Plant megafossils were collected from the Pondville Conglomerate of the Norfolk basin in southeastern Massachusetts, at Woodworth’s (1894) Canton Junction locality. Before this only conflictingly identified, poorly described, and unfigured plant fossils had been reported from the Norfolk basin. The fossil association suggests a late Pottsvillian age, presumably equivalent to the late Westphalian B of Maritime Canada and Europe. This indicates that the Pondville Conglomerate of the Norfolk basin was deposited during a time interval that is represented by a hiatus in Maritime Canada. Neuropteris obliqua, Neuropteris cf. scheuchzeri, Cordaites principalis, Calamites cisti, Cordaicarpus cf. cordai, a TSamaropsis species, a ?decorticated Sigillaria, and a probable Lonchopteris species have now been identified.

We present a revised model for the formation of southwest Pacific backarc basins from 120 Ma to the present day. Our aim is to improve our understanding of the tectonic regime operating in the region and its consequences for global plate motions. Such an understanding helps explain present-day structures observed on the continental and oceanic lithosphere and the underlying mantle. Regional plate reconstructions were created using gravity and magnetic data from backarc basins, plate-circuit closure, global tomography and existing geological data. Our model predicts convergence between the Australian and Pacific Plates along the Norfolk Ridge from 120 to 100 Ma, followed by the fragmentation of East Gondwana. East-dipping subduction east of Australia was initiated at ca 90 Ma along the Loyalty-Three Kings Ridge and may have trapped Cretaceous quiet-zone crust In the Norfolk Basin. The inception of this subduction system may have provided a driving mechanism for the opening of the Tasman Sea by means of slab pull. A jump in subduction to the east was subsequently initiated along a west-dipping subduction system at ca 45 Ma driven by the collision of the Loyalty Arc with New Caledonia. Consequently, spreading in the North Loyalty Basin occurred by anticlockwise rotation of the subduction hinge between chrons 20 and 16 (43.8–35.3 Ma). This was concurrent to Norfolk Basin opening and formation of the Cook Fracture Zone. Backarc-basin formation then transferred to the South Fiji Basin where magnetic anomalles from chron 12 to 7N (30.9–25.2 Ma) have been identified as two contemporaneous triple junctions. The complex spreading regime witnessed in the South Fiji Basin appears analogous to the North Fiji Basin and may represent the surface expression of a hot, shallow mantle consistent in character to a superswell. The South Fiji Basin ceased forming at ca 25 Ma in response to a major plate reorganisation coinciding with the inception of the Alpine Fault, docking of the Ontong Java Plateau with the Melaneslan Arc and transpressional obduction of the Northland ophiollte. A lull in basin formation throughout most of the Miocene was followed by the reinitiation of backarc basin formation in the Lau Basin (during the past ∼7 million years) and North Fiji Basin (during the past ∼10 million years). All these apparent episodes of backarc-basin formation during the past 45 million years are possibly related to mantle-slab interaction at the 670 km discontinuity.

An erosional hiatus over almost the entire area between Pennsylvania and western New Brunswick suggests that the region was mountainous from the Middle Devonian Acadian orogeny through Pennsylvanian time. Of seven basins or deposits of southeast-era New England, the ages of three (Narragansett, Norfolk, and Worcester) are florally determined as Westphalian B (Middle Pennsylvanian) to Stephanian B or C (Late Pennsylvanian); three lack flora but are of inferred Carboniferous age (North Scituate, Woonsocket, and Pin Hill), and one is of possibly Carboniferous age (Sturbridge). The first three are characterized by flora suggesting a tropical or subtropical climate and by alluvial fan facies deposited in an intermontane basin. Four of these basins or deposits lie in the Avalon Terrane, three just west of the Nashoba Terrane, but none has been recognized in the intermediate Nashoba Terrane. These basin deposits can be correlated with similar deposits in Atlantic Canada. Tectonic effects of the Alleghanian orogeny are many and diverse, resulting in important tectonic controls on the formation and evolution of the coal basins. Grabens surrounded by uplands were formed by extension or strike-slip fault-related extension and were filled with Carboniferous sediments during the earliest Alleghanian orogenic episode. These sediments along with the basement complex, were multiply deformed during Permo-Carboniferous Alleghanian orogenic episodes, which involved folding, thrust faulting, plutonism, regional metamorphism, and strike-slip faulting. Metamorphism throughout the outcrop areas ranges from anchizone to K-spar zone in the Narragansett Basin; anchizone to possibly lower greenschist in the Norfolk Basin; and below the almandine zone in the “Worcester Coal Mine” deposit. Important effects of the tectonism are the widespread anthracitization and tectonic thickening of the low-sulfur and high-ash coals.

