Geology of northern Alaska

Moore, Thomas E.; Wallace, Wesley K.; Bird, Kenneth J.; Karl, Susan M.; Mull, Charles G.; Dillon, John T.

doi:10.1130/dnag-gna-g1.49

Cited by 188 publications

(309 citation statements)

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“…Examples of such deposits include: the Kuna and Tupik formations and the Akmalik and Imnaitchiak forma- (Jin et al, 1997;Menning, 1995), major sequence-bounding unconformities and formations in proximal basin margin areas and correlative units in distal basin centre areas, assumed (Golonka et al, 1994) and measured (Ogg and Steiner, 1991) palaeolatitudes in ‡N, on-land climatic setting based on non-marine indicators (Beauchamp, 1994) and palynomorphs , and assumed marine temperatures based on biogenic and abiogenic indicators (Beauchamp and Desrochers, 1997). Modi¢ed from and Beauchamp et al (2001). tions of northern Alaska (Moore et al, 1994;, the Hart River and Blackie formations of the northern Yukon Territory (Richards et al, 1997;, the Ban¡ and the Prophet formations from the southwest regions of the Northwest Territories to southwestern Alberta , the Lodgepole and Middle Canyon formations and the Wilson Creek Member of the Wood River Formation of the northwestern United States (Pole and Sandberg, 1991;Reid and Dorobek, 1991;Mahoney et al, 1991).…”

Section: Prior To Pce: Sakmarian and Earliermentioning

confidence: 99%

“…missing Detterman et al, 1975;Dutro and Silberling, 1988;Crowder, 1990;Moore et al, 1994; Thorsteinsson, 1974;Nassichuk and Wilde, 1977;Beauchamp, 1993Beauchamp, , 1994Beauchamp and Henderson, 1994;Beauchamp and Desrochers, 1997 8. Sverdrup Basin, northern margin chloroforam, Nansen, Raanes bryonoderm, Great Bear Cape bryonoderm, Degerbols bryonoderm hyalosponge, unnamed unit Thorsteinsson, 1974;Davies and Nassichuk, 1991;Beauchamp, 1993Beauchamp, , 1994Beauchamp et al, 1995a,b;Beauchamp and Henderson, 1994;Beauchamp and Desrochers, 1997 9.…”

Section: Expansion Of Pce: Guadalupianmentioning

confidence: 99%

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Growth and demise of Permian biogenic chert along northwest Pangea: evidence for end-Permian collapse of thermohaline circulation

Beauchamp

Baud

2002

Palaeogeography, Palaeoclimatology, Palaeoecology

272

132

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The Permian Chert Event (PCE) was a 30 Ma long episode of unusual chert accumulation along the northwest margin of Pangea, and possibly worldwide. The onset of the PCE occurred at about the Sakmarian^Artinskian boundary in the Sverdrup Basin, Canadian Arctic, where it coincides with a maximum flooding event, the ending of high-frequency/high-amplitude shelf cyclicity, the onset of massive biogenic chert deposition in deep-water distal areas, and a long-term shift from warm-to cool-water carbonate sedimentation in shallow-water proximal areas. A similar and coeval shift is observed from the Barents Sea to the northwestern USA. A landward and southward expansion of silica factories occurred during the Middle and Late Permian at which time warm-water carbonate producers disappeared completely from the northwest margin of Pangea. Biotically impoverished and increasingly narrow cold-water carbonate factories (characterised by non-cemented bioclasts of sponges, bryozoans, echinoderms and brachiopods) were then progressively replaced by silica factories. By Late Permian time, little carbonate sediments accumulated in the Barents Sea and in the Sverdrup Basin, where the deep-to shallow-water sedimentary spectrum was occupied by siliceous sponge spicules. By that time, biogenic silica sedimentation was common throughout the world. Silica factories collapsed in the Late Permian, abruptly bringing the PCE to an end. In northwest Pangea, the end-Permian collapse of the PCE was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions. Chert deposition resumed in the distal oceanic areas during the early Middle Triassic (Anisian) after a 8^10 Ma interruption (Early Triassic Chert Gap). The conditions necessary for the onset, expansion and zenith of the PCE were provided by the thermohaline circulation of nutrient-rich cold waters along the northwestern and western margin of Pangea, and possibly throughout the world oceans. These conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area, created a nutrient-and oxygen-rich environment favouring siliceous biogenic productivity, established cold sea-floor conditions, hindering silica dissolution, while increasing calcium carbonate solubility, and provided conditions adverse to organic and inorganic carbonate production. The northwest margin of Pangea was, for nearly 30 Ma, bathed by cold waters presumably derived from the seasonal melting of northern sea ice, the assumed engine for thermohaline circulation.This process started near the Sakmarian^Artinskian boundary, intensified throughout Middle and Late Permian time and ceased suddenly in latest Permian time. It led to oceanic conditions much colder than normally expected from the palaeolatitudes, and the influence of cold northerly-derived water was felt as far south southern Nevada. The demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warm...

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Section: Prior To Pce: Sakmarian and Earliermentioning

confidence: 99%

Section: Expansion Of Pce: Guadalupianmentioning

confidence: 99%

Growth and demise of Permian biogenic chert along northwest Pangea: evidence for end-Permian collapse of thermohaline circulation

Beauchamp

Baud

2002

Palaeogeography, Palaeoclimatology, Palaeoecology

272

132

View full text Add to dashboard Cite

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“…2; Moore et al, 1994). The rocks overlying this unconformity consist of eight megasequences, each coinciding with a major phase of basin evolution (Hubbard et al, 1987).…”

Section: Regional Geologymentioning

confidence: 99%

“…The Beaufortian sequence comprises Jurassic through early Cretaceous rocks overlain by a Lower Cretaceous unconformity (LCu; fig. 2; Moore et al, 1994