North Chukchi Basin Research Articles

Cenozoic Clinoform Complexes and the Geological History of the North Chukchi Basin (Chuckchi Sea, Arctic)

A new seismostratigraphic model was developed for the sedimentary cover of the North-Chukchi Basin and the main paleogeographic events that occurred within this territory were interpreted. The post-rift sedimentary history of the North-Chukchi basin can be divided into three stages: the late Cretaceous–Paleocene with strong progradation of shelf sedimentary packages to the north, the middle Eocene–Miocene with gradual differently oriented filling of the basin from different sides, and the late Miocene until the present. At the last stage, the shelf outlines were formed along with slow aggradation of the clinoform complex with an insignificant northern deviation.

Cenozoic clinoform complexes and geological history of the North-Chukchi basin (Chukchi sea, Arctic)

New sesmostratigraphic model has been established for the sedimentary cover of the North-Chukchi basin. Based on the model interpretation of the main paleogeographic events within the territory was performed. We identify three stage in the post-rift sedimentary history of the North-Chukchi basin: Late Cretacerous to Paleocene stage when strong progradation of shelf sedimentary packages was occurred, Mid Eocene — Miocene, with gradual infilling of the basin from different sides and Late Miocene to Present stage with present shapes of the shelf and slow clinoform complex aggradation.

Meso–Cenozoic evolution of the southwestern Chukchi Borderland, Arctic Ocean

Abstract A regional stratigraphic framework is developed for the North Chukchi Basin and southern margin of the Chukchi Borderland based on a grid of 2D multi-channel seismic reflection profiles tied to exploration wells on the U.S. Chukchi Shelf. The northern flank of the North Chukchi Basin displays a 16 km succession of mainly Cretaceous and Cenozoic strata that progressively onlaps an unconformity (Au) on the southern margin of the Borderland. Rocks beneath the unconformity are inferred to represent (A) crystalline basement that may have affinity to the Peary terrane, (B) deformed growth strata that may be related to Carboniferous to Jurassic strata on the Chukchi Shelf, and (C) seaward dipping reflections (SDRs) likely related to oceanic igneous rocks or exhumed mantle beneath the North Chukchi Basin. The SDRs indicate that the southwestern margin of the Borderland is a rifted continental margin and loosely constrained age control suggests that rifting occurred between Middle Jurassic and earliest Cretaceous. Cretaceous through Cenozoic strata that fill the North Chukchi Basin are part of the Brookian megasequence deposited across the foreland of the Chukotka and Brooks Range orogens. These strata form a series of clinothems deposited by northward-migrating depositional systems that progressively filled the North Chukchi Basin and buried the southern flank of the Borderland. Onlap of the Au by bottomset facies indicates that deep water conditions prevailed along the northern basin margin during Aptian–Oligocene. Foreset and topset facies onlap and overtop the highest standing part of the Borderland and indicate that marine slope and shallow marine to deltaic environments reached the Borderland during the Oligocene and persisted thereafter.

Crustal architecture of the East Siberian Arctic Shelf and adjacent Arctic Ocean constrained by seismic data and gravity modeling results

The Eastern Siberian Arctic Shelf (ESAS) represents a geologically complex realm with a tectonic history that is related to the final stages of the formation of the Pangaea supercontinent during the Mesozoic and its subsequent disintegration during the Late Cretaceous and Cenozoic. It is a key region to constrain the origin of the deep-water basins and intervening ridges of the Amerasia Basin. We present results of gravity modeling of published seismic refraction and reflection profiles acquired between 1989 and 2012 over the ESAS and adjacent Arctic Ocean along five composite geotransects using Getech’s satellite altimeter-derived gravity data. Our main goal was to examine published crustal models and to present new models for the ESAS that are constrained by both seismic data and 2D gravity forward modeling. We consider several topics important for understanding Arctic geology: (i) hyperextension within the Laptev Rift System and the possible extent of the exhumed mantle, (ii) the relationship between the New Siberian Shelf and the Lomonosov Ridge, (iii) the nature of the collapsed upper Mesozoic fold belt in the southern part of the East Siberian Sea, (iv) the character of transition between the De Long Massif and the deep-water Podvodnikov Basin, (v) the lateral extent of the hyperextended North Chukchi Basin and the nature of its basement, and (vi) relationship between the Mendeleev Ridge and Chukchi Plateau crustal domains. Our results do not confirm the previously inferred extent of continental crust beneath the oceanic realm. The latter is dominated by High Arctic Large Igneous Province (HALIP) igneous crust. We discuss the existence of a dismembered continental Bennett-Barrovia block that is currently represented by three smaller fragments/massifs. When restored to its possible single state, this block can play a crucial role in reconstructing the pre-Canada Basin Arctic.

