This study improves porosity conceptualization in the Silurian (Wenlock) dolomitic Lockport Group using core-scale analysis of relationships between depositional facies and the distribution of macroporosity. This dolostone succession forms a crucial regional aquifer, and its shallowly buried to outcropping strata in the study region of Elora (Ontario, Canada) correlate with more deeply buried (>400 m) petroliferous strata in the flanking Michigan and Appalachian basins. Periods of deposition recorded in the local Lockport Group lithofacies succession were influenced by eustasy and paleo-forebulge movement. Initial deposition established variably thick crinoid-tabulate coral shoals in rising accommodation space over a beveled paleosurface. Thickest shoals (similar to 30 m) are succeeded by tabulate coral mud mounds with stromatactis whereas thin shoals (similar to 15 m) are overlain by argillaceous cherty dolomudstone. Difference in water depth was eliminated through accumulation of subtidal dolomudstone between mounds while stromatoporoiddominated buildups formed on mound tops. Continued shallowing resulted in regionally extensive fossiliferous peritidal facies. Inter-basin correlation suggests that shallowing in the Lockport succession was coeval with migration of mud mounds into the Michigan Basin and deepening in the Appalachian Basin. In the Lockport succession, about 40% of porosity is fabric-selective, represented by primary (fenestral, intraparticle) and early secondary (moldic) porosity. Fabric-selective porosity favors those facies dominated by tabulate coral, bivalves, and gastropods. An additional similar to 10% of total porosity is non-fabric-selective (e.g., fractures, vugs, channels) yet exhibits a clear facies influence: solution-enhanced fractures bounding thin crinoid dolorudstone beds and channels developed along some facies boundaries. Remaining porosity is non-fabric-selective and exhibits a more subtle facies influence. This study demonstrates the importance of considering the influence of specific facies on porosity in formation-level hydrogeological analysis.

The Clam Bank Formation records renewed middle Paleozoic, post-Salinic, foreland-basin sedimentation in the northern Canadian Appalachian orogen, but its age has been poorly constrained. The echinoderm lobolith Camarocrinus formed the basis of a long-standing late Silurian (Přídolí) age even though the macrofossil assemblage has received little attention. Previous age assessments, including an early Lochkovian interpretation based on palynomorphs, suffered from contemporary uncertainty of, or subsequent changes to, biostratigraphic zonation. Updated taxonomy and regional stratigraphy, along with addition of new fossil material, demonstrate early Lochkovian macro- and microfossil assemblages, including the species of Camarocrinus. This enables revision of middle Paleozoic paleoenvironmental frameworks within the Canadian Appalachian orogen. In the latest Přídolí, the lowermost Clam Bank Formation was part of a platform-interior coastal plain behind a rimmed shelf (now in the Gaspé Belt) in the northern Quebec Embayment. Early Lochkovian transgression established a mixed siliciclastic–carbonate seaway in the platform interior coeval with shelf-margin drowning. This history coincides with Gedinnian transgression in northern Europe but regression within the nearby Arisaig basin (Nova Scotia), the contrast illustrating local tectonic control on base level. A diverse but poorly preserved Clam Bank macrofaunal assemblage occupied a high-energy, temperate, terrigenous-dominated nearshore setting. Faunal constituents reflect mixing of Eastern Americas and Old World fauna, Silurian holdovers, and appearance of taxa earlier than elsewhere in North America. Megaplant fossils, palynomorphs, and arthropod trackways identify a wet and dry coastal terrestrial habitat. Middle Lochkovian regression appears to have terminated the marine basin.

