Abstract The Canadian Arctic–Beaufort Sea Rifted Margin (CARM) Tectono-Sedimentary Element (TSE) is located on the continental shelf and slope that lie to the west of the Canadian Arctic Archipelago and to the north of the Mackenzie Delta. The TSE comprises the rift succession deposited on the eastern and southern margins of the Amerasia Basin, coincident with the opening of this basin. The TSE strata range in age from the latest Triassic (Rhaetian) to Early Cretaceous (Albian). A major unconformity marks the base of the TSE, with underlying rocks consisting of moderately to highly deformed Proterozoic and Lower Paleozoic rocks that are regarded as basement. The TSE is overlain by the Canadian Arctic Prograded Margin (CAPM) TSE, with the boundary being a significant unconformity in landward areas. Well data are limited to the Beaufort–Mackenzie area, and reflection and refraction seismic data indicate that the succession is up to 4 km thick. The TSE is divided into four structural domains, with deformation increasing to the north. The Beaufort–Mackenzie Domain is dominated by extensional structures, with later contractional structures present in its western portion. The Southern Domain is extensional and characterized by normal faults with tilted fault blocks. The structure of the Central Domain is similar to that of the Southern Domain but may include broad folds formed during the Paleogene Eurekan Orogeny. The succession in the Northern Domain is likely to be strongly folded and cut by thrust faults of the Eurekan Orogeny. Cretaceous extrusive and intrusive basic rocks, related to magmatism in the northern Amerasia Basin, are present in both the Central and Northern domains. Petroleum source rocks, of both lacustrine and marine origin, may be present in the Jurassic portion of the succession and marine shales in the Lower Cretaceous succession. The potential for structural and stratigraphic traps in widespread sandstone units of alluvial fan to marine slope origin is high. The remote location of the TSE, however, makes it likely that it will not be a target for petroleum exploration in the foreseeable future.

Abstract The Canadian Arctic Prograded Margin Tectono-Stratigraphic Element (TSE) is located on the continental shelf and slope, which lie to the NW of the Canadian Arctic Archipelago. The TSE comprises a post-rift succession deposited on the eastern margin of the Amerasia Basin, and the strata range in age from Late Cretaceous to Pleistocene. Over much of the TSE, a major unconformity marks the base of the succession, and the underlying strata vary from Jurassic to Lower Cretaceous strata of the Canadian Arctic Rift Margin TSE to older Upper Paleozoic–Triassic strata of the Sverdrup Basin Composite Tectono-Sedimentary Element. Sparse reflection and refraction seismic data indicate that the succession can be more than 10 km thick. The TSE is divided into three structural domains with deformation increasing to the NE. The Southern Domain is extensional and is characterized by listric growth faults with rollover anticlines and tilted fault blocks. The pre-Oligocene portion of the Central Domain is deformed by broad folds with extensional faults in the younger strata. The pre-Oligocene succession in the Northern Domain is likely to be strongly folded and cut by thrust faults of the Eurekan Orogeny with extrusive and intrusive igneous rocks occurring in the Upper Cretaceous strata. Petroleum source rocks, as well as abundant reservoir and seal strata, occur throughout the TSE, indicating good potential for the presence of petroleum resources. The remote and environmentally sensitive location of the TSE, however, makes it likely that it will never be a target for petroleum exploration.

