Ellesmerian Orogeny Research Articles

A Framework for North Slope Seminar II: ABSTRACT

This meeting focuses on a province with enormous potential for fuels and minerals. Oil reserves approach 10% of the total oil already produced in the rest of the country. Estimated coal resources could store a thousand times the 70-80 quads of energy the U.S. uses every year. Potential yields of silver, lead, and zinc range from 10 to 100% of the amounts produced domestically since the middle of the 19th century. Prospects for copper are also large. The province is dominated by the east-trending Brooks Range, whose structures formed during the late Mesozoic Brookian orogeny and are now being shortened longitudinally. Flanking basins succeeded the uplift; the northern one is bounded by a passive continental margin. Early in the orogeny, a relatively thin early Paleozoic through Jurassic megasequence of clastic-wedge, carbonate, and siliceous sediments was telescoped into a fivefold stacking of allochthons and beneath allochthons of volcanic and mafic-ultramafic rocks. The greater than 500-km breadth of sialic crust that had underlain the allochthons disappeared. At about the same time, the Arctic Ocean basin replaced the northern provenance. A mid-Paleozoic sialic source area on the opposite margin of the megasequence disappeared y the end of the Carboniferous and near the beginning of siliceous deposition. Basement beneath the North Slope part of the mega-sequence was created when the Devonian Ellesmerian orogeny added to the crust the late Precambrian to early Paleozoic clastic, carbonate, and volcanic rocks of an older megasequence. The northern successor basin accumulated large amounts of coal. Truncation and sealing of potential reservoir rocks on replacement of the northern landmass led to huge pools of hydrocarbons. Late Paleozoic rocks in the lowest allochthon host stratabound base-metal deposits. A narrow belt of reportedly Devonian shallow-seated felsic rocks contain deposits of copper. John Maher foresaw the benefits that the first North Slope seminar has provided. That precedent and developments during the past 15 years promise similar benefits from this meeting. End_of_Article - Last_Page 680------------

Late Paleozoic to Cenozoic Reconstruction of the Arctic: ABSTRACT

The plate tectonic evolution of the Arctic is reassessed in the context of the known histories of the North Atlantic and North Pacific Oceans, and of the tectono-stratigraphic development of the lands around the Arctic Ocean. Computer map-drawing facilities were used to provide geometrical constraints on the reconstructions, which are presented in the form of eight palinspastic maps. Stratigraphic similarities among presently dispersed continental areas identify fragments of a former plate. Collision of this plate with the Euramerican plate was the cause of the Late Devonian Ellesmerian orogeny. In later Paleozoic time, the Siberian continent also joined Pangea by collision with the combined Barents and Euramerican plates along the Urals-Taymyr suture. The Mesozoic-Cenozoic history of the Arctic is concerned with the fragmentation and dispersal of the former Barents plate, as well as the accretion of new continental fragments from the Pacific. Of the major basins of the present-day Arctic Ocean, the Eurasia basin formed contemporaneously with the North Atlantic Ocean and is still spreading, while the earlier opening of the Canada basin was largely connected with events in the Pacific. The Canada basin formed by the separation of northern Alaska from the area now occupied by the Alpha Ridge. Initial rifting in the Late Jurassic was contemporaneous with the earliest major accretionary events in eastern Siberia and the northwestern Cordillera of North America. An Early to mid-Cretaceous age for the main phase of spreading is confirmed by the age-depth relationship for the floor of the Canada basin. After this time, the Canada basin formed part of the North Atlantic plate, and subsequent movements related to the opening of the orth Atlantic and Eurasia basins were taken up within Siberia and the Bering Sea area. The history of the latter is not yet clear for times earlier than the late Eocene--the earliest time for which it is possible to make a geometrically realistic reconstruction of that area. Earliest stages of spreading in the northern North Atlantic caused the initial separation of Greenland from North America. The Eurekan orogeny in the eastern Canadian Arctic is a local result of this spreading. Palinspastic restoration of the eastern Canadian Arctic Islands is required to fill the gap otherwise left in reconstruction of that area. The Eurasia basin opened contemporaneously with the Norwegian Sea and thus entirely postdates the Canada basin. Geometrical constraints suggest that the Makarov basin, between the Alpha and Lomonosov Ridges, formed during the Eocene. End_of_Article - Last_Page 679------------

Evolution of the early Paleozoic deep-water basin of north Greenland—Aulacogen or narrow ocean?