Abstract Limited exploratory drilling based on relatively sparse seismic data has occurred since at least 1890 in onshore Late Triassic–Early Jurassic rift basins of the eastern United States (U.S.). Although rich source rocks and thermally generated hydrocarbons have been documented, commercial petroleum accumulations have not been found. Consequently, in 2012 the U.S. Geological Survey (USGS) assessed these basins as having potentially modest volumes of primarily continuous (unconventional) resources. Using these findings and interpretations, what then is the prospectivity of similar age undrilled rift basins in the offshore of the U.S. Central Atlantic? Are there any indications of differences between the offshore and onshore basins in the apparent mode of formation, structural style, amount of inversion, etc. , documented, or suggested by seismic data in these undrilled offshore basins? What do we know, and what can we speculate regarding petroleum system elements and processes in these unexplored basins? Seismic data interpretation suggests most offshore rift basins are generally similar to the Late Triassic–Early Jurassic rift basins onshore. The amount of eroded synrift strata predicted by geohistory modeling in the seismically defined Norfolk basin, offshore Virginia, is similar to that of onshore basins. However, seismic data interpretation also shows differences among some of the offshore basins; e.g. , a rift system northwest of the Yarmouth arch in the northern Georges Bank basin, offshore New England, appears to have less synrift section eroded than most basins in the U.S. Central Atlantic and contains inversion features that appear seismically similar to productive structures found offshore Indonesia.

Abstract Several basins of probable Pennsylvanian rocks are downfolded or downfaulted into the older rocks of New England. The largest of these, and definitely of Pennsylvanian age, is the Narragansett basin of Rhode Island and Massachusetts. Smaller nearby or connected basins are the North Scituate basin, the Woonsocket basin, and the Norfolk basin. Pennsylvanian rocks seem to be present at Worcester, Massachusetts, also, but their extent and relations are not known. The rocks of the Boston basin may be Pennsylvanian or older. The Narrangansett basin is a complex synclinal mass of clastic sedimentary rocks trending northward through eastern Rhode Island, and northeastward into Massachusetts. These rocks lie with marked discordance upon older metamorphic and igneous rocks of Precambrian? and Paleozoic age. The rocks of the basin are chiefly gray and black shale, sandstone, conglomerate, and meta-anthracite. In the northwest part of the basin similar clastic rocks are red. All are of continental origin. The lowermost Pennsylvanian formations are the Pondville and the Bellingham comglomerates. Above the Pondville, or lying directly upon basement, is the Rhode Island formation, which is by far the thickest and the most extensive of the Pennsylvanian formations. The uppermost Pennsylvanian formation is the Dighton conglomerate. The red Wamsutta formation in the northwest is equivalent in part to the Pondville and in part to the lower part of the Rhode Island formation. Basaltic and felsitic rocks are interbedded with the Wamsutta formation. The Purgatory conglomerate may be equivalent to the Dighton or it may be a conglomerate facies of the Rhode Island formation. The total thickness of Pennsylvanian rocks has been estimated to be 12,000 feet. Fossils are mostly of plants, but also include insects and other animals; these suggest an Allegheny to Monongahela age. The sedimentary and structural features characterize the basin as an epieugeosyncline and also relate it to the limnic basins of Europe. The rocks in the northern part of the basin are essentially unmetamorphosed. To the south and southwest they are progressively metamorphosed to garnet staurolite schist and coarse mica schist. The chief mineral resource is meta-anthracite, which has been used only sparingly because of its high ash content and low combustible volatile content.

The Boston basin is one of several late Paleozoic nonmarine sedimentary basins that developed in eastern New England subsequent to the Acadian revolution. Most of the sedimentary rocks in these basins are known to be Pennsylvanian in age; those in the Boston basin are presumably of this age. The principal map units—except for the Blue Hills and Nahant—are the Precambrian basement, the Mattapan and Lynn Volcanic Complexes (Mississippian?), and the Boston Bay Group (Pennsylvanian?). The Boston Bay Group consists of the Cambridge Argillite and the Roxbury Conglomerate. The Roxbury Conglomerate in turn is subdivided, from bottom to top, into the Brookline, Dorchester, and Squantum Members. During the past 25 years, a series of bedrock tunnels, driven for water supply and drainage purposes, have added greatly to our knowledge. The tunnels, 3 to 3.5 m in diameter, are at a depth of 30 to 90 m below the surface. The total length of these tunnels is 39.57 km; the Dorchester Tunnel, under construction, is another 10.19 km long. New observations and interpretations are as follows: (1) The maximum thickness of the Boston Bay Group is 5,700 m. (2) The Boston Bay Group thins to the south. (3) The Roxbury Conglomerate, with a maximum thickness of 1,310 m, is a southerly facies of the lower part of the Cambridge Argillite. (4) The Cambridge Argillite reaches a maximum thickness of 5,700 m in the northern part of the basin. (5) The sedimentary rocks were derived from a highland to the south. The most important new results that bear on structure are that (1) the Northern border fault, where exposed in a tunnel, dips 55°N; (2) the Charles River syncline, exposed in two tunnels 10.5 km apart, plunges 19° in a direction N84°E; and (3) many minor folds and faults complicate the structure. Although no tunnel crosses the Blue Hills, a new interpretation of the structure is presented. The volcanic complex of that area was erupted onto flat-lying Cambrian sedimentary rocks. The Quincy Granite and Blue Hill Granite Porphyry were injected into the horizontal Cambrian strata and volcanic complex. After a period of uplift and erosion, the Pennsylvanian strata of the Norfolk basin were deposited. All the rocks were then folded into a syncline, the vertical north limb of which is now the Blue Hills. The Blue Hills were then thrust northward over the Boston basin.