Abstract The Sverdrup Basin Composite Tectono-Sedimentary Element (CTSE) covers 210 000 km 2 in the Canadian Arctic Archipelago. The CTSE was initiated in the Early Carboniferous by rifting of highly deformed Early Paleozoic strata and contains a maximum of 15 km of Carboniferous–Eocene strata. Eight phases of basin development have been recognized, with each being characterized by a specific combination of tectonic and depositional regimes. The phases are separated by intervals of uplift and tectonic reorganization, and each resultant first-order sequence is regarded as a separate TSE. Carbonate sedimentation was dominant in the Late Carboniferous and Early Permian, with clastic sedimentation becoming more common in the Middle Permian. Source areas lay to the east, south and north. In the Triassic, clastic sedimentation rates increased; and by the end of the Triassic, the central basin was filled. A shallow seaway was present throughout the Jurassic. In the Early Cretaceous, subsidence rates and clastic supply increased significantly, and basic volcanism occurred over most of the CTSE. Subsidence rate, sediment supply and volcanism decreased in the Late Cretaceous. The basin was progressively deformed in the Paleogene (Eurekan Orogeny), with local foreland deposits reaching 3 km. Seventeen oil and gas fields have been discovered on salt-cored, Eurekan anticlines. A combination of stratigraphic and structural traps, involving Triassic–Jurassic strata, has the greatest potential for future hydrocarbon discoveries.

ABSTRACT The Tanquary High is a positive tectonic feature that was identified on the southern margin of the far northeastern portion of Sverdrup Basin. A sequence stratigraphic analysis of the Triassic succession of northern Ellesmere Island, involving 27 measured sections and one well section, has allowed the geometry and evolution of the high in the Triassic to be elucidated. The Triassic succession occurs within five second-order sequences, and each sequence boundary reflects the occurrence of a tectonic episode that included basin margin uplift and basinward movement of the shoreline. The Tanquary High was uplifted during these tectonic episodes, which occurred in the latest Permian, latest Early Triassic, latest Middle Triassic, latest Carnian, and latest Norian. Each sequence is truncated toward the crest of the high where Rhaetian strata now overlie Cambrian strata. Isopach and facies data for each sequence reveal that, at the times of maximum uplift of the Tanquary High, the subaerially exposed part of the high extended 100–150 km down its northwest-trending axis and up to 150–200 km down each flank. Rapid subsidence completed each tectonic episode and initiated the development of a new sequence. The Tanquary High was completely drowned at these times. It is hypothesized that the tectonic episodes were generated by changes in horizontal stress fields driven by plate tectonic reorganizations. The facies and isopach maps of the latest Triassic to early Early Jurassic (Rhaetian-Sinemurian) second-order sequence demonstrate that the Tanquary High ceased to exist following the first order, latest Norian sequence boundary. A complete reversal of source areas and the initiation of the Amerasia rift basin coincided with the demise of the Tanquary High.

The goal of this study is to catalogue all the large scale, tectonically-generated sequence boundaries which punctuate the Phanerozoic stratigraphy of the North American Arctic and to determine the frequency and possible origin of the interpreted tectonic episodes which gave rise to the boundaries. This study is feasible because, over the last 40 years, the Phanerozoic succession of the North American Arctic, both on the surface and in the subsurface, has been intensely studied in various sedimentary basins with modern basin analysis techniques including sedimentology, sequence stratigraphy and biostratigraphy.

Multiple Sclerosis is an autoimmune disease in which the immune system causes damage to tissues in the central nervous system. The disease results from both genetic and environmental factors. Studies of identical twins demonstrate that MS develops only in genetically susceptible individuals due to one or more environmental influences. The epidemiology of MS provides a number of important constraints for the interpretation of the environmental factor which can be regarded as the main cause of MS. The disease has a very uneven geographic extent and occurs mainly in USA, Canada,western Europe, New Zealand and Australia where prevalences are generally greater than 50 per 100,000 population. In these areas there is a noticeable north/south gradient with MS being more prevalent in higher latitude, temperate regions. Also within individual countries there are significant differences in MS prevalence and incidence. Other important constraints are the sudden increase in prevalence in the Faroe Islands following World War II occupation by British troops and the fact that residency in Hawaii increases the risk of MS for those of Japanese descent while simultaneously decreasing the risk for Caucasians. Studies have also shown that MS cannot be transmitted by person to person contact or by blood transfusion. Finally MS is a modern disease which appeared about175 years ago. The prevalence has steadily increased from that

Preface This essay was submitted in January, 2000 to the Institute of Medicine (IOM) Committee on Multiple Sclerosis: Current Status and Strategies for the Future which was commissioned by the National Multiple Sclerosis Society (NMSS). The purpose of the essay was to convince the Committee to include a recommendation for research into the likely role that diet plays in MS onset and progression.