Present-day structure and stages of tectonic evolution of Wrangel Island, Russian eastern Arctic Region

Present-day structure of Wrangel Island was formed during two main stages of Mesozoic-Cenozoic deformation. The general fold-thrust structural grain of the island, characterized by northern vergence and complicated by NW-trending right-lateral strike-slip faults, originated in the post-Triassic. Mesostructural data indicate a near-meridional orientation of regional compression. This deformation stage was related to the orogeny in the New Siberian-Chukchi Fold System, which occurred at the end of Neocomian in the pre-Aptian. The next stage was characterized by a near-meridional and NNW-SSE extension established by superposition of normal, right-lateral strike-slip, and pull-apart kinematics upon the former fold-thrust structure. Comparison of the structural and the published seismic data allows us to suggest the later stage of compression to be in the Late Cretacous-Paleocene, which is correlated to the Mid-Brookian angular unconformity in Arctic Alaska and North Chukchi Basin. Accordingly, the Cenozoic age (since Paleocene-Eocene) of the main extension and right-lateral transtension most likely corresponds to opening of the South Chukchi (Hope) Basin localized immediately to the south of the Wrangel-Herald Arch (High). The difference in structural patterns of the Silurian-Lower Devonian and the Upper Devonian (?)-Triassic rocks is evidence for deformation related to the Ellesmerian Orogeny in the Middle-Late Devonian.

The evolution of the Akademicheskaya structure in the North Chukchi basin and its relationship with the evolution of the Wrangel-Herald thrust zone

The structure and the principal evolution stages of the Akademicheskaya consedimentary structure in the North Chukchi sedimentary basin are discussed. The formation of the discussed structure took place under the effects of compressional strain from the Wrangel-Herald fold-thrust zone. This took two stages: Late Cimmerian, which contributed the most to the formation of the structure and was manifested most intensively in the first half of the Late Cretaceous, and a less intensive stage that probably occurred in the Miocene.

Chapter 33 Stratigraphic and tectonic framework of the US Chukchi Shelf: exploration insights from a new regional deep-seismic reflection survey

Abstract The US Chukchi Shelf is a proven petroleum province similar to the prolific hydrocarbon-bearing region in the adjacent North Slope of Alaska. This shelf is part of the Arctic Alaska plate that was presumably connected to the Canadian Arctic Islands until the opening of the Canada Basin. A new data set (3130 km) of deep 2D seismic reflection profiles, acquired in 2006 and depth processed to 40 km, provides excellent images of the drillable ( c . 8 km depth) stratigraphy as well as of deeper structures. The data also permit regional mapping of the tops of crystalline basement and the Moho discontinuity. The area has a tectonic history of multiple phases of rifting: a pre-Late Devonian phase that culminated in inversion and thrusting; a Late Devonian–Mississippian phase that accommodated Ellesmerian sedimentary deposits as a sag sequence; and a Jurassic to Early Cretaceous phase that is contemporaneous with the opening of the Canada Basin. Hanna Trough is recognized as a Palaeozoic basin with a multistage history while the North Chukchi Basin formed in early Cretaceous as an extensional basin. Only five wells have been drilled in the area; hence numerous opportunities for further exploration exist in the Chukchi Shelf.

