Deerfield Basin Research Articles

Morphology, Internal Architecture, Facies Model, and Emplacement Mechanisms of Lava Flows from the Central Atlantic Magmatic Province (CAMP) of the Hartford and Deerfield Basins (USA)

The morphology, internal architecture, and emplacement mechanisms of the Central Atlantic Magmatic Province (CAMP) lava flows of the Hartford and Deerfield basins (USA) are presented. The Talcott, Holyoke, and Hampden formations within the Hartford basin constitute distinct basaltic units, each exhibiting chemical, mineralogical, and structural differences corresponding to flow fields. Each flow field was the result of several sustained eruptions that produced both inflated pahoehoe flows and subaquatic extrusions: 1–5 eruptions in the Talcott formation and 1–2 in Holyoke and Hampden basalts, where simple flows are dominant. The Deerfield basin displays the Deerfield basalt unit, characterized by pillow lavas and sheet lobes, aligning chemically and mineralogically with the Holyoke basalt unit. Overall, the studied flow fields are composed of thick, simple pahoehoe flows that display the entire range of pahoehoe morphology, including inflated lobes. The three-partite structure of sheet lobes, vertical distribution of vesicles, and segregation structures are typical. The characteristics of the volcanic pile suggest slow emplacement during sustained eruptive episodes and are compatible with a continental basaltic succession facies model. The studied CAMP basalts of the eastern United States are correlated with the well-exposed examples on both sides of the Atlantic Ocean (Canada, Portugal, and Morocco).

Evidence for Bipedal Prosauropods as the Likely Eubrontes Track-Makers

The tridactyl ichnotaxon Eubrontes giganteus commonly has been attributed to a carnivorous theropod dinosaur similar to Dilophosaurus or Liliensternus. For this to be correct, however, at least five unusual circumstances all must be true. (1) If the Eubrontes track-maker was a theropod, it created the most abundant large tracks found in the Connecticut Valley Hartford and Deerfield basins and yet, for unknown reasons, left no skeletal remains there at all. This pattern also holds true for the Kayenta Formation and Navajo Sandstone in the American Southwest. (2) The cursorial, bipedal, functionally tridactyl prosauropod Anchisaurus, which left two-thirds of the skeletal remains found in these same basins, for unknown reasons left no tracks there at all. (3) If the Eubrontes track-maker was a theropod, by happenstance, it was a theropod exactly the same size as Anchisaurus. (4) If the Eubrontes track-maker was a theropod, then published evidence for herding by Eubrontes track-makers must be due to local paleogeographic factors, not recognizable in the rock record, which created an illusion of herding. (5) The known stratigraphic range of Eubrontes tracks (Norian-Toarcian) by happenstance falls entirely within the known stratigraphic range of bipedal prosauropods (upper Carnian-Toarcian). None of these unusual circumstances need be true, however, if Anchisaurus was the Eubrontes track-maker. Recent reports of an anteriorly directed hallux in the Eubrontes track-maker provide compelling evidence that prosauropods, not theropods, made Eubrontes tracks. Parsimony strongly favors this conclusion and weighs heavily against the idea that the Eubrontes track-maker was a mysterious, elusive theropod whose skeletal remains have evaded discovery for nearly two centuries.

Aquatic insect trackways from Jurassic playa lakes: Reinterpretation ofLunulipes obscurus(Hitchcock, 1865) based on neoichnological experiments

The ichnospecies Lunulipes obscurus is reevaluated and a new diagnosis provided. All samples from Early Jurassic lacustrine deposits of the Deerfield Basin in Massachusetts, USA that were previously determined to bear Lunulipes or Lunulipes-like traces were examined. This reevaluation revealed that the ichnospecies is restricted only to two slabs. The morphology of Lunulipes obscurus suggests that its arthropod maker beat a single pair of legs synchronously. This type of locomotion is used by aquatic insects such as backswimmers (Notonectidae), water boatmen (Corixidae), and predaceous diving beetles (Dytiscidae). Neoichnological experiments with these three taxa indicate that water boatmen produce trackways that are the most similar to the fossil, and hence we conclude that a water boatman or an unknown insect that employed a similar method of swimming produced the Early Jurassic traces. These trackways provide the first tentative evidence of water boatmen in the Deerfield Basin, and, if correctly identified, represent the first trace fossils of this aquatic insect group anywhere.