Biformites insolitus Linck, 1949 and very shallow, partially facetted, vertical burrows occur together in calcareous siltstone as convex hypichnia of sandstone on bedding soles within the Lower Devonian Clam Bank Formation, western Newfoundland. The ichnofossils occur within thinly interstratified siltstone and sandstone that accumulated within a physically stressed, euryhaline, peritidal paleoenvironment. B insolitus consists of straight to sinuous, narrow (2-3 mm), strap-like imprints commonly up to 7 cm long that display a medial axial depression and paired (opposite) conical (rounded blunt tipped) to irregular blocky and rectangular-shaped protuberances. These structures are interpreted to represent the impressions of ophiuroid arms, including representations of tube feet and ambulacral skeletal structure. Ornamentation detail appears proportional to the depth of an imprint and is a measure of the amount of downward force of an arm relative to horizontal motion. Apparent branching of imprints represents arm overprints. Incompletely facetted transverse sections of burrows, also filled with sandstone, warrant comparison with the ichnogenus Pentichnus, but incomplete preservation of a possible higher-order symmetry defers ichnotaxonomic designation. The imprints are very shallow (<1 cm) and fit with very near-surface burrowing as observed among some modern ophiuroids. The burrows are either a variant of Pentichnus, thereby expanding its current stratigraphic range, or broaden a unique ichnotaxobase of facetted burrows. A middle Paleozoic record of B. insolitus narrows the current disparity with the post-Cambrian ophiuroid skeletal record. Its spatial association with burrows in a peritidal paleoenvironment reinforces the complex behavior of ophiuroids, their ecological breadth, and opportunistic behavior.

The upper Silurian(?) to Lower Devonian (Lochkovian) Clam Bank Formation is the most northerly exposed middle Paleozoic foreland-basin succession in the Appalachian orogen. Understanding of its sedimentary history is poor, and there are contradictory interpretations of placement of its lower structural boundary. Our study redefines the lithostratigraphy and subdivides the ∼600 m thick formation into three paleoenvironmental successions: a lower coastal plain setting with fluvial channels giving way upsection to coastal flats with carbonate, colluvium with reworked paleosol material, and aeolian (silt) deposits; a middle coastal zone succession following marine transgression and deposition of shoreface sandstone; and an upper alluvial succession host to pedogenic and groundwater calcretes. A basal disconformity, though not exposed, is inferred from lithic and geochemical evidence for sediment mixing with underlying Upper Ordovician sources in the lowermost part of the formation. This supports previous interpretations of Silurian uplift along the Laurentian margin in response to the Salinian orogeny. Sedimentary provenance indicates quartzo-feldspathic sources throughout the formation, and sediment-transport indicators identify a northeast–southwest-oriented basin with northwest-directed fluvial input. U–Pb detrital zircon distributions associated with the paleocolluvium and younger transgressive sandstone document upsection loss of prominent age peaks of late Grenville (∼0.98 Ga) and pre-Grenville (1.5, 1.65, and 1.75 Ga) sources. The coastal plain succession and related detrital-zircon signature imply a mixture of distal and proximal sediment sources, the latter related to erosion of a weathered upland and exhumed Precambrian inliers in western Newfoundland. A more regional provenance signature with marine transgression suggests sediment transport in response to Acadian orogenesis.