The superdeep North Chukchi Basin: formation by eclogitization of continental lower crust, with petroleum potential implications

The large North Chukchi Basin in the northeastern Eurasian shelf is filled with up to 22 km of sediments, which is far thicker than filling a basin upon oceanic crust would require. The basin sedimentation began 380 Myr ago, and about 16 km of sediments have been deposited for the past 125 Myr, long after the oceanic crust would have completed its subsidence. This fact is in favor of the continental instead of oceanic crust origin. Rapid basin subsidence appears to be driven by a mechanism other than crustal stretching as the latter has no evidence over the greatest part of the basin area. The suggested basin formation model implies a transformation of gabbro into denser eclogite in the lower crust and related contraction of mafic rocks. To sustain consolidated crust beneath 22 km thick sediments, the layer of dense eclogites under the granitic layer must be at least ∼25 km thick. The presence of basement flexures formed at several stages of the basin evolution indicates a considerable loss of lithospheric rigidity under the effect of fluid infiltration from small mantle plumes. The fluids catalyzed the eclogitization and thus increased the subsidence rate. Rapid subsidence apparently occurred in Barremian-Albian time when the basin had accumulated up to 11.5 km of sediments. Besides the Early Cretaceous event, there were, possibly several older events of rapid subsidence. This basin subsidence history, along with the evidence of steep lithospheric flexure, is a known feature of large petroleum basins. Therefore, the North Chukchi Basin may be expected to be an oil and gas producer.

Multiple-Stage Deformation along the Southern Flank of the North Chukchi High, Chukchi Sea, Alaska: ABSTRACT

Structural and stratigraphic relations along the southern edge of the North Chukchi high provide insights into the timing and mechanics of Late Cretaceous and Cenozoic tectonic events in the northern Chukchi Sea. In this area, the easternmost strand of the north-trending Hanna wrench fault zone is deflected to the northeast and terminates in a series of reverse faults along the southern edge of the high. Areas east of the Hanna fault zone were characterized by tectonic stability during this period of time. Within the fault zone, east-west-trending box folds and reverse faults accompanied uplift of the North Chukchi high and erosion of the entire Ellesmerian sequence along its southern margin. Stratigraphic and structural relations indicate that this compressional deformation began during the Early Cretaceous (Albian ) but ceased prior to the Late( ) Cretaceous. During the early Cenozoic( ), the northern part of the Hanna fault zone was reactivated as an extensional systems which controlled the development of a local basin. Some faults which showed an early history of reverse displacement were reactivated as normal faults during this late-stage tectonic event. This data is consistent with a model for Early Cretaceous impingement of adjacent blocks at a constrained corner nearmore » the North Chukchi high during the rift opening of the North Chukchi basin. The compressional deformation ceased prior to the Cenozoic when the opposing blocks in the constrained corner finally escaped past each other. Continued rifting and subsidence of the North Chukchi basin resulted in late-stage extensional overprinting of earlier compressional structures.« less

Implications of Offshore Northern Alaska Geology for Origin of Canada Basin, Arctic Ocean: ABSTRACT

Geologic mapping and petroleum exploration in northern Alaska and seismic surveys offshore suggest that 2 pulses of rifting created the Canada basin. Mississippian to Triassic miogeoclinal rocks in northern Alaska, derived from a now-displaced northerly source land, correlate with similar strata in the Canadian Arctic Islands. Underlying Ordovician and Silurian argillite and graywacke may correlate with the clastic succession in Heezen trough of the Arctic Islands. Closing Canada basin about a Mackenzie delta pole would rejoin these correlative rocks and recreate a unified pre-Jurassic Arctic paleogeography. Rifting began in earliest Jurassic time, creating a west-northwest-trending trough beneath the Beaufort Shelf and probably the southern Canada basin. The main rifting pulse, however, began in late Neocomian time, and the main post-rift progradational sedimentary prism off Alaska is Aptian or Albian and younger. Apparently both late Neocomian and Laramide rifting thinned the crust beneath North Chukchi basin. Marked basinward thickening of Cretaceous strata records the earlier event, and extensional faulting and basinward thickening of Tertiary strata record the later one. The high-standing, north-trending ridges and troughs of the Chukchi borderland, which trend into the North Chukchi basin from the north, may represent localized Laramide(?) crustal extension subparallel to that which created the Laramide(?) and Cenozoic Makarov and Eurasia basins of the Arctic Ocean. This model requires crustal shortening between the Chukchi borderland and Canada basin and transform faults north and south of the borderland. North of our seismic lines, the southern transform may be buried by Tertiary sediment of the North Chukchi basin. End_of_Article - Last_Page 259------------

Geologic Framework and Petroleum Potential of United States Chukchi Shelf North of Point Hope, Alaska: ABSTRACT