Lunulipes, a replacement name for the trace fossil Lunula Hitchcock, 1865, preoccupied

Edward Hitchcock (1865) erected the ichnogenus Lunula with a single ichnospecies, L . obscura , for trackways (Fig. 1) that were discovered in the Lower Jurassic Turners Falls Formation of the Deerfield Basin in Massachusetts. As noted by Hantzschel (1965), however, and reiterated by Anderson (1981) later, Hitchcock’s application of that genus name to a trace fossil established an invalid …

Perennial Lakes as an Environmental Control on Theropod Movement in the Jurassic of the Hartford Basin

Eubrontes giganteus is a common ichnospecies of large dinosaur track in the Early Jurassic rocks of the Hartford and Deerfield basins in Connecticut and Massachusetts, USA. It has been proposed that the trackmaker was gregarious based on parallel trackways at a site in Massachusetts known as Dinosaur Footprint Reservation (DFR). The gregariousness hypothesis is not without its problems, however, since parallelism can be caused by barriers that direct animal travel. We tested the gregariousness hypothesis by examining the orientations of trackways at five sites representing permanent and ephemeral lacustrine environments. Parallelism is only prominent in permanent lacustrine rocks at DFR, where trackways show a bimodal orientation distribution that approximates the paleoshoreline. By contrast, parallel trackways are uncommon in ephemeral lacustrine facies, even at sites with large numbers of trackways, and those that do occur exhibit differences in morphology, suggesting that they were made at different times. Overall, the evidence presented herein suggests that parallelism seen in Hartford Basin Eubrontes giganteus is better explained as a response to the lake acting as a physical barrier rather than to gregariousness. Consequently, these parallel trackways should not be used as evidence to support the hypothesis that the trackmaker was a basal sauropodomorph unless other evidence can substantiate the gregariousness hypothesis.

The earliest discoveries of articulated fossil fishes (Actinopterygii) in the United States: A historical perspective

The first articulated fossil fishes (Actinopterygii) unequivocally discovered in the United States were collected in the Early Jurassic lacustrine deposits of the Newark Supergroup. They were reported in 1816 by Benjamin Silliman (1779–1864), the founder of the American Journal of Science, in Parker Cleaveland (1780–1858)9s Elementary treatise on mineralogy and geology. These fossils were found in Westfield, near Middletown, Connecticut. Shortly thereafter, Edward Hitchcock (1793–1864) also reported the discovery of fossil fishes in Sunderland, Massachusetts. Up to now, these specimens seemed to be lost or impossible to pinpoint in American museums. Some of them also found their way to France. In October 1818 and August 1821, Silliman sent several of these fossil fish slabs to the French geologist Alexandre Brongniart (1770–1847). Searches in French institutional paleontological collections that hold scattered parts of Brongniart9s collection made it possible to rediscover these historical fossils that went completely unnoticed so far. A specimen, identified as Redfieldius sp., from Westfield (Hartford Basin, Connecticut), is one of the very first authenticated fossil bony fishes ever reported in the United States. Eight slabs with “ichthyolites” (fossil fishes) collected in Sunderland (Deerfield Basin, Massachusetts) by Edward Hitchcock in or before April 1821 have also been rediscovered. Three of them contain type material (lectotype and paralectotype) of Semionotus fultus (Agassiz, 1833), the first scientifically named fossil fish from the Newark Supergroup. The other five slabs contain Semionotus sp. and Semionotus tenuiceps (Agassiz, 1835). This paper presents the historical context surrounding these early discoveries in the light of the correspondence between Hitchcock, Silliman and Brongniart. This study highlights an early example of transatlantic scientific exchange in geosciences at the beginning of the nineteenth century.

<EM>Bifurculapes</EM> Hitchcock 1858: a revision of the ichnogenus

Characters differentiating the arthropod trackway Bifurculapes from the similar ichnogenera Lithographus and Copeza include the position, arrangement and orientation of the tracks within the series. Of the five species of Bifurculapes originally described, only Bifurculapes laqueatus and Bifurculapes scolopendroideus are recognized herein; the other three ichnospecies are considered to be nomina dubia or junior subjective synonyms of Bifurculapes laqueatus. Two new specimens, recovered from the Early Jurassic East Berlin Formation of the Hartford Basin in Holyoke, Massachusetts, represent only the second unequivocal occurrence of the ichnogenus outside of the Deerfield Basin. Bifurculapes is currently known only from the Early Jurassic.