Petrology, geochemistry, fluid inclusions and U-Pb dating of a wide (30 cm) calcite vein in Upper Ordovician (Sandbian) limestone characterize a hydrochemical microcosm of changing fluid sources and carbon pathways related to burial, then uplift during the Phanerozoic along the Ottawa-Bonnechere graben, central Canada. U-Pb dating of the host limestone produces an age younger than its chronostratigraphic age suggesting the impact of diagenesis, otherwise well-defined petographically. An interred calcite fragment dated as Cambrian may highlight a platform source in this part of the graben hitherto unrecognized stratigraphically. The vein was initiated with extension across a high-angle narrow (2 cm) fault gouge allowing incursion of hot (80-125 degrees C) basinderived (Mg, Ca)-Cl-2 brine recorded by a saddle dolomite-dedolomite-calcite succession, not isotopically datable. Microbial methanogenesis occurred in initial narrow structural recesses giving way to recycled sedimentary bicarbonate with fracture widening. The oldest datable vein calcite (122 +/- 5 Ma) consists of microcrystalline geopetal cumulates of vadose meteoric origin demarcating renewed carbonate formation following a period of near-surface alteration, dissolution, and microfracturing of the prior vein calcite during uplift. Initial Pb-207/Pb-206 ratios are consistent with average crust (0.819 +/- 0.003), and delta O-18 signatures identify a meteoric signature similar to the host rock. Subsequent interlayering of isopachous calcite and pyrite, with an age of 105 +/- 3 Ma for the calcite, defines onset of a meteoric phreatic environment. The role of microbial sulphate reduction is characterized isotopically. Initial Pb-207/Pb-206 ratios scatter below the crustal average (0.84-0.76) that, along with a meteoric delta O-18 signature, suggest incursion of a new fluid reservoir. A subsequent Sr, Mn, Ba-bearing-magnesium calcite marks the beginning of sustained phreatic meteoric dilution for the remaining vein history. Stable (C, O) isotopes document varying temperature and bicarbonate mixtures of sedimentary and bacterial (sulphate reduction) origins associated with a meteoric fluid. This calcite has a mean age of 94 +/- 2 Ma and displays the widest range of initial Pb-207/Pb-206 ratios, which scatter down to 0.65. Stable and radiogenic isotopic compositions suggest a meteoric setting largely influenced by a crustal fluid reservoir of long residence time and-or transport resulting in leaching of radiogenic minerals. The final vein calcite, also of meteoric origin, has an Sr-87/Sr-86 ratio similar to that of the initial basin brine, yet with C-13 signatures that characterize a source of oxidized methane. U-Th series analysis delimits an age older than 0.5 Ma. This stage of vein calcite likely arises through meteoric fracking of Ordovician source rocks during continued basin inversion. In summary, initial brine influx followed by a shallow-crustal meteoric realm document structurally focused fluid migration with and following early Mesozoic graben exhumation. The phreatic meteoric regime of Early Cretaceous age spans a similar to 20 Ma period coincident with transient magmatism arising from near passage of the Great Meteor Hotspot. Regional paleohydmlogy appears to have been influenced for similar to 10 Ma after plume passage.

The Middle to Upper Ordovician foreland succession of the Ottawa Embayment in central Canada is divided into nine transgressive‐regressive sequences that defines net deepening of a platform succession over ~15 m.y. from peritidal to outer ramp settings, then a return to peritidal conditions over ~3 m.y. related to basin filling by orogen‐derived siliciclastics. With a backdrop of net eustatic rise through the Middle to Late Ordovician, there are several different expressions of structural influence on sequence development in the embayment. During the Middle Ordovician (Darriwilian), foreland‐basin initiation was marked by regional onlap with abundant synsedimentary deformation across a faulted trailing‐margin platform interior; subsequent craton‐interior uplift resulted in voluminous influx of siliciclastics contemporary with local structurally influenced local channelization; then, a formation of a platform‐interior shale basin defines continued intrabasin tectonism. During the Late Ordovician (Sandbian, early Katian), structural influence was superimposed on sea‐level rise as indicated by renewed local development of a platform‐interior shale basin; differential subsidence and thickness variation of platform carbonate successions; abrupt deepening across shallow‐water shoal facies; and, micrograben development coincident with foreland‐platform drowning. These stratigraphic patterns are far‐field expressions of distal orogen development amplified in the platform interior through basement reactivation along an inherited buried Precambrian fault system. Comparison of Upper Ordovician (Sandbian‐lower Katian) sequence stratigraphy in the Ottawa Embayment with eustatic frameworks defined for the Appalachian Basin reveals greater regional variation associated with Sandbian sequences compared to regional commonality in base level through the early Katian.

