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Title: Brookian maturation and erosion framework of North Alaska

Abstract

Quantifying the timing and magnitude of syn- and post-orogenic loading and unroofing within fold and thrust deformation belts and adjacent foreland basins is critical for evaluating reservoir quality, the timing and degree of source rock maturation, and the timing of trap development. The present-day sub-surface thermal structure and the timing and amount of eroded section during the Brookian Orogeny in North Alaska have been quantified by integrating DST and log temperature, apatite fission track, vitrinite reflectance, and sonic velocity data. Constraining the present-day thermal structure is particularly important for interpretation of thermal indicator data in this area, because thermal gradients systematically vary within the range 25-55 {degree}C/km with the highest gradients present along the crest of the Barrow Arch. Erosion estimates range from 0-0.6 km in the Prudhoe Bay/East Beaufort Sea area, and increase to the west and south, reaching {approximately}1.8 km in the Point Barrow area, and >3.7 km along the Brooks Range mountain front. The spatial and temporal distribution of erosion reflects contributions form short-term compressional and long-term isostatic processes. Significant erosion (>2-3 km) during short periods (<5 Ma) is localized along thrust sheets in-board of the deformational fonts and was responsible for synchronous deposition of clastic wedgesmore » outboard of the deformational fronts. Surface fission track data delineate the culmination of several discrete Brookian thrust belts (ca. 60, 45, 20 Ma), the latter two of which are localized in the NE Brooks Range. Protracted post-orogenic erosion west of the Shaviovik Fron since 60 Ma is due to flexural tilting of the foreland and represents an isostatic response to unroofing of the orogen.« less

Authors:
 [1]; ;  [2]
  1. Arco Alaska, Inc., Anchorage, AK (United States)
  2. Arco EPT, Plano, TX (United States)
Publication Date:
OSTI Identifier:
425509
Report Number(s):
CONF-960527-
TRN: 96:004994-0142
Resource Type:
Conference
Resource Relation:
Conference: Annual convention of the American Association of Petroleum Geologists, Inc. and the Society for Sedimentary Geology: global exploration and geotechnology, San Diego, CA (United States), 19-22 May 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 AAPG annual convention. Volume 5; PB: 231 p.
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; ALASKAN NORTH SLOPE; TECTONICS; EROSION; SOURCE ROCKS; MATURATION; GEOLOGIC TRAPS

Citation Formats

Decker, J., Corrigan, J., and Bergman, S. Brookian maturation and erosion framework of North Alaska. United States: N. p., 1996. Web.
Decker, J., Corrigan, J., & Bergman, S. Brookian maturation and erosion framework of North Alaska. United States.
Decker, J., Corrigan, J., and Bergman, S. 1996. "Brookian maturation and erosion framework of North Alaska". United States. doi:.
@article{osti_425509,
title = {Brookian maturation and erosion framework of North Alaska},
author = {Decker, J. and Corrigan, J. and Bergman, S.},
abstractNote = {Quantifying the timing and magnitude of syn- and post-orogenic loading and unroofing within fold and thrust deformation belts and adjacent foreland basins is critical for evaluating reservoir quality, the timing and degree of source rock maturation, and the timing of trap development. The present-day sub-surface thermal structure and the timing and amount of eroded section during the Brookian Orogeny in North Alaska have been quantified by integrating DST and log temperature, apatite fission track, vitrinite reflectance, and sonic velocity data. Constraining the present-day thermal structure is particularly important for interpretation of thermal indicator data in this area, because thermal gradients systematically vary within the range 25-55 {degree}C/km with the highest gradients present along the crest of the Barrow Arch. Erosion estimates range from 0-0.6 km in the Prudhoe Bay/East Beaufort Sea area, and increase to the west and south, reaching {approximately}1.8 km in the Point Barrow area, and >3.7 km along the Brooks Range mountain front. The spatial and temporal distribution of erosion reflects contributions form short-term compressional and long-term isostatic processes. Significant erosion (>2-3 km) during short periods (<5 Ma) is localized along thrust sheets in-board of the deformational fonts and was responsible for synchronous deposition of clastic wedges outboard of the deformational fronts. Surface fission track data delineate the culmination of several discrete Brookian thrust belts (ca. 60, 45, 20 Ma), the latter two of which are localized in the NE Brooks Range. Protracted post-orogenic erosion west of the Shaviovik Fron since 60 Ma is due to flexural tilting of the foreland and represents an isostatic response to unroofing of the orogen.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1996,
month =
}