Sand pseudomorphs of dinosaur bones: Implications for (non-) preservation of tetrapod skeletal material in the Hartford Basin, USA

Early Jurassic tetrapod tracks are common in the Hartford and adjacent Deerfield Basins (Newark Supergroup) of Connecticut and Massachusetts, USA, but skeletal material is rare. Among the few examples is a set of several bones preserved as natural casts on the base of a slab of arkosic sandstone that probably derived from the Portland Formation of Middletown, Connecticut. This mode of preservation is otherwise unknown in the Hartford Basin, and examination of this specimen suggests a complex taphonomic history. The bones were fluvially transported and arranged in a v-shaped pattern as they were deposited on a muddy substrate. Longitudinal cracks, gouging, breakage, rounding, and invertebrate boring indicate significant alteration prior to preservation as casts. Furthermore, the boring represents the first record of osteophagy in the Hartford Basin. Details of the cast preservation, such as sediment rims that wrapped up and over some of the bones, suggest that the bones were dissolved in the subsurface prior to lithification of the overlying sand bed. The decrease in pH that led to bone dissolution probably resulted from the infiltration of naturally acidic rainwater. Root respiration and the decomposition of plants under oxidative conditions may have contributed as well. The depauperate skeletal fossil record of the Hartford Basin is attributable to dissolution under acidic and oxidative sediment conditions. These natural casts offer a unique view of the actions of bone dissolution as a taphonomic process. The lack of body fossils in similar aged deposits elsewhere may also be due to groundwater acidity.

Early Cretaceous Normal Faulting in Southern New England: Evidence from Apatite and Zircon Fission‐Track Ages

New apatite and zircon fission‐track (AFT, ZFT) ages from Mesozoic sediments and adjacent crystalline rocks from southern New England reveal age gradients from Middle Jurassic to Early Cretaceous. These gradients reflect the rotation of crustal blocks after the setting of the youngest AFT ages (∼140 Ma). The AFT ages of 168–98 Ma for 32 samples of Paleozoic metamorphic rocks east and west and within the Hartford Basin of Massachusetts and Connecticut indicate that unroofing in these regions occurred from Late Jurassic through Early Cretaceous. In both the Hartford Basin and rocks from crystalline terranes east of the basin, AFT ages show a regional trend of increasing age to the east, suggesting a down‐to‐the‐east rotation of ∼10° in each area. The ZFT ages from the Hartford Basin arkoses (167–238 Ma) and northern Bronson Hill (147–196 Ma) rocks support this gradient of eastward increase in AFT age. A south‐to‐north gradient of decreasing AFT age (139–107 Ma) for the sedimentary rocks in the Hartford and Deerfield Basins of Connecticut and Massachusetts suggests a 1°‐hinged uplift to the north that postdates the youngest AFT age of ∼100 Ma. Final juxtaposition of AFT ages across the eastern Border fault between the Hartford Basin and Bronson Hill terrane in Massachusetts and Connecticut indicates displacement younger than the youngest AFT ages of ≤100 Ma (Late Cretaceous). Thus, the age of the graben structure of the Hartford Basin is Cretaceous, and this structure cannot be cited as evidence that these basins are Early Mesozoic “rift” basins.

Palaeomagnetism, rock magnetism and geochemistry of Jurassic dykes and correlative redbeds, Massachusetts, USA

Jurassic diabase dykes, sills and sedimentary rocks in central Massachusetts were sampled for palaeomagnetic analysis. The intrusions fall into three of the chemical types for eastern North American diabases: high TiO2 quartz-normative (Holden); low TiO2 quartz-normative (Ware); and high Fe2O3 quartz-normative (Pelham–Loudville). The characteristic magnetizations in the majority of intrusive samples unblock between 550 °C and 580 °C, with Curie temperatures in a discrete interval between 556 °C and 580 °C. The dominant remanence in the diabases is carried by C1 to C3 oxidation-exsolved titanomagnetite occurring as euhedral grains, as fine needles or dust in the matrix, as devitrifed glass, and as fine magnetite-ilmenite-silicate symplectite. In some dykes, titanomagnetite was further modified by deuteric oxidation during post-magmatic cooling, creating titanomaghematite and/or a granulation of the magnetite. Palaeopoles for the three diabase groups are: Holden, 60.1°N, 80.5°E, A95 = 4.1°; Ware, 73.5°N, 85.8°E, A95 = 3.9°; and Pelham–Loudville, 65.3°N, 95.6°E, A95 = 4.1°. These data are combined with samples from two stratigraphic sections through the Early Jurassic part of the Sugarloaf Formation in the Deerfield Basin representing both fine-grained mudstones and coarser arkoses. These haematite-dominated rocks reveal several components of magnetization, a steep recent field direction, an intermediate secondary diagenetic overprint direction in both mudstones and arkoses, and a high-temperature shallow primary direction found only in the mudstones. Palaeopoles for the Sugarloaf Formation are: mudstones, 57.7°N, 81.3°E, A95 = 9.1°; and arkoses, 75.1°N, 131.6°E, A95 = 5.9°. Based on the new palaeomagnetic data reported here, the North American plate in the Middle Jurassic was at higher palaeolatitudes than indicated by the present North American apparent polar wander path.