Small Ordovician sedimentary outliers, including Brent Crater, within the northern Ottawa–Bonnechere graben are remnants of a once expansive Upper Ordovician sedimentary cover extending across the southern Canadian Shield. Facies successions along with updated macrofossil and conodont biostratigraphy, and isotope (C, O, Sr) chemostratigraphy provide additional insights into the terrestrial-to-marine transformation, carbonate-platform development, and oceanographic communication across the southern Laurentian platform. Four of the outliers document Sandbian shoreline-to-nearshore deposition: near Deux Rivières, Manitou Islands, the upper part of the Brent Crater sedimentary fill, and at nearby Cedar Lake. Marine transgression initially reworked local fine-grained to boulder-rich regolith within high-energy shoreface siliciclastic environments that gave way to low- to high-energy inner carbonate-ramp setting. Continued transgression resulted in more offshore rhythmic and diverse lithofacies successions defining mixed heterozoan, photozoan, and microbial productivity and marine isotope (C, Sr) signatures, but δ13C excursions suggest periods of greater mixing of terrestrial and marine carbon reservoirs. Lower Katian strata are preserved near Lake Nipissing and characterize deepening from high-energy ooid-heterozoan skeletal shoals to deeper water mid-ramp siliciclastics and skeletal carbonates, host to a Cruziana ichnofacies. An upsection decline in δ13C values through this succession may identify deposition during the post-peak decline of the global Guttenberg δ13C excursion. This lithic succession fits well with contemporary expansion of heterozoan skeletal lithofacies across the Laurentian platform, yet the presence of ooids identifies prevailing warm waters within the platform interior during early stages of transgression.

Positive δ13Ccarb excursions are correlated through an upper Turinian to lower Chatfieldian carbonate-platform succession along the axis of the Ottawa Embayment and into outliers of the northern Ottawa-Bonnechere graben in central Canada. Successive Turinian excursions (E1 and E2) are lithostratigraphically constrained by erosional surfaces and hosted within the Watertown and overlying L'Orignal formations, respectively, the latter coeval with the Selby Formation in the adjacent northern Appalachian Basin. The excursions coincide with periods of regional transgression, but geographic patterns of 13C depletion versus enrichment coincide with structurally defined areas of stratigraphically condensed and preferentially thickened formation successions, respectively. Differential subsidence is interpreted to have created bathymetric variation resulting in intrabasinal restriction of seawater exchange between these areas, with preferential Corg recycling with stratigraphic condensation. By early Chatfieldian time, segmentation of the once regional carbonate platform (L'Orignal Formation) produced a regional mosaic of low-energy muddy carbonate banks (Rockland Formation) and a deeper water platform (lower Hull Formation) settings subject to fluctuating high to low energy current flow. Excursion E3 occurs in both successions, but 13C enrichment is associated only with the bank-top muddy facies. This may identify preferential photosynthetic drawdown of 12C across the bank tops due to limited seawater exchange across the bank-deeper platform boundaries. Excursions E1 to E3, and a younger excursion (E4) in the Hull Formation, are correlated with varying confidence with excursions across southern Laurentia, excursion E3 being the local expression of the Guttenberg δ13C excursion. Our study supports local modulation of regional, if not global, δ13C excursions arising from structurally controlled changes in oceanography and productivity.