A major lower Paleozoic deep-water sequence is exposed for more than 800 km along the coast of north Greenland. The maximum preserved width of the basin is about 200 km, and the thickness of the sedimentary sequence may reach 8 km. Nine evolutionary stages in basin evolution are recognized, each characterized by distinct sedimentary facies and structural style of the shelf-basin boundary: (1) the oldest sequence of unknown age is so deformed that inferences about the depositional environment are precluded; (2) late Precambrian(?)-Early Cambrian incipient basin; (3) Early Cambrian narrow turbidite basin; (4) Middle Cambrian-Ordovician basin expansion and initial starvation; (5) latest Ordovician-Early Silurian longitudinally filled turbidite basin; (6) Middle Silurian basin expansion and starvation; (7) Middle-Late Silurian wide turbidite basin; (8) Middle-Late Silurian Caledonian thrusting and conglomerate deposition; and (9) probably latest Silurian megasliding and advance of the Caledonian front. The basin evolution that came to an end during the mid-Paleozoic Ellesmerian orogeny was punctuated by events related to the closure of the Iapetus ocean and formation of the Caledonian mountain belt to the east. The basin may have been fully ensialic and formed during the early rifting stages preceding back-arc spreading, or it may have reached a narrow ocean stage. At present, however, we are inclined to favor an interpretation of the basin as being an aulacogen extending deeply into an old continent at a right angle to the Caledonian orogenic front to the east.

Fold belts and metamorphic zones of northern Ellesmere Island and North Greenland

The Innuitian tectonic province extends in its eastern part through northern Ellesmere Island and across North Greenland. The mid- to late Palaeozoic Ellesmerian orogeny produced NE-SW to E-W trending fold belts and metamorphic zones in the strata of the Franklinian geosyncline. The late Cretaceous-Tertiary Eurekan orogeny deformed the Carboniferous-Tertiary rocks of the Sverdrup and Wandel Sea Basins, and overprinted or accentuated the older structures of the Franklinian geosyncline. The locations of the south limit of Ellesmerian folding, and of fold belts of comparable style, deformation intensity and metamorphic grade on the two sides of the Nares Strait lineament are consistent with models of left-lateral displacement in the range 0-50 km. Models of displacement greater than 50 km introduce increasingly improbable mismatches of fold belts and metamorphic zones. The Innuitian tectonic province extends in its eastern part through northern Ellesmere

Evolution of sedimentary basins in the Canadian Arctic

Since middle Proterozoic time, two long-lasting phases affected the Canadian Arctic Archipelago, each forming a different sedimentary basin. The Franklinian Basin, which was floored by continental or quasi-continental crust, received 10 km or more of clastic, carbonate and volcanic rocks from the mid-Proterozoic to Devonian. Internal parts of the basin were deformed, intruded and metamorphosed locally, and external parts were folded and thrust cratonward by compressional episodes of the Ellesmerian Orogeny, which culminated in the late Devonian. This marked the end of a phase, at which time the entire region may have been emergent. The nature of plate interactions that produced Ellesmerian deformation are unknown. The second phase began in the early Carboniferous, when plate movements of the Boreal Rifting Episode created the proto-Canada Basin by left-hand transform motion of a plate along the modern continental margin and the location of the Kaltag Fault of northern Alaska. As a marginal side effect of that motion, the Sverdrup Basin developed as a peri-cratonic incipient rift. From the Carboniferous to late Cretaceous the basin received about 13 km of cratonic-derived clastic detritus. From late Cretaceous to early Tertiary time, the Arctic Archipelago was disrupted by the interference of two plate movements originating in the Arctic and North Atlantic regions. Those events had three main effects: the craton was extended and a graben-filled depression formed in the southeastern part of the archipelago; the eastern and central parts of the Sverdrup Basin were compressed and uplifted (Eurekan Orogeny); and resultant elastics prograded northwestward toward the Canada Basin, to form the Arctic continental terrace wedge.

