurrence and distribution of oolitic sands on Aitutaki are facilitated by a convergence of hydrodynamic and chemical factors. Wave-driven currents, combined either with flow separation over a sharp increase in depth at the reef apron--lagoon interface or with oceanward flow in the lee of islands, serve to transport ooids without flushing them from the system. Here, pH, alkalinity, and carbonate supersaturation are at some of the highest levels in the tropical Pacific. The restricted occurrence of Holocene oolitic sands in areas of the Pacific and Atlantic Basins with elevated pH and total alkalinity reflects the importance of carbonate saturation thresholds in limiting the spatial distribution of these sands in modern shallow-marine settings. These recent examples are consistent with interpretations of the importance of these variables in determining the distribution, abundance, and cortical mineralogy of oolitic sands throughout the Phanerozoic stratigraphic record of carbonate accumulation. doi: 10.1130/G30332A.1

Displacement rates for normal and reverse faults (n = 57) are generally higher when averaged for the Holocene (~10 ka) than for the late Quaternary (~300 ka) and longer time scales. Holocene acceleration of displacement rates could be attributed to geological processes that produce increases of tectonic tempo. We propose an alternative model in which the observed rate changes arise from variability in earthquake slip and/or recurrence coupled with a sampling bias toward those faults that are best represented at the Earth's surface and that accrued displacement fastest during the Holocene. This model is consistent with displacement rates measured over time intervals of as long as -300 ka for 129 faults from the Taupo Rift, New Zealand. Departures of earthquake parameters and associated displacement rates from their long-term (>300 ka) averages are attributed to fault interactions and occur on time intervals inversely related to these long-term displacement rates and to regional strain rates.

To test whether the Tethyan Himalaya were part of the northern margin of India in the early Palaeozoic we have produced the first primary palaeomagnetic data (bedding-corrected declination 267.5[degrees], inclination 63.0[degrees], [[alpha].sub.95] = 10[degrees]; pole latitude 20.2[degrees]N, longitude 28.6[degrees]E) from low metamorphic grade Ordovician red beds in the Tethyan Himalaya (Shian Formation). The palaeomagnetic data are of excellent quality, and a statistically positive fold test combined with a comparison with late Cambrian--Ordovician Gondwana poles suggests a primary hematite-bearing magnetization, acquired between 470 and 500 Ma. This is in excellent agreement with stratigraphic, faunal and provenance age estimates, and the palaeomagnetic data demonstrate that the Tethyan Himalaya must have been located in proximity to the Indian craton during early Ordovician times, and are therefore consistent with a continuous margin at that time. The Shian Formation pole overlaps with 470-500 Ma Gondwana poles, but ah even better fit can be obtained by invoking a post-Ordovician clockwise rotation of 13[degrees][+ or -] 4[degrees]. Such a rotation is similar in both sense and magnitude to clockwise rotations recorded in primary Triassic sequences as well as Palaeogene palaeomagnetic overprint data from the Tethyan Himalaya: rotations of the Tethyan Himalaya compared with cratonic India are thus probably all of post late Eocene age. Triassic and Early Ordovician data do not imply any crustal shortening between Tethyan Himalaya and cratonic India. However, in the Early Ordovician, India was rotated 90[degrees] compared with its present orientation, and any enlargement of India would not be detected by palaeomagnetic data.

Understanding the timings of interhemispheric climate changes during the Holocene, along with their causes, remains a major problem of climate science. Here, we present a high-resolution [sup.10]Be chronology of glacier fluctuations in New Zealand's Southern Alps over the past 7000 years, including at least tire events during the last millennium. The extents of glacier advances decreased from the middle to the late Holocene, in contrast with the Northern Hemisphere pattern. Several glacier advances occurred in New Zealand during classic northern warm periods. These findings point to the importance of regional driving and/or amplifying mechanisms. We suggest that atmospheric circulation changes in the southwest Pacific were one important factor in forcing high-frequency Holocene glacier fluctuations in New Zealand.

The northern Sierra Nevada and adjacent Basin and Range, western United States, are marked by a widespread regional unconformity at the base of the Eocene-Miocene volcanic and sedimentary section that overlies the Mesozoic batholith and its wall rocks. To help address controversial questions about the origin, uplift, and erosion of the batholith, we compiled a subcrop geologic map of the unconformity prior to Tertiary extension. This simple but underutilized technique reveals the distribution of rock units that could have contributed detritus to the Eocene-Miocene river channels crossing the Sierra Nevada and demonstrates that the Mesozoic Sierra Nevada batholith was continuous to the northeast across the northwestern Basin and Range. More speculatively, the subcrop map implies that Late Cretaceous--Eocene erosional stripping may have been greatest above the axis of the batholith and decreased to the east; thus, drainage in this area may have been eastward and then switched westward in Eocene-Miocene time.

The tectonic and paleogeographic evolution of the Ural-Mongol belt between the cratons of Baltica, Siberia, and Tarim is key to the formation of the Eurasian composite continent during Paleozoic time, but the views on this complicated process remain disparate and sometimes controversial. A study of three volcanic formations of mid-Silurian, Lower to Middle Devonian, and Middle Devonian age from the southwestern boundary of the Chingiz Range (NE Kazakhstan) yields what are interpreted as primary paleomagnetic directions that help clarify the evolution of the belt. A single-polarity characteristic component in mid-Silurian andesites yields a positive intraformational conglomerate test, whereas dual-polarity prefolding components are isolated from the two Devonian collections. Post-folding, reversed-polarity overprint directions have also been isolated and are likely of Permo-Triassic age. These new data can be evaluated together with previously published paleomagnetic results from Paleozoic rocks in the Chingiz Range, and allow us to establish with confidence the polarity of each result, and hence to determine the hemisphere in which the area was located at a given time. We conclude that NE Kazakhstan was steadily moving northward, albeit with variable velocity, crossing the equator in Silurian time. These new paleomagnetic data from the Chingiz Range also agree with and reinforce the hypothesis that the strongly curved volcanic belts of Kazakhstan underwent oroclinal bending between Middle Devonian and Middle Permian time. A comparison of the Chingiz paleolatitudes with those of Siberia shows, insofar as the sparse data allow, similarities between the northward motion of the Chingiz unit and that of Siberia, which imposes important constraints on the evolving paleogeography of the Ural-Mongol belt. Keywords: paleomagnetism, volcanic arc, orocline, Middle Paleozoic, Central Asia, Siberia, paleogeography.