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  • Quantifying the timing and magnitude of syn- and post-orogenic loading and unroofing within fold and thrust deformation belts and adjacent foreland basins is critical for evaluating reservoir quality, the timing and degree of source rock maturation, and the timing of trap development. The present-day sub-surface thermal structure and the timing and amount of eroded section during the Brookian Orogeny in North Alaska have been quantified by integrating DST and log temperature, apatite fission track, vitrinite reflectance, and sonic velocity data. Constraining the present-day thermal structure is particularly important for interpretation of thermal indicator data in this area, because thermal gradientsmore » systematically vary within the range 25-55 [degree]C/km with the highest gradients present along the crest of the Barrow Arch. Erosion estimates range from 0-0.6 km in the Prudhoe Bay/East Beaufort Sea area, and increase to the west and south, reaching [approximately]1.8 km in the Point Barrow area, and >3.7 km along the Brooks Range mountain front. The spatial and temporal distribution of erosion reflects contributions form short-term compressional and long-term isostatic processes. Significant erosion (>2-3 km) during short periods (<5 Ma) is localized along thrust sheets in-board of the deformational fonts and was responsible for synchronous deposition of clastic wedges outboard of the deformational fronts. Surface fission track data delineate the culmination of several discrete Brookian thrust belts (ca. 60, 45, 20 Ma), the latter two of which are localized in the NE Brooks Range. Protracted post-orogenic erosion west of the Shaviovik Fron since 60 Ma is due to flexural tilting of the foreland and represents an isostatic response to unroofing of the orogen.« less
  • Throughout Cretaceous and Tertiary time on the North Slope, clastic debris was shed northward from the rising ancestral Brooks Range to fill the adjacent foredeep and to prograde northeasterly across the subsiding Barrow arch to form a passive margin sequence. Study of these southern source sedimentary rocks, known as the Brookian sequence, in wells and on seismic records along the Barrow arch in the National Petroleum Reserve in Alaska (NPRA) and only in wells east of NPRA shows a consistent style of deposition. This style is characterized on seismic reflection records by a distinct topset-foreset-bottomset profile that is inferred tomore » represent a time line and thus a depositional profile.« less
  • The nomenclature of the structural elements of Alaska, particularly North Slope. Alaska is discussed in an effort to standardize the names for these geologic structures. The author proposes that the name Colville basin be used instead of Colville geosyncline or Colville trough or Colville foredeep. He also recommends that Barrow inflection by substituted for Barrow Arch.
  • The Brookian orogenic belt (Seaward Peninsula, Brooks Range, Ruby geoanticline) forms three sides of the Cretaceous Yukon-Koyukuk basin of west-central Alaska. Low Sr/sub j/ values from igneous rocks within the basin suggest that it is not underlain by older continental crust. The basin encloses a south-facing horseshoe-shaped trend of Lower Cretaceous andesitic volcanic rocks. Major-element chemistry of these rocks indicates that they are calc-alkaline and of island-arc affinity. Berriasian to Valanginian volcanic rocks in the basin are predominantly clastic and were deposited in shallow marine to subaerial environments. Marked subsidence began during Hauterivian time, accompanied by a change to highlymore » potassic (shoshonitic) pyroclastic volcanism. During the Barremian (Aptian.), these tuffs were interbedded with Brookain-derived tubidites, deposited in a trough between the subsided volcanic platform and the uplifted Brookian metamorphic belt. Paleoflow was clockwise around the basin from west to east. By the Albian, significant volcanism had ceased, and the intervening trough filled with Brookian sediment. The Brookian orogency apparently resulted from attempted subduction of the North American margin beneath the intraoceanic Koyukuk arc. The relatively long timespan (approximately 30 Ma) between initial continental underthrusting (Tithonian.) in the Brooks Range and the shutoff of arc volcanism (Aptian.) suggests a very slow convergence rate (1-2 cm/year).« less
  • The Brookian orogenic belt (Seaward Peninsula, Brooks Range, Ruby geoanticline) forms three sides of the Cretaceous Yukon-Koyukuk basin of west-central Alaska. Low Sr/sub j/ values from igneous rocks within the basin suggest that it is not underlain by older continental crust. The basin encloses a south-facing horseshoe-shaped trend of Lower Cretaceous andesitic volcanic rocks. Major-element chemistry of these rocks indicates that they are calc-alkaline and of island-arc affinity. Berriasian to Valanginian volcanic rocks in the basin are predominantly clastic and were deposited in shallow marine to subaerial environments. Marked subsidence began during Hauterivian time, accompanied by a change to highlymore » potassic (shoshonitic) pyroclastic volcanism. During the Barremian (Aptian.), these tuffs were interbedded with Brookian-derived tubidites, deposited in a trough between the subsided volcanic platform and the uplifted Brookian metamorphic belt. Paleoflow was clockwise around the basin from west to east. By the Albian, significant volcanism had ceased, and the intervening trough filled with Brookian sediment. The Brookian orogency apparently resulted from attempted subduction of the North American margin beneath the intraoceanic Koyukuk arc. The relatively long timespan (approximately 30 Ma) between initial continental underthrusting (Tithonian.) in the Brooks Range and the shutoff of arc volcanism (Aptian.) suggests a very slow convergence rate (1-2 cm/year).« less