Nature of a flood-basalt-magma reservoir based on the compositional variation in a single flood-basalt flow and its feeder dike in the Mesozoic Hartford Basin, Connecticut

The erosional remains of the Mesozoic Holyoke basalt in the Hartford, Pomperaug, and Deerfield basins of Connecticut and Massachusetts indicate an original flow volume of >1200 km3. Its feeder dike, which is about 50 m wide and 160 km long, can be traced down through 2 km of Mesozoic sediments and, as a result of faulting associated with basin formation, through an additional 6 km of Paleozoic metamorphic rocks. Chemical profiles through the distal and proximal parts of the flow and through the dike at depths of 2, 4, and 8 km provide sequential samples of the magma that rose during this one eruptive event. The flow and dike have restricted compositions that indicate saturation with olivine, augite, and plagioclase at depth. The flow consisted largely of a liquid at the pigeonite reaction point. Dike compositions can be modeled as mixtures of this liquid with up to 24% crystals of plagioclase, augite, and olivine. The dike compositions indicate equilibration with these minerals at 3.8 kbar. This pressure corresponds to a depth of 12.2 km, which is believed to have been the depth of the brittle/ductile transition in the crust at the time. This transition appears to be the only reasonable barrier that could have caused ponding of the magma at the mid-crustal level. The Holyoke liquid is interpreted to have segregated from a compacting crystal mush following 30% crystallization of the magma in this mid-crustal reservoir. Eruption of the basalt exhausted the supply of segregated liquid, and when the remaining crystal mush began to rise in the dike, the average density of the magma column increased until it matched the average density of the intruded crust, and the eruption ended. By analogy with the differentiation that took place in the solidifying Holyoke flow on the surface, the mid-crustal magma reservoir is estimated to have had a volume of at least 12,000 km3. The magma in this chamber must have come from a still deeper chamber, because it was too fractionated to have come directly from a mantle source.

Type material of the type species of the classic theropod footprint genera Eubrontes, Anchisauripus, and Grallator (Early Jurassic, Hartford and Deerfield basins, Connecticut and Massachusetts, U.S.A.)

ABSTRACT The classic Early Jurassic age theropod footprints Eubrontes giganteus, Anchisauripus sillimani, and Grallator parallelus were established by Edward Hitchcock in 1836–1847 and are the type ichnospecies of their respective ichnogenera. We identify, describe, and figure the type specimens in detail for the first time since they were named. We also figure and describe the other elements of the type series as well as specimens mistakenly thought to be the types. All of the tracks come from cyclical lacustrine and marginal lacustrine to fluvial strata from an interval spanning about one million years in the Early Jurassic age Meriden and Agawam groups of the Hartford and Deerfield basins of Connecticut and Massachusetts. Based on osteometric comparisons with skeletal material, these three ichnospecies were most likely made by theropod dinosaurs, as usually assumed. Although treated here as distinct ichnogenera, it is possible that their major proportional differences derive from allometric growth with individuals of several related species in one genus or even within one species of trackmaker. The rigorous establishment of these classic ichnological taxa forms a basis for more wide ranging studies of theropod diversity in the early Mesozoic.

Timing and temperature of decollement on hydrocarbon source rock beds in cyclic lacustrine successions

The generation of hydrocarbons causes lubrication of source rock bedding planes which can enhance deformation during basin subsidence and subsequent tectonic events. Deformation includes decollement, i.e. gravitational sliding of rocks above the lubricated horizon. In cyclic sequences, such as occur in many lacustrine basins, decollement is generally restricted to the organic-rich beds of the cycle. Case studies in lacustrine successions in the Devonian Orcadian Basin, Scotland, and the Triassic–Jurassic Hartford–Deerfield Basin, USA, show that movement of material associated with the decollement surface occurred in the current down-dip direction. These extensional basins experienced rapid subsidence and a high heat flow such that hydrocarbon generation, and therefore decollement, occurred early in the basin histories. During extension, half-graben rotation ensured that the beds were dipping during hydrocarbon generation, facilitating decollement. Inversion of the Orcadian Basin reactivated decollement surfaces, involving thrust motion in some cases. Minerals precipitated in tension cavities associated with decollement yield fluid inclusion homogenization temperatures in the ranges 96–139°C and 85–96°C for the Orcadian and Hartford–Deerfield basins, respectively. These data are consistent with burial into the oil window at depths of between 1.5 and 2.0 km.