EXPLORATION PROSPECTS AND FUTURE PETROLEUM POTENTIAL OF THE CANADIAN ARCTIC ISLANDS

The offshore and onshore area of the Canadian Arctic Archipelago, 1.7 million sq km, is one of the most prospective frontier regions in Canada. The first onshore well was drilled at Winter Harbour in 1961, and the first offshore well was drilled from an ice‐strengthened island at Hecla in 1974. To date, more than 140 wells have been drilled, and 12.0 Tcf of recoverable gas have been discovered as well as a small amount of oil. The gas is largely Lower Jurassic, with smaller amounts in Triassic and Lower Cretaceous strata.The Canadian Arctic Archipelago is actually underlain by two prospective basins: the older Franklinian geosyncline, or basin, Cambrian through Devonian; and the younger Sverdrup successor basin, Late Mississippian through Middle Eocene. The principal orogenic events to affect the area were the Caledonian uplift (Devonian), the Ellesmerian orogeny, a compressive fold system was produced with décollement of the southern part of the Franklinian on the Ordovician Bay Fiord salt. Vertical uplift, with compression in the east, dominated the Eurekan orogeny.Objectives in the Franklinian basin include sub‐Bay Fiord (sub‐Ordovician) structures—mainly Lower Paleozoic carbonates and some terrigenous clastics; supra‐salt folds of the Parry Islands fold belt—Ordovician‐Devonian reefs and porous shelf carbonates; other Lower Paleozoic reef bodies; and porous Devonian clastics in the Parry Islands fold belt. Sverdrup basin objectives include mainly terrigenous clastic reservoirs in Pennsylvanian‐Cretaceous rocks, with structural (salt anticlines and diapirs; some folds in the east) and stratigraphic (pinchouts on the flanks of structures, and along the folds) possibilities. The greatest potential in the Sverdrup basin is in the central and western parts. Ultimate recovery of gas is estimated to be at least 125 Tcf.

Contributions to the tectonic history of the Innuitian Province, Arctic Canada

The Innuitian Tectonic Province contains the record of a Phanerozoic mobile belt in northern Greenland and the Canadian Arctic Archipelago. Two fundamentally different phases in its development were separated by the Devonian–Carboniferous Ellesmerian Orogeny. The first contribution focuses on the early Paleozoic history of a key area, the second summarizes the Carboniferous to Cenozoic history of most of the Canadian part of the province.(1) The early Paleozoic architecture of the mobile belt is apparent only in Ellesmere Island, where exposures extend from the Canadian Shield through Arctic Platform and Franklinian basin into the Pearya orogenic welt. The Franklinian basin comprised the deep but ensulic Hazen Trough and two unstable shelves bordering it on the northwest and southeast. The northwestern shelf was a site of felsic to intermediate volcanism, mainly in the Ordovician Period. Pearya, a site of granitic plutonism in the Devonian Period, supplied much of the clastic basin fill. Its core consisted of a metamorphic complex, about 1.0 Ga old, exposed in basement uplifts in nor thernmost Ellesmere Island. Both basin and welt essentially formed part of the North American Plate, although rifting, evident from mafic and ultramafic intrusions, probably occurred in Early Devonian (or latest Silurian) time. The history of this part of the province is tentatively interpreted as response to the opening and closure of an ocean, connected with lapetus, that separated northern Ellesmere Island and Greenland from the sialic crust of the present Lomonosov Ridge and Barents Shelf. The Lomonosov Ridge still seems to be attached to the shelf off northeasternmost Ellesmere Island.(2) Deep subsidence and filling of Sverdrup Basin dominated the Innuitian region from Early Carboniferous through Late Cretaceous time. Large halokinetic diapirs and mafic dikes and sills intruded axial parts of the basin succession through Mesozoic time. Steep faults along the northwestern margin of the basin are Middle Cretaceous and older. Part of the northwestern rim of Sverdrup Basin sagged in latest Cretaceous time, becomingpart of the Arctic continental terrace. In the Late Cretaceous and early Tertiary a system of large grabens developed through the southern part of the Innuitian region, linking Canada Basin with Baffin Bay; about the same time, uplift formed some large arches in the northeastern part of the region. Middle Eocene and older rocks were laterally compressed by a phase of pre-Miocene folding and faulting. Some uplift took place in Oligocene or Miocene time on Axel Heiberg Island. The distribution of recent earth quakes does not indicate the presence of modern active plate margins.