Late Ordovician (Turinian–Chatfieldian) drowning of a mixed carbonate–siliciclastic platform within the Taconic Orogen (Newfoundland Appalachians) is recorded by net deepening of an initial warm, shallow-water platform succession (Lourdes Formation) culminating in a metre-scale thick condensed interval that characterizes a drowning succession punctuated by storm deposits. Composition of transported material suggests that seaward drowning was coupled with back-stepping of a high-energy carbonate factory related to hinterland uplift and erosion that would eventually lead to drowning of the outer platform beneath marine-transported siliciclastic sediments (Winterhouse Formation). In the new offshore shelf setting, a sparse reciprocal stratigraphy of fine- to very coarse-grained phosphatic carbonate and mixed sediment is interpreted to document gravity-flow deposition downgradient from either a sustained or episodically developed high-energy cool-water carbonate source along the inner shelf. Transported carbonate was cemented rapidly at temperatures no warmer than 16 °C–23 °C, possibly within a seasonal oceanic thermocline. An upsection decrease in abundance of carbonate by the early Edenian is associated with a dramatic increase in siliciclastic supply. The Turinian–Edenian succession of platform drowning, oceanographic transition to cool-water carbonate production, and, later, its termination by increased siliciclastic supply reflects a first-order tectonic control proximal to uplift within the Taconic Orogen. Similar structural and oceanographic changes along the contemporary distal Laurentian margin provides the basis, with improved biostratigraphic control, for future analysis of the significance of proximal–distal stratigraphies in response to regional foreland tectonism.

Resumen es: La acumulacion de metales traza en agua, sedimentos y organismos es de la mayor preocupacion debido a los numerosos efectos adversos que los metales pes...

Three stages of carbonate-platform development are preserved in the upper Turinian – lower Chatfieldian succession of the Ottawa Group in the Ottawa Embayment and represent deposition along the Late Ordovician Taconic foreland interior of paleo-southern Laurentia. Compared with contemporary stratigraphy in the adjacent northern Appalachian (southern Ontario, New York state) and western Quebec basins, the intermediate Stage 2 succession, which brackets the Turinian–Chatfieldian boundary, preserves embayment-specific stratigraphic patterns. These include: (i) dramatic west-to-east thickening of the upper Turinian Watertown Formation that defines differential subsidence along the present axis of the embayment, (ii) post-Watertown base-level fall defined by appearance of shoreface siliciclastics, (iii) early Chatfieldian marine transgression represented by the proposed L’Orignal Formation that is coeval with but lithologically distinct from the Selby Formation in the northern Appalachian Basin, and (iv) platform segmentation that resulted in a depositional mosaic of shallow banks (Rockland Formation) and equivalent deeper water mico-seaways (lower Hull Formation). The latter event immediately follows accumulation of the Millbrig bentonite, here dated at 453.36 ± 0.38 Ma. Bracketing these local stratigraphic patterns are the bounding stages (1 and 3) represented by the upper Turinian Lowville Formation and middle Chatfieldian Hull Formation, respectively, that contain facies attributes in common with the adjacent basins and characterize inter-regional depositional systems of first warm, then cooler oceanographic conditions. Stage 2 identifies a structurally controlled transition between these end-member stages: a far-field response in the foreland interior, localized along the axis of a late Precambrian fault system, to contemporary change in subsidence rates and tectonomagmatic events along the Laurentian margin.

Questions surrounding the chronology, place, and character of the initial human colonization of the Americas are a long-standing focus of debate. Interdisciplinary debate continues over the timing of entry, the rapidity and direction of dispersion, the variety of human responses to diverse habitats, the criteria for evaluating the validity of early sites, and the differences and similarities between colonization in North and South America. Despite recent advances in our understanding of these issues, archaeology still faces challenges in defining interdisciplinary research problems, assessing the reliability of the data, and applying new interpretative models. As the debates and challenges continue, new studies take place and previous research reexamined. Here we discuss recent exploratory excavation at and interdisciplinary data from the Monte Verde area in Chile to further our understanding of the first peopling of the Americas. New evidence of stone artifacts, faunal remains, and burned areas suggests discrete horizons of ephemeral human activity in a sandur plain setting radiocarbon and luminescence dated between at least ~18,500 and 14,500 cal BP. Based on multiple lines of evidence, including sedimentary proxies and artifact analysis, we present the probable anthropogenic origins and wider implications of this evidence. In a non-glacial cold climate environment of the south-central Andes, which is challenging for human occupation and for the preservation of hunter-gatherer sites, these horizons provide insight into an earlier context of late Pleistocene human behavior in northern Patagonia.