Sequence stratigraphy is a stratigraphic discipline in which the defined stratigraphic surfaces represent either breaks in deposition or changes in depositional trend. Two approaches for defining sequence stratigraphic surfaces and units have evolved, with one being inductive and the other deductive. The empirical, inductive approach defines surfaces based on observable, physical characteristics. Five surfaces, subaerial unconformity (SU), unconformable shoreline ravinement (SR-U), slope onlap surface (SOS), maximum regressive surface (MRS), and maximum flooding surface (MFS), are used to define inductive sequence units and to construct a correlation framework. Two different types of sequences (depositional T-R, genetic stratigraphic) and two systems tracts (transgressive systems tract, regressive systems tract) are employed in the inductive approach. In contrast, the deductive approach defines sequence stratigraphic surfaces in terms of theoretical events on a base-level curve (e.g., start base-level fall). Three deductive surfaces (SU, MRS, and MFS) used for unit definition and correlation are the same as those employed by the inductive approach. Two surfaces, not recognized in the inductive approach, are also used to delineate units and for correlation. Notably, both are chronostratigraphic surfaces which display no diagnostic physical characteristics. These surfaces include the basal surface of forced regression (BSFR), the depositional surface at the start of base-level fall, and the correlative conformity (CC), the depositional surface at the start of base-level rise. A sequence is defined as a succession of strata deposited during a full base-level cycle and associated change in accommodation or sediment supply. Recognition of the five surfaces has allowed the definition of four types of sequences (depositional sequence type 1 and 2, T-R, genetic stratigraphic), with each type being divided into four systems tracts (lowstand, transgressive, highstand, and falling stage). The decision as to what approach to use—inductive or deductive—depends on the robustness of the available data and whether the BSFR and CC can be recognized with reasonable objectivity and consistency over the study area. Caution must be exercised to avoid the pitfall of trying to force fit data into the deductive approach by interpreting an inappropriate surface (e.g., facies change) as either the BSFR or CC. In many situations, especially when seismic data are not available, it is not possible to recognize and correlate the BSFR and/or the CC with objectivity. In these cases, the inductive approach is required for unit delineation and correlation.

The Late Triassic was the time of the Early Cimmerian and Indosinian orogenies that closed the Paleotethys Ocean, which occurred earlier in the Alpine-Carpathian-Mediterranean area, later in the Eastern Europe-Central Asia and latest in the South-East Asia. The Indochina Southeastern Asian and Qiangtang plates were sutured to South China. The new, large Chinese-SE Asian plate, including North and South China, Mongolia and eastern Cimmerian plates, was consolidated by the end Triassic, leaving open a large embayment of Panthalassa, known as Mongol-Okhotsk Ocean, between Mongolia and Laurasia,. The Uralian Orogeny, which sutured Siberia and Europe continued during Late Triassic times and was recorded in Novaya Zemlya. The onset of Pangaea break-up constitutes the main Late Triassic extensional event. Continental rifts originating then were filled with clastic deposits comprising mainly red beds. The pulling force of the north-dipping subduction along the northern margin of Neotethys caused drifting of a new set of plates from the passive Gondwana margin, dividing the Neotethys Ocean. Carbonate sedimentation dominated platforms on the Neotethys and Paleotethys margins as well as the Cimmerian microplates. Synorogenic turbidites and postorogenic molasses were associated with the Indosinian orogeny. The late stages of the Uralian orogeny in Timan-Pechora, Novaya Zemlya and eastern Barents regions filled the foreland basin with fine-grained, molasse sediments. Siliciclastics were common in the Siberia and Arctic regions. The widespread, large magnitude, base-level changes of the Late Triassic are interpreted as an expression of relatively rapid and substantial changes in the horizontal and vertical stress fields that affected the Pangaea supercontinent. Such stress changes may be due to abrupt changes in the speed and/or direction of plate movements, which episodically affected Pangaea.