Abstract The Reinga Basin occupies a northwest-southeast bathymetric d epression between the West Norfolk and Reinga ridges and has an area of about 100,000 sq. km. Rock samples have been dredged from surrounding ridges, but no boreholes have been drilled. We present a seismic stratigraphy developed using 5,135 line km of new 2D seismic-reflection data and 20,000 line km of older data, and we tie this stratigraphy to boreholes in the nearby Northland and Taranaki basins. We identify six phases of basin evolution. The first phase involved extension across northwest-trending normal faults. The region subsided passively during phase 2, and we infer from regional considerations that this phase lasted from Late Cretaceous until middle Eocene time. Phase 3 was late Eocene compression, which we interpret to be related to the initiation of the Tonga-Kermadec subduction. This led to uplift and erosion of the West Norfolk and Reinga ridges and deposition of detrital material at the center of the Reinga basin. Oligocene to early Miocene regional subsidence (phase 4) resulted in flooding of structures created during phase 3. Uplift of the Wanganella Ridge, in the northwest part of the Reinga Basin, occurred at the end of the early Miocene (phase 5). The last phase is tectonically passive, but with ongoing sedimentation up until the present day (phase 6). Upper Cretaceous units in the nearby Taranaki Basin contain coaly source rocks, and coal has been dredged from the ridge on the southwest margin of the Reinga Basin. Maturation models of three sites in the Reinga Basin predict that Cretaceous type III coaly source rocks within basal strata would begin to generate and expel petroleum in early Cenozoic time and expulsion would continue to the present day. The top of the oil expulsion window is modeled at 4.0 +/- 0.5 km below the sea bed, implying a potential kitchen area of approximately 15,000 sq km for Cretaceous source rocks, or a broader area if Jurassic source rocks are present. Most oil and gas expulsion is predicted to be later than the Eocene to Miocene folding and reverse faulting events that created structural traps. It is outside the scope of our study to develop play concepts or analyze direct hydrocarbon indicators, but our regional stratigraphic and tectonic study, combined with a consideration of petroleum system components that may be present, indicates that the Reinga Basin is prospective for oil and gas.

Abstract Convergence and subduction started in the Late Paleocene, to the east of New Caledonia in the South Loyalty Basin/Loyalty Basin, leading to the formation of the Subduction–Obduction Complex of Grande Terre. Convergence during the Eocene consumed the oceanic South Loyalty Basin and the northeasternmost margin of Zealandia (the Norfolk Ridge). The attempted subduction of the Norfolk Ridge eventually led to the end-Eocene obduction. Intra-oceanic subduction started in the South Loyalty Basin, as indicated by high-temperature amphibolite (56 Ma), boninite and adakite series dykes (55–50 Ma) and changes in the sedimentation regime (55 Ma). The South Loyalty Basin and its margin were dragged to a maximum depth of 70 km, forming the high-pressure–low-temperature Pouébo Terrane and the Diahot–Panié Metamorphic Complex, before being exhumed at 38–34 Ma. The obduction complex was formed by the stacking from NE to SW of several allochthonous units over autochthonous Zealandia, including the Montagnes Blanches Nappe (Norfolk Ridge crust), the Poya Terrane (the crust of the South Loyalty Basin) and the Peridotite Nappe (the mantle lithosphere of the Loyalty Basin). A model of continental subduction accepted by most researchers is proposed and discussed. Offshore continuations and comparable units in Papua New Guinea and New Zealand are presented.