Jurassic strata along the southern margin of Junggar Basin are important petroleum system elements for exploration in northwest China. The Lower and Middle Jurassic source rock effectiveness has been questioned as exploration progresses deeper into the basin. These source rocks are very thick and are distributed widely. They contain a high total organic carbon composed predominantly of Type III kerogen, with some Type II kerogen. Our evaluation of source rock petroleum generation characteristics and expulsion history, including one-dimensional basin modeling, indicates that Jurassic source rocks are gas prone at deeper depths. They reached peak oil generation during the Early Cretaceous and began to generate gas in the Late Cretaceous. Gas generation peaked in the Paleogene-Neogene. Source rock shales and coals reached petroleum expulsion thresholds at thermal maturities of 0.8% and 0.75% vitrinite reflectance, respectively, when the petroleum expulsion efficiency was similar to 40%. The petroleum generated and expelled from these source rocks are 3788.75 x 10(8) and 1507.55 x 10(8) t, respectively, with a residual 2281.20 x 10(8) t retained in the source rocks. In these tight reservoirs, a favorable stratigraphic relationship (where tight sandstone reservoirs directly overlie the source rocks) indicates short vertical and horizontal migration distances. This indicates the potential for a large, continuous, tight-sand gas resource in the Lower and Middle Jurassic strata. The in-place natural gas resources in the Jurassic reservoirs are up to 5.68 x 10(12) - 15.14 x 10(12) m(3). Jurassic Badaowan and Xishanyao coals have geological characteristics that are favorable for coal-bed methane resources, which have an in-place resource potential between 3.60 x 10(12) and 11.67 x 10(12) m(3). These Lower and Middle Jurassic strata have good shale gas potential compared with active US shale gas, and the inferred in-place shale gas resources in Junggar Basin are between 20.73 x 10(12) and 113.89 x 10(12) m(3). This rich inferred conventional and unconventional petroleum resource in tight-sand, coal-bed, and shale gas reservoirs makes the deeper Jurassic strata along the southern margin of Junggar Basin a prospective target for future exploration.

A condensed (similar to 20-m-thick) marine transgressive-highstand succession comprises the upper San Julian Formation (upper Oligocene-lower Miocene) of the northern retroarc Austral Basin, southern Patagonia. Mixed-sediment fades identify a shelf-interior setting, part of an overall warm-temperate regional platform of moderate energy. Giant oyster-dominated skeletal-hiatal accumulations along the maximum flooding surface and forming high-energy event beds in the highstand succession preserve relict micrite in protected shelter porosity, and identify periods of reduced sediment accumulation. The stratigraphic distribution of marine-derived glaucony and diagenetic carbonates is spatially related to sequence development. Depositional siderite coincides with prominent marine transgression, defining transient mixing of marine and meteoric waters across coastal-plain deposits. Chemically evolved autochthonous glaucony coincides with periods of extended seafloor exposure and transgressions that bracket the marine succession, and within the oyster-dominated skeletal accumulations. Seafloor cement, likely once magnesian calcite, formed in association with an encrusting/boring biota along the maximum flooding surface in concert with incursion of cool (11-13 degrees C) water. The cement is present locally in skeletal event beds in the highstand succession suggesting a possible association with high-order base-level change and cooler water. As the highstand succession coincides with elevated global sea level in the late Oligocene-early Miocene, the locally marine-cemented glauconitic skeletal event beds in the highstand succession may identify higher order glacio-eustatic control. Local stratal condensation, however, is best explained by regional differences in basement subsidence. In the burial realm, carbonate diagenesis produced layers of phreatic calcrete coincident with skeletal-rich deposits. Zeolite (clinoptilolite-K) cement is restricted to the lowermost marine transgressive interval probably due to initial elevated metastability of reworked weathered silicates. Clay (illite)-cement is restricted to siliciclastic-rich intervals wherein skeletal carbonate did not buffer pore-water pH. Diagenetic carbonate geochemistry (Sr, Na, and delta O-18 and delta C-13) shows that, with burial, the transgressive and highstand system tracts developed as distinct paleoaquifers resulting from different proximities to meteoric recharge zones. (C) 2014 Elsevier B.V. All rights reserved.