A reconnaissance grid of 24-channel seismic-reflection data indicates that most of the United States Chukchi shelf north of Point Hope, Alaska, is prospective for petroleum. The prospective rocks, which consist of four stratigraphic sequences, rest on the Arctic platform, a regional erosional surface cut across mildly metamorphosed lower Paleozoic rocks in Late Devonian time. The Eo-Ellesmerian sequence, interpreted to contain mainly Mississippian nonmarine deposits, is 5+ km (16,500 ft) thick and fills local sags and faulted depressions in the Arctic platform. Mississippian to Neocomian stable shelf clastic and carbonate beds of the Ellesmerian sequence, 0 to 7.7+ km (25,000 ft) thick, underlie most of the shelf but are absent from Barrow arch and the outer shelf of the ortheastern Chukchi Sea. Albian and Upper Cretaceous intradelta and prodelta deposits of the lower Brookian sequence, which thicken from 250 m (800 ft) on Barrow arch to 7.5+ km (24,500 ft) to the southwest, northwest, and north, underlie most of the shelf. The upper Brookian sequence, inferred to consist of marine and nonmarine clastic deposits of mainly or entirely Tertiary age, is 0 to 5.6+ km (18,500 ft) thick. It occurs only in Nuwuk and North Chukchi basins and locally as canyon fill beneath the central Chuckchi shelf. The northern Chukchi shelf contains seven provinces of contrasting tectonic origin and structural style. Nuwuk basin, a progradational clastic prism containing 12+ km (39,500 ft) of lower and upper Brookian strata and numerous growth faults, overlies a rifted margin of Neocomian age beneath the outer shelf and slope of the northeastern Chukchi Sea. North Chukchi basin, which underlies the outer shelf west of Nuwuk basin, contains Ellesmerian beds and 12+ km (39,500 ft) of lower and upper Brookian strata. It may also overlie a Neocomian rifted margin, but was deepened by Laramide extensional rifting. South of these basins, shelf structure is controlled by the geometry of the Arctic platform, which slopes gently southwest from a depth of 0.25 km (800 ft) on Barrow arch to about 13 km (4 ,650 ft) off Point Lay. In the central part of the shelf, the platform is somewhat faulted and folded and descends to a depth of 10+ km (33,000 ft) to form the north-trending Hanna trough. West of the trough the platform rises to within 1 km (3,300 ft) of the seabed and is broken by numerous normal faults. The southern part of the platform contains a thick lower Brookian section with numerous northwest-striking, northeast-verging detachment folds. The fold province is bounded on the southwest, off Cape Lisburne, by the northwest-striking Herald arch overthrust belt at which one or more southwestward-dipping thrusts brought Ellesmerian and older strata to the seabed. The seismic and extrapolated onshore data suggest that Nuwuk and North Chukchi basins, Hanna trough, and the Arctic platform east and west of the trough could contain significant deposits of oil or gas. The potential of the fold belt, however, is modest, and of Herald arch slight. Small areas on Barrow arch and the Arctic platform west of Hanna trough lack potential because they are underlain by less than 1 km (3,300 ft) of prospective section. End_of_Article - Last_Page 474------------

Acoustic properties of northern Alaska shelves in relation to the regional geology

More than 100 airgun‐sonobuoy records from the northern Alaska shelves have been reduced to yield an average of six layers from each record. Seafloor sound velocities, regional velocity functions, and high‐resolution velocity‐depth inversions were computed. Low seafloor velocities in the northwest part of the otherwise Cretaceous seafloor of the Colville foredeep represent thin Tertiary sediments that overstep the Barrow arch from the north. Anticlinal cores of ‘mid‐shelf arches’ (Grantz et al., 1981) appear as 200‐m/s velocity increases in the Neogene seafloor of the western Beaufort shelf. Very recent or currently, active sedimentation in the central Hope basin is indicated by low seafloor sound velocities. The value of K in the least squares determination of V = V0 + Kt (t is one‐way vertical travel time) decreases toward the east from 1.74 km/s2 just east of Point Barrow of 1.67 km/s2 around Prudhoe Bay, to 1.53 km/s2 near the Mackenzie River. This decrease in K corresponds with an eastward increase in the thickness of the clastic rocks within the youngest part of the Brookian sequence (Early Cretaceous to Quaternary). A 2.1‐km/s2 value of K is the Brookian sequence of the north Chukchi basin suggests a change in the relative proportions of Cretaceous and Tertiary sediments between the basin and the Beaufort shelf. High‐resolution velocity‐depth inversions, using closely digitized travel time data, yield velocities at about 40‐m vertical spacings. Calculated values of near‐surface velocity gradients determined by velocity‐depth plots of these data are generally not in good agreement with the values predicted from the velocity functions, which are statistical generalizations based on conventional refraction picks that resolve layers no thinner than about 250 m. The discrepancies are minimized by use of independently determined seafloor velocities.