Abstract The SW Pacific region consists of a succession of ridges and basins that were created by the fragmentation of Gondwana and the evolution of subduction zones since Mesozoic times. This complex geodynamic evolution shaped the geology of New Caledonia, which lies in the northern part of the Zealandia continent. Alternative tectonic models have been postulated. Most models agree that New Caledonia was situated on an active plate margin of eastern Gondwana during the Mesozoic. Extension affected the region from the Late Cretaceous to the Paleocene and models for this period vary in the location and nature of the plate boundary between the Pacific and Australian plates. Eocene regional tectonic contraction included the obduction of a mantle-derived Peridotite Nappe in New Caledonia. In one class of model, this contractional phase was controlled by an east-dipping subduction zone into which the Norfolk Ridge jammed, whereas and in a second class of model this phase corresponds to the initiation of the west-dipping Tonga–Kermadec subduction zone. Neogene tectonics of the region near New Caledonia was dominated by the eastwards retreat of Tonga–Kermadec subduction, leading to the opening of a back-arc basin east of New Caledonia, and the initiation and southwestwards advance of the New Hebrides–Vanuatu subduction zone towards New Caledonia.

We review the tectonic evolution of the southwest Pacific east of Australia from ca 120 Ma until the present. A key factor that developed early in this interval and played a major role in the subsequent geodynamic history of this region was the calving off from eastern Australia of several elongate microcontinental ribbons, including the Lord Howe Rise and Norfolk — New Caledonia Ridge. These microcontinental ribbons were isolated from Australia and from each other during a protracted extension episode from ca 120 to 52 Ma, with oceanic crust accretion occurring from 85 to 52 Ma and producing the Tasman Sea and the South Loyalty Basin. Generation of these microcontinental ribbons and intervening basins was assisted by emplacement of a major mantle plume at 100 Ma beneath the southern part of the Lord Howe Rise, which in turn contributed to rapid and efficient eastward trench rollback. A major change in Pacific plate motion at ca 55 Ma initiated east-directed subduction along the recently extinct spreading centre in the South Loyalty Basin, generating boninitic lithosphere along probably more than 1000 km of plate boundary in this region, and growth of the Loyalty-D'Entrecasteaux arc. Continued subduction of South Loyalty Basin crust led to the arrival at about 38 Ma of the 70–60 million years old western volcanic passive margin of the Norfolk Ridge at the trench, and west-directed emplacement of the New Caledonia ophiolite. Lowermost allochthons of this ophiolite are Maastrichtian and Paleocene rift tholeiites derived from the underthrusting passive margin. Higher allochthonous sheets include a poorly exposed boninitic lava slice, which itself was over-ridden by the massive ultramafic sheets that cover large parts of New Caledonia and are derived from the colliding forearc of the Loyalty-D'Entrecasteaux arc. Post-collisional extensional tectonism exhumed the under thrust passive margin, parts of which have blueschist and eclogite facies metamorphic assemblages. Following locking of this subduction zone at 38-34 Ma, subduction jumped east-ward, to form a newwest-dipping subduction zone above which formed the Vitiaz arc, that contained elements which today are located in the Tongan, Fijian, Vanuatu and Solomons arcs. Several episodes of arc splitting fragmented the Vitiaz arc and produced first the South Fiji Basin (31-25 Ma) and later (10 Ma to present) the North Fiji Basin. Collision of the Ontong Java Plateau, a large igneous province, with the Solomons section of the Vitiaz arc resulted in a reversal of subduction polarity, and growth of the Vanuatu arc on clockwise-rotating, older Vitiaz arc and South Fiji Basin crust. Continued rollback of the trench fronting the Tongan arc since 6 Ma has split this arc and produced the Lau Basin-Havre Trough. This southwest Pacific style of crustal growth above a rolling-back slab is applied to the 600-220 Ma tectonic development of the Tasman Fold Belt System in southeastern Australia, and explains key aspects of the geological evolution of eastern Australia. In particular, collision between a plume-triggered 600 Ma volcanic passive margin and a 510–515 Ma boninitic forearc of an intra-oceanic arc had the same relative orientation and geological effects as that which produced New Caledonia. A new subduction system formed probably at least several hundred kilometres east of the collision zone and produced the Macquarie Arc, In which the oldest lavas were erupted ca 480 Ma. Continued slab rollback induced regional extension and the growth of narrow linear troughs in the Macquarie Arc, which persisted until terminal deformation of this fold belt in the late-Middle to Late Devonian. A similar pattern of tectonic development generated the New England Fold Belt between the Late Devonian and Late Triassic. Parts of the New England Fold Belt have been broken from Australia and moved oceanward to locations in New Zealand, and on the Lord Howe Rise and Norfolk – New Caledonia Rise, during the post-120 Ma breakup. Given that the Tasman Fold Belt System grew between 600 and 220 Ma by crustal accretion like the southwest Pacific since 120 Ma, facing the open Pacific Ocean, we question whether the eastern (Australia–Antarctica) part of the Neoproterozoic Rodinian supercontinent was Joined to Laurentia.