The Neoproterozoic Wynniatt Formation, part of the upper Shaler Supergroup, is exposed in the Minto Inlier of Victoria Island, Canada, and was deposited in the intracratonic Amundsen Basin. The unit consists of a southwest-thickening (480 to 1000 m over ~ 300 km) shallowing-upward succession of three carbonate ramp sequences separated by regional unconformities. In ascending order: 1) inner to outer ramp carbonate facies, gradationally overlain by siliciclastic rocks of a pro-delta slope setting; 2) inner to mid-ramp subtidal carbonate facies, including a regional stromatolitic barrier system; and 3) outer ramp carbonate (gravity flow) facies overlain by shallowing-upward subtidal to intertidal, mixed siliciclastic-carbonate inner ramp facies. Spatial arrangements of nineteen lithofacies illustrates that each carbonate ramp sequence represents part of a distally steepened, storm-dominated carbonate ramp, with an interval of deep-water carbonate rocks coincident with oceanic restriction that elevated salinity. Migration of depocentre loci for successive ramp stages reflects changing patterns of subsidence. This may identify far-field extensional effects in this intracratonic basin because ages of the lower (~ 850 Ma) and middle (~ 761 Ma) formation bracket initiation of supercontinent (Rodinia) break-up. Our work offers an improved sedimentary framework for interbasinal correlation with coeval Neoproterozoic basins. It highlights temporal changes in carbonate facies compared to older carbonate successions in the Shaler Supergroup, and it defines depositional context for the Tawuia-Chuaria assemblage zone, providing important interbasinal biostratigraphic correlation.

Narrow (tens of meters) vertical bodies of dolomite replace a nonporous Upper Ordovician (lower Chatfieldian) limestone along the leading limb of an asymmetric faulted anticline well inboard (similar to 300 km) of the northern Appalachian orogen, central-east Canada. Patterns of geometry, texture, and geochemistry suggest that dolomitizing fluids were focused (possibly along microfractures) within a paleosinistral transpressive stress field generated with reactivation of an underlying Neoproterozoic fault system. Strike-slip failure of the developing anticline resulted in fracture-and fault-controlled fluid flow from which precipitated saddle dolomite. A paragenetic succession of Fe-poor planar-e to ferroan planar-s dolostone marks the peak phase of replacement dolomitization. A subsequent increase (20%-30%) in porosity created through local dissolution of relict limestone was partially occluded by ferroan planar dolomite that, geochemically, is similar to later fracture-fill saddle dolomite. Replacement dolomitization is associated with a slight rise in Sr-isotope ratios (to 0.71085) from Late Ordovician-early Silurian marine signatures. Isotope (C, O, Sr) signatures support influx and mixing of burial fluids that had interacted with local Mg-rich (gabbro, anorthosite, syenite) crystalline basement with a background fluid similar to Late Ordovician seawater or dissolved marine limestone. Dolomitization predated maximum burial in the Late Paleozoic. Fluid inclusion and isotope paleothermometry suggest that dolomitizing temperatures (100 degrees-120 degrees C) were 20 degrees-30 degrees C warmer than associated with prior limestone diagenesis. The dolomitized limestone is an archival record of structure, hydrology, and heat flux that best fits with Taconic tectonism in the latest Ordovician through earliest Silurian.