Cornwallis Fold Belt and the mechanism of basement uplift

Cornwallis Fold Belt is a north-trending anticlinorium more than 650 km (400 mi) long, that extends from the Precambrian Shield to the Sverdrup Basin. It is the folded and faulted sedimentary suprastructure that overlies Precambrian crystalline basement rocks of the Boothia Horst. The horst and fold belt represent lower and intermediate levels of the Boothia Uplift. Evolution of the Cornwallis Fold Belt includes two phases, formation and modification.Formation. The basic structure of the Cornwallis Belt, a relatively simple, steep-sided, north-plunging anticlinorium, was formed in the interval from Proterozoic to Late Devonian time during several discrete phases of deformation that involved a similar stress pattern. These phases can be attributed to pulses of differential vertical uplift of the underlying Boothia Horst. The earliest phases involved periods of gentle arching of the crystalline basement and sedimentary cover in late Proterozoic and early Paleozoic times. The fold belt was formed mainly by the Cornwallis Disturbance (new name) which involved further differential vertical uplift, and comprised several pulses: (1) Early Silurian, mild, affecting only part of the belt; (2) Early Devonian, very strong, affecting the entire belt; (3) late Early Devonian, moderately strong, affecting the entire belt; (4) Late Devonian, moderately strong, affecting the entire belt. Each pulse was a cycle that began with uplift and erosion of the fold belt and shedding of detritus into the adjacent basins, and was followed by broader regional subsidence and the resumption of deposition on the belt. Between pulses of uplift there was regional subsidence, during which the fold belt subsided less than the flanking basins and received less sediments.Differential vertical displacement originated in the crystalline basement, occurring along fault zones that define the Boothia Horst, and are parallel to and controlled by a steep to vertical north-trending foliation. Faults extend into the sedimentary suprastructure comprising the overlying Cornwallis Fold Belt, and change gradually upward from vertical faults to high-angle reverse faults, overturned anticlines, and finally to asymmetric anticlines. Because the fold belt plunges north, this gradational sequence occurs from south to north in the exposed part of the fold belt. Structures formed by early pulses were rejuvenated by later pulses with the same sense of movement.Modification. The basic structure of the Cornwallis Fold Belt was modified by other types of deformation during the interval from Late Devonian to the present. Many of the preexisting faults were reactivated, but with a different sense of movement. During the Late Devonian to Middle Pennsylvanian Ellesmerian Orogeny, southward overriding of upper levels of the sedimentary succession produced folds in the rocks east and west of the Cornwallis Fold Belt which had not been previously deformed and could easily be displaced southward on an underlying décollement surface. The north-trending Cornwallis Fold Belt, however, was an obstacle to southward overriding in which the effects of overriding were reduced. Zones of interference structures developed near the margins, guided by older basement-controlled structures. Left-lateral faults were developed on the western margin and right-lateral movement is probable on the eastern margin.The Cornwallis Fold Belt extends an unknown distance northward beneath the younger rocks of the Sverdrup Basin. These younger rocks were deposited during a long period of northward downwarping that began in mid-Mississippian time. This same downwarping caused an abrupt increase in the northward plunge of the fold belt.During the Cretaceous–Tertiary Eurekan Rifting Episode the Cornwallis Fold Belt was fragmented by block faulting. The horsts form islands, and the grabens form submarine channels, some of which contain thick sections of semiconsolidated Cretaceous–Tertiary sediments. Numerous other normal faults that occur within the fold belt probably formed at this time. Cretaceous–Tertiary faults within the Cornwallis Fold Belt have a rectilinear pattern that was inherited from preexisting structures.