Edward Hitchcock, Fucoides, and the Ichnogenus Scoyenia

Historical research conducted on the scientific contributions of Edward Hitchcock (1793-1864) has documented the first complete published descriptions and illustrations of abundant Early Mesozoic nonmarine burrows from the Deerfield Basin, Massachusetts [Newark Supergroup] which of late have been called Scoyenia White 1929. Although Hitchcock believed that he was describing fossilized algae or seaweeds (fucoids), his observations revealed nearly all the diagnostic characteristics of the ichnogenus; in particular, the meniscate nature of its backfilling. Today, most of his original specimens have been relocated and examined. Probable reasons for the subsequent obscurity of his findings are explored, along with rediscoveries of the same trace fossil by later generations of paleontologists.

Paleomagnetic correlation of Newark Supergroup volcanics

Three Lower Jurassic volcanic sequences are present in the Deerfield, Hartford, and Newark basins of eastern North America. Volcanics from the Deerfield and Newark basins display similar magnetic directions that also agree with magnetizations from associated Lower Jurassic intrusives. The intermediate volcanic sequence, including the Deerfield basalt, the Holyoke basalt, and the base of the Second Watchung basalt, yields anomalous directions that differ by more than 30{degrees} from the nominal Early Jurassic direction. These anomalous directions record a short-lived geomagnetic secular variation event that provides a chronostratigraphic marker. The simplest interpretation of the paleomagnetic and geochemical data is a one-to-one correspondence between successive volcanic units of the Hartford and Newark basis, a correlation that agrees with a previous scheme based upon geochemical inferences. Our data suggest that initiation of the second eruptive phase was synchronous over the 300 km from the Deerfield Basin to the Newark Basin. Reevaluation of the widely quoted N1 Early Jurassic paleomagnetic pole for North America indicates that the 72 virtual geomagnetic poles from which it was originally derived are not all independent observations. The N1 reference pole probably represents 7 independent samples of the geomagnetic field, each of which averages at best a small amountmore » of geomagnetic secular variation. As a consequence, the N1 paleomagnetic pole may not represent the time-average paleofield.« less

Lacustrine Strata of Early Jurassic Age, Hartford and Deerfield Rift Basins, Massachusetts and Connecticut: Deposition, Maturation of Black Mudstones, Sandstone Diagenesis, and Hydrocarbon Occurrences: ABSTRACT

Lacustrine cycles occur in the 100-m Shuttle Meadow, 170-m East Berlin, and lower part of the 1,200-m Portland Formations in the Hartford basin and in the 600-m Turners Falls Sandstone in the Deerfield basin. Eleven exposed cycles range in thickness from 3 to 10 m. Black mudstones are mostly 1-2 m thick, deposited in the deeper parts of oligomictic perennial lakes. Gray sandstones accumulated on delta lobes, fan deltas, and from sheetfloods that spread across the valley floor to cover exposed lacustrine littoral muds. Both rift-basin fills are dominated by alluvial-fan, fluvial, and playa red beds. The lacustrine sandstones are arkoses and lithic arkoses (72 modal analyses). Omitting minor cements, diagenetic events are (1) compaction, (2) quartz and albite overgrowths with albitization of detrital plagioclase, (3) dolomite and ferroan dolomite cements, and (4) hydrocarbon migration with creation of secondary porosity. Consistently large intergranular volumes in the lacustrine sandstones, as high as 40%, suggest that cementation began prior to significant compaction. Porosity in the sandstones ranges from 0 to 11%, averaging 2%. Organic geochemical data for black mudstones in the East Berlin, Portland, and Turners Falls Formations, combined with published and USGS open-file data, show that organic richness and oil pronenessmore » increase southward in the Hartford basin whereas thermal maturity increases northward. Oil generation has occurred in the East Berlin Formation, as evidenced by relatively large amounts of extractable bitumen, high-molecular-weight hydrocarbons, and hydrocarbons present in the sandstones. The Deerfield basin is overmature for oil.« less

Hartford and Deerfield Basin Framework Mineralogies: Independent Evidence for Provenance, Current Directions, and Tectonic History: ABSTRACT

Hartford and Deerfield Basin Framework Mineralogies: Independent Evidence for Provenance, Current Directions, and Tectonic History: ABSTRACT