Implications of Geologic Structure and Regional Sedimentation Patterns for Rifting Geometry of Arctic Basin: ABSTRACT

The smooth, passive continental margin north of Alaska is geometrically more complex than its simple physiography suggests. Multichannel seismic reflection profiles across the continental shelf reveal three sectors of contrasting structure and stratigraphy. The Barrow sector of central northern Alaska is characterized by a prominent arch in lower Paleozoic metasedimentary basement rocks overlain by a southward-thickening wedge of Mississippian to Lower Cretaceous (Neocomian) shelf sediments and a northward-thickening prism of Lower Cretaceous (Albian) to Tertiary clastic sediments. The Chukchi and Barter Island sectors, lying respectively west and east of the Barrow sector, comprise Mesozoic and Tertiary basins so deep that acoustic basement was not reached. We suggest th t this geometry (in which lower Paleozoic basement rocks extend much farther north in the central sector than they do in the east and west) is inherited from the configuration of the rift that opened the Arctic basin, probably beginning in Early Jurassic time. In this scheme, old, pre-rift highlands, originally continuous with the basement rocks of the central Barrow sector, were rotated northward away from Alaska along two sectors of the rift that lay well south of the present-day shelf edge. In these, the Chukchi and Barter Island sectors, the rift created room for the deep shelf basins observed there now. In the intervening Barrow sector, the rift opened along the present-day shelf edge, leaving a broad tongue of lower Paleozoic rocks, the site of upper Paleozoic and lower Mesozoic hi hlands, attached to Alaska. Presumably the sector boundaries were ridge-ridge transform faults during nascent rifting. The Chukchi-Barrow sector boundary is well defined by the trend of the Northwind Escarpment and the abrupt termination of the Barrow arch against the North Chukchi basin. The Barrow-Barter Island boundary is more obscure and is inferred from the provenance and distribution of Mesozoic sediments in northeastern Alaska and Yukon Territory. End_of_Article - Last_Page 714------------

Geology and tectonic development of the continental margin north of Alaska

The continental margin north of Alaska, as interpreted from seismic reflection profiles, is of the Atlantic type and consists of three sectors of contrasting structure and stratigraphy. The Chukchi sector, on the west, is characterized by the deep late Mesozoic and Tertiary North Chukchi basin and the Chukchi Continental Borderland. The Barrow sector of central northern Alaska is characterized by the Barrow arch and a moderately thick continental terrace build of Albian to Tertiary clastic sediment. The terrace sedimentary prism is underlain by lower Paleozoic metasedimentary rocks. The Barter Island sector of northeastern Alaska and Yukon Territory is inferred to contain a very thick prism of Jurassic, Cretaceous and Tertiary marine and nonmarine clastic sediment. Its structure is dominated by a local deep Tertiary depocenter and two regional structural arches. We postulate that the distinguishing characteristics of the three sectors are inherited from the configuration of the rift that separated arctic Alaska from the Canadian Arctic Archipelago relative to old pre-rift highlands, which were clastic sediment sources. Where the rift lay relatively close to northern Alaska, in the Chukchi and Barter Island sectors, and locally separated Alaska from the old source terranes, thick late Mesozoic and Tertiary sedimentary prisms extend farther south beneath the continental shelf than in the intervening Barrow sector. The boundary between the Chukchi and Barrow sectors is relatively well defined by geophysical data, but the boundary between the Barrow and Barter Island sectors can only be inferred from the distribution and thickness of Jurassic and Cretaceous sedimentary rocks. These boundaries may be extensions of oceanic fracture zones related to the rifting that is postulated to have opened the Canada Basin, probably beginning during the Early Jurassic.