The Middle to lower Upper Ordovician (Chazyan) platform succession of eastern North America extends landward of the ancient Quebec Embayment along the Laurentian margin, part of a foreland basin peripheral to an arc-collisional plate boundary. The platform grades from seaward reefal carbonate (Chazy Group, Champlain Valley) into platform- and foreland-interior tide- and wave-dominated siliciclastics (Rockdiffe Formation) and restricted peritidal muddy carbonate (Hog's Back Formation). The latter two formations occur in the sedimentary Ottawa Embayment, which overlies the trace of a Neoproterozoic rift. Prominent tectonostratigraphic surfaces bound and subdivide the Chazyan platform-interior succession, and are characterized by abrupt marine transgressions, local synsedimentary faults, and seismogenic beds. The depositional history includes: (1) accumulation of shallow-marine siliciclastics (Rockcliffe Fm) across a differentially faulted paleoplatform; (2) abrupt regional retrogradation (similar to 100 km) of this siliciclastic system, replaced by an intraplatform shale basin (lower Hog's Back Formation); (3) basin fill and development of a low-energy muddy carbonate platform interior (upper Hog's Back Formation) coincident with regional fall in sea level and change in subsidence along the Laurentian margin; and (4) abrupt high-frequency base-level changes preceding regional onlap of Mohawkian (Turinian) shale contemporary with local synsedimentary deformation and rapid subsidence along the distal arc-collisional plate boundary. Structurally controlled sedimentation patterns in the platform (and foreland) interior document episodic tectonism coincident with relatively sustained deposition along the outer platform (the Chazy Group). This difference is interpreted to be a response to foreland-interior flexuring, modified by local reactivation of the Precambrian rift, that was coincident with preferential subsidence at seaward sites more proximal to structural loading along the arc-collision plate boundary.

The Upper Ordovician (Edenian) Lindsay Formation of the Ottawa Embayment represents the final stage of carbonate platform development in the Taconic foreland periphery inboard of the northern Appalachian orogen. The succession overlies a narrow (~60 km) axis of a Neoproterozoic Laurentian rift extending across the Grenville orogen. The Lindsay Formation consists of a lower heavily bioturbated skeletal limestone that represents a warm-water shoal facies following an underlying outer ramp stratigraphy, and an upper division of renewed deep-water deposition with organic-rich shale and fossiliferous lime mudstone. Pyritic deep-water black shale of the westerly advancing Taconic foreland basin disconformably overlies this platform succession. Stratigraphic correlation through the central embayment identifies likely synsedimentary faults and seaward-directed erosion bounding the Lindsay Formation in a region of older Ordovician faults and a change in the lithotectonic character of the crystalline basement. The Late Ordovician shallowing and localization of structural/erosional features are interpreted to record a structural hinge: a local accommodation to, first, foreland periphery uplift, then rapid subsidence related to westerly diachronous foreland subsidence through the platform interior. Spatial association of structures of differing ages suggests that reactivation of inherited weakened crust influenced Late Ordovician sedimentary patterns.

The Great American Carbonate Bank (GACB) comprises the carbonates (and related siliciclastics) of the Sauk megasequence, which were deposited on and around the Laurentian continent during Cambrian through earliest Middle Ordovician, forming one of the largest carbonate-dominated platforms of the Phanerozoic. The Sauk megasequence, which ranges upwards of several thousand meters thick along the Bank's margin, consists of distinctive Lithofacies and fauna that are widely recognized throughout Laurentia. A refined biostratigraphic zonation forms the chronostratigraphic framework for correlating disparate outcrops and subsurface data, providing the basis for interpreting depositional patterns and the evolution of the Bank. GACB hydrocarbon fields have produced 4 BBO and 21 TCFG, mostly from reservoirs near the Sauk-Tippecanoe unconformity. The GACB is also a source of economic minerals and construction material and, locally, serves as either an aquifer or repository for injection of waste material. This Memoir comprises works on biostratigraphy, ichnology, stratigraphy, depositional facies, diagenesis, and petroleum and mineral resources of the GACB. It is dedicated to James Lee Wilson who first conceived of this publication and who worked on many aspects of the GACB during his long and illustrious career.