Detrital zircon U-Pb ages are used to provide constraints on the geologic evolution of the sediment source area(s) north of the Sverdrup Basin from the middle Permian to Late Triassic. Previous research on fades relationships and sediment progradation patterns of late Paleozoic and Triassic strata from the northern portion of Sverdrup Basin indicate that substantial sediment was derived from north of the basin. Utilizing LA-ICP-MS U-Pb geochronology we have analyzed detrital zircons from these northerly derived strata, including sandstones of four LateTriassic (Norian) outcrop samples the northeast Sverdrup Basin, and two Triassic (Olenekian and Carnian) and two Permian (Roadian and Wordian) samples from wells in the northwestern Sverdrup Basin.The samples from northwestern Sverdrup Basin contain abundant Early Mississippian (350 Ma) to Early Ordovician (460 Ma), late Cambrian (500 Ma) to Cryogenian (650 Ma), and early Tonian (960 Ma) to Orosirian (2050 Ma) detrital zircon. The detrital zircon ages from these samples are similar to zircon age components of Late Devonian siliciclastic strata of the Franklinian foreland basin, and we suggest a similar source area, a low-lying landmass north of the Sverdrup basin, which included extensive Devonian foreland basin strata.The U-Pb detrital zircon age components of northerly-derived Late Triassic strata of northeastern Sverdrup Basin samples are similar to the Permian and Triassic Northwestern Sverdrup Samples, but also contain a substantial age component of Triassic (201 Ma) to Middle Mississippian (340 Ma) detrital zircons, suggesting an additional source area. The only well documented source for such zircons in the Arctic region is the Ural Orogen. Consequently, it is postulated that, in the Late Triassic, sediment was transported similar to 1500 km from the northern Urals, across the northern landmass, all the way to the shoreline of northeastern Sverdrup Basin. (C) 2016 Elsevier B.V. All rights reserved.

Quantitative palynology of the marginal marine and deltaic-fluvial Isachsen Formation of the Sverdrup Basin, Canadian Arctic, provides insight into high latitude climate during much of the Early Cretaceous (Valanginian to early Aptian). Detrended Correspondence Analysis of main pollen and spore taxa is used to derive three ecological groupings influenced by moisture and disturbance based on the botanical affinities of palynomorphs: 1) a mixed coniferous assemblage containing both lowland and upland components; 2) a conifer-filicopsid community that likely grew in dynamic lowland habitats; and, 3) a mature dry lowland community composed of Cheirolepidiaceans. Stratigraphic changes in the relative abundance of pollen and spore taxa reflect climate variability in this polar region during the ∼20 Mya history of the Isachsen Formation. The late Valanginian was relatively cool and moist and promoted lowland conifer-filicopsid communities. Warming in the Hauterivian resulted in the expansion coniferous communities in well-drained or arid hinterlands. A return to relatively cool and moist conditions in the Barremian resulted in the expansion of mixed lowland communities. This work demonstrates the utility of a multivariate statistical approach to palynology to provide insight into the composition and dynamics of ecosystems and climate of high latitude regions during the Early Cretaceous.