Geology of Outstanding Arctic Aerial Photographs 3. Margin of Sverdrup Basin, Lyall River, Devon Island

ABSTRACT An outstanding aerial photograph of northern Grinnell Peninsula, Devon Island is reproduced with a geological interpretation. The area was occupied by three successive depositional basins: the Franklinian Miogeosyncline, the Arctic Platform and the Sverdrup Basin. Remnants of all three are preserved. The exposed section is more than 3300 m (11,000 ft) thick, including 12 Ordovician to Cretaceous map units and six unconformity surfaces. Three major deformations produced two intersecting structural trends. The Cornwallis Fold Belt developed first, with deformation ending in Late Devonian time. Its northerly trend was rejuvenated and influenced all younger structures. The Ellesmerian Orogeny occurred between Late Devonian and mid-Pennsylvanian time and included two phases. The first phase included a southward compression that put an east-west overprinting on northern parts of the Cornwallis Fold Belt. It apparently occurred before deposition of the Mississippian Emma Fiord Formation. This is a shaly and coaly transitional unit representing the earliest stages of the Sverdrup Basin. It apparently filled topographic lows in a fresh-water lake, as subsidence followed the first phase of folding. The second phase of the Ellesmerian Orogeny was contemporaneous with marked regional downwarping that developed the Sverdrup Basin. The phase was marked at Lyall River by folding and faulting near the zone of flexure. The topographic relief created provided coarse conglomerate to the contemporaneous Canyon Fiord Formation. A narrow east-trending, furrow-shaped high within the Sverdrup Basin was emergent through Canyon Fiord deposition. South of this high and largely cut off from the main basin was the narrow Lyall River Embayment of the Sverdrup Basin. The early history of the Sverdrup Basin was influenced greatly by pre-existing structure. The flexure that produced the basin caused an abrupt increase in the northward plunge of the Cornwallis Fold Belt. Numerous normal faults exposed in the area probably were active in the Cretaceous-Tertiary Eurekan Orogeny. They were controlled by older structures.

Geomagnetic variation anomalies in the Canadian arctic. I. Ellesmere Island and Lincoln Sea.

The geomagnetic variation anomaly on Ellesmere Island has been attributed to an elongated conductor located deep in the crust or in the upper mantle and striking northeast across the northern portion of the island. Recently observations have been made on the ice of the Lincoln Sea lying to the north of Ellesmere and Greenland, and the anomaly has been found to extend beyond the coast for a distance of 100km or more beneath the continental shelf. Fitting the data with a uniform current model suggests that the anomalous conductor is about 100km wide, 10km thick, and located in the crust at depths between 10 and 20km.The anomaly lies at the northeastern end of the Innuitian Province. It follows approximately the axis of the Franklinian Geosyncline (Ordovician to mid-Silurian) and parallels the structural trend of the lower paleozoic strata which were folded during the Ellesmerian Orogeny of Devonian-Mississippian times. There is no geophysical evidence suggesting a contemporary or recent origin for the anomaly. The high conductivity zone seems more likely to be caused by hydration and structural changes deep in the crust; the geological evidence suggests that it may be a relic of ancient tectonic activity.