This study summarizes the results of petrographic and geochemical analysis of Middle Triassic strata from the Sverdrup Basin in the Canadian Arctic. In this work, we investigate the distribution and depositional conditions of dispersed organic matter (OM) as a preliminary step towards understanding the potential of this stratigraphic interval as an unconventional reservoir. Closely-spaced samples from three Middle Triassic cores (southern margin, basin centre, northern margin) are analyzed using Rock-Eval analysis, inductively coupled plasma-mass spectrometry (ICP-MS), and organic petrology. Total organic carbon (TOC) ranges between 0 and 4.8wt.%, with the most organic-rich interval having a median TOC value of 3.2wt.%. Kerogen type varies from Type II to Type III throughout the sampled intervals. Samples from near the top of the regressive systems tract of the Anisian 3rd order sequence (basin centre) and near the middle of the Ladinian 3rd order sequence (southern margin) contain predominantly reworked, highly oxidized macerals and abundant coarser clastic material. Results support oxic to suboxic depositional conditions for these intervals. By contrast, samples from near the base of regressive systems tracts of both sequences (basin centre and northern margin) have the highest amounts of TOC (i.e., median=3.2wt.% and 1.4wt.%), containing retained migrabitumen and abundant labile primary kerogen, respectively. The base of the Ladinian regressive systems tract near the basin axis was deposited under anoxic conditions and can be considered a prospective shale oil interval. Small-scale cyclic clastic influx episodes along the northern margin of the basin show changes from oxic to suboxic bottom waters. These cycles may be considered evidence for northerly-derived sediment from Crockerland during the Middle Triassic. The results and interpretations of this study can be applied to analogous fine-grained successions in other basins to better understand their unconventional reservoir potential.

The Lower Cretaceous Isachsen Formation is a widespread, siliciclastic succession up to 1.4 km thick that records the northwestward progradation of fluvio-deltaic environments into the Sverdrup Basin in the Canadian Arctic. Although the Isachsen Formation is a prominent unit with proven oil and gas reserves, detailed outcrop descriptions of its sedimentology and stratigraphy, and correlation of these features to subsurface data are rare. We examined outcrop exposures of the Isachsen Formation on Ellef Ringnes Island in the province of Nunavut in the Canadian Arctic in order to document and interpret the sedimentology and stratigraphy of this unit in the central portion of the Sverdrup Basin. Interpretations are based on observations from over 5000 m of measured stratigraphic sections, local mapping of facies contacts, palynology, and sandstone petrography. Deposits of the Isachsen Formation on Ellef Ringnes Island can be divided into six broadly-defined fades associations that record deposition in braided-fluvial, meandering-fluvial, floodplain, tidally-influenced fluvial, shoreface, and offshore environments. Sandstones within the Isachsen Formation are typically quartzose, commonly with compositions of >90% well-rounded, monocrystalline quartz. Although the sedimentary details between outcrop locations vary, a generalized stratigraphic trend is present within the Isachsen Formation. Where exposed, the base of the unit consists of marginal marine sandstones abruptly overlain by braided stream deposits, which grade into mudstone-rich, meandering-fluvial and floodplain deposits. These nonmarine deposits are overlain by a thin marine mudstone (Rondon Member), which is in turn overlain by marginal marine sandstone and fluvial deposits. The uppermost portion of the Isachsen Formation records a transgression and is overlain by marine mudstones of the Christopher Formation. The stratigraphic succession of the Isachsen Formation in outcrops correlates to data from nearby hydrocarbon exploration wells. Stratigraphically, the Isachsen Formation on Ellef Ringnes Island represents a regressive transgressive sequence, but contains within it two higher-order regressive transgressive sequences, which is consistent with observations from elsewhere in the Sverdrup Basin. The detailed descriptions of fades within the Isachsen Formation on Ellef Ringnes Island and their correlation to subsurface data can be extrapolated to other parts of the Sverdrup Basin where data are lacking. (C) 2014 Elsevier Ltd. All rights reserved.

Exceptional exposures of a High Arctic Cretaceous sedimentary record were studied at Glacier Fiord, Axel Heiberg Island. The succession reveals a complex Aptian to Santonian paleoenvironmental history of the Sverdrup Basin that documents several global events. Foraminiferal faunas in combination with rare macrofossil occurrences permit the distinction of nine zones that facilitate biostratigraphic correlations to other High Arctic locales, the Beaufort Mackenzie Basin and the Western Interior Sea. The depositional environment as exposed in the Christopher, Hassel, Bastion Ridge and Kanguk formations changed frequently from a shelf to a shoreface setting. Most sequence boundaries appear to be conformable where shoaling reached lower shoreface levels without subaerial exposure. An exception is the top of the Hassel Formation, correlated here with the Albian/Cenomanian disconformity where a paleosol developed on top of an upper shoreface environment. Transgressive/regressive sequences at Glacier Fiord correspond well with globally recognized transgressive/regressive mega cycles. The lower Christopher Formation shows frequent glendonite beds that attest to the Late Aptian/Early Albian cooling event. The required alkaline conditions for glendonites preserved the only calcareous faunule in the succession. Siliceous microplankton are assumed to be taphonomically removed due to deep burial. The Middle to Late Albian oceanic shelf conditions appeared to be most hospitable and foraminifera grew large tests. In the early Cenomanian and lower Bastion Ridge Formation, benthic species disappear. This sudden loss is interpreted as a consequence of nearby volcanic activity related to the Strand Fiord Formation and basin restriction. This is followed by a period of increased preservation of organic carbon and a distinct increase in marine productivity marking the OAE 2 in the Polar Sea straddling the Cenomanian/Turonian boundary. This interval is expressed in a platy shale, devoid of microbioturbation, but characterized with a repopulation event where the low oxygen tolerant genus Trochammina is the dominant component. The Upper Turonian to Santonian interval of the Kanguk Formation reflects shelf conditions that supported mostly rich benthic assemblages, but have at times minute tests as a response to oxygen depletion.

The Middle Triassic Murray Harbour Formation is an organic-rich shale and siltstone unit located in the Sverdrup Basin in Arctic Canada. In this study, the depositional environment and preliminary hydrocarbon potential of the unit are examined using dispersed organic matter within the established sequence stratigraphic framework. Core samples from wells drilled at three different locations within the basin and intersecting different stratigraphic positions in the Murray Harbour Formation are analysed using Rock Eval pyrolysis and organic petrology. Median total organic carbon values range from 0 to 4.8 wt% and T max values indicate that samples from the wells located on the inner marine shelf, along the northern and southern margins of the basin, are thermally immature. The well located on the outer marine shelf, in the deeper, central part of the basin, is thermally mature and within the oil generation window. The most organically lean samples are taken from the top of regressive systems tracts and contain predominantly reworked, highly oxidized inertinitic and vitrinitic material. Bioturbation of these samples indicates oxygenated bottom waters at the time of deposition, preventing significant preservation of organic material. The most organically rich samples are taken from the base of regressive systems tracts, when the basin experienced near-maximum transgression.

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 (<7 km) within the basin and source terrane thermal–tectonic evolution. Paleocurrent data, sediment composition, εNd values and detrital zircon U–Pb ages from previous studies indicate Middle to Upper Devonian strata of the Franklinian Basin are derived from two principal sediment source regions, the East Greenland Caledonides and a northern continental landmass (referred to as Crockerland). However, ZHe ages indicate these two distinctly different source regions experienced coeval exhumation in the Silurian Period. ZHe ages from Crockerland-derived sediment provide evidence that this landmass, which collided with northern Laurentia during the Ellesmerian Orogeny, was associated with the Caledonian Orogen. AHe ages from Middle to Upper Devonian strata are younger than depositional ages, indicating the AHe ages are at least partially reset since deposition and hence record information about exhumation of the strata and not the sediment source region. Dispersion of AHe single-grain ages from Middle Devonian strata along the southeastern margin of the basin suggest complex initial single-grain characteristics and may indicate long residence time in the He partial retention zone. AHe ages from Upper Devonian samples from the western margin of the basin are also dispersed but indicate the region experienced protracted exhumation from 330 to 190 Ma during early stages of Sverdrup Basin development. AHe ages from Middle Devonian samples from the western margin of the basin suggest two potential periods of prolonged exhumation in Early Cretaceous (Valanginian to Aptian) and Late Cretaceous (Campanian) times. These ages partially coincide with regional erosional or nondepositional events followed by deposition of major clastic units in the adjacent Sverdrup Basin.

New detrital zircon uranium–lead (U–Pb) ages and initial epsilon hafnium (εHf(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 εHf(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 εHf(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.