Regional Geology of Northern Yukon1

ABSTRACT Structurally the northernmost Yukon is part of the Eastern Cordilleran System, and in many respects it is an eastward extension of Brooks Range and the adjacent structural provinces of northern Alaska. Comparisons may also be made between the geological history of the northern Alaska - northern Yukon region and that of the Canadian Arctic Islands, a fact that has led to some speculation concerning the possible contiguity of these two areas throughout much of Phanerozoic time. This report will deal with British and Barn Mountains, Old Crow Plain and Dave Lord Ridge. Richardson Mountains will not be discussed in detail. The Ordovician, Silurian and possibly much of the Cambrian are represented east of Dave Lord Ridge by approximately 10,000 ft of fine-grained clastic sediments, the Road River Formation. Rocks of similar age in British and Barn Mountains and Brooks Range are strongly deformed metasediments (Neruokpuk Formation). Deposition of the Road River Formation took place in a basin named the Richardson Trough, which may have been a southward extension of the Franklinian Geosyncline of the Canadian Arctic Islands. A major tectonic episode, the Ellesmerian Orogeny, affected northern Yukon, northern Alaska and the Arctic Islands in several separate phases during the Devonian. The Neruokpuk underwent low-grade regional metamorphism at this time and several granite stocks were emplaced, including that at Mount Sedgwick in British Mountains. Thick syntectonic and post-tectonic clastic wedges were formed nearly everywhere near the present Alaskan and Canadian Arctic coasts, except within the Yukon, as a result of a mid-Devonian pulse of the Ellesmerian Orogeny. Between the Early Mississippian and the Late Triassic the Lisburne Group and the Sadlerochit and Shublik formations were deposited. The Lisburne and Sadlerochit are two of the most important reservoir rocks at Prudhoe Bay. Lisburne sediments, mainly carbonates, are confined (within the report area) to British and Barn Mountains. The Sadlerochit Formation (coarse-grained, porous clastic deposits) is well developed in the Dave Lord Ridge area but is thin or absent in northeastern British Mountains. The Shublik is typically developed in British Mountains. The principal sediment source area for northern Alaska and northern Yukon during the Cambrian to Jurassic period appears to have been located off the 1 Manuscript received February 9, 1972. 2 Shell Canada, P.O. Box 880, Calgary, Alberta. Present address: Institute of Sedimentary and Petroleum Geology, Calgary. This paper has developed from a field and photogeological study carried out between July 1970 and March 1971 while the author was in the employ of J. C. Sproule and Associates Ltd. The project was carried out for Charter Oil Company Ltd. Both these companies are to be thanked for granting me permission to publish the material. C. W. Drew provided an invaluable preliminary photogeological interpretation of the project area. R. Cech was my very energetic field assistant. The ideas presented herein have benefited considerably from discussions with D. K. Norris, I. Tailleur and W. O. Kupsch, all of whom have read the manuscript. Finally, grateful thanks are due to Shell Canada Limited for providing me with drafting and typing services. L. H. Taylor drew the illustrations and Mrs. J. Barnes typed the final manuscript. End_Page 81------------------------- present Arctic Coast and may have been part of the same source area that contributed detritus to the Canadian Arctic Islands region. Jurassic, Cretaceous and Tertiary sediments are almost exclusively clastic in northern Yukon. They were derived from several sources including an ancestral Brooks Range and Campbell Uplift of the Inuvik area. The Cretaceous marks a major shift in sediment dispersal patterns, particularly in northern Alaska, as a result of large-scale changes in the distribution of land and water masses at this time. These may have been caused by major continental-drift movements in the area of the Arctic Ocean Basin. A major tectonic episode, the Eurekan Orogeny, took place between Middle Cretaceous and Early Tertiary times in northern Yukon (and in Alaska and the Arctic Islands), involving all but the most recent sediments. No igneous activity has been recorded in connection with the Eurekan Orogeny in northern Yukon but most of the structural deformation of the post-Devonian rocks dates from this time.

Upper Devonian Stratigraphy and Structure, Western Canadian Arctic Islands: ABSTRACT

Upper Devonian strata (Melville Island Group) in the western Arctic Islands are part of a clastic wedge at least 10,000 ft thick. The strata represent the uppermost part of the Lower to Middle Paleozoic sequence of the Franklinian miogeosyncline. Three major depositional facies are recognized. (1) Marine shelf facies--interbedded green, very fine-grained, argillaceous quartz sandstone, siltstone, and shale with a few marine fossils. Organic limestones are rare. (2) High energy shoreline facies--white, fine to coarse-grained, well-sorted quartz sandstone with plant and fish remains. (3) Low energy shoreline facies--interbedded, very fine-grained, argillaceous quartz sandstone, siltstone, shale, and coal. On Bathurst and Melville Islands, the Group is divided into the Hecla Bay Formation (early to middle Frasnian) consisting mainly of high-energy shoreline facies, and the overlying Griper Bay Formation consisting of 2 informal members. The lower member (mid to late Frasnian) consists of marine shelf facies, and the upper member (early to middle Famennian) consists of high- and low-energy shoreline facies. On Prince Patrick and Banks Islands only the Griper Bay Formation is developed. Two informal members are recognized, the lower comprising the entire Frasnian stage, and the upper a part of the Famennian. The source area for the sediments is interpreted to have been a tectonic highland situated along the present western continental margin. Mississippian (Ellesmerian) deformation resulted in the development of open anticline-syncline couples and normal faults. On Bathurst and Melville Islands these structures trend east-west. In contrast, the structures trend north-south on Banks Island. This sharp bend in the Ellesmerian fold belt may be interpreted to be an orocline superimposed on the Franklinian geosyncline during the Ellesmerian orogeny. Restoration of the orocline clarifies otherwise irreconcilable facies relations in the Upper Devonian strata of the Western Arctic Islands. End_of_Article - Last_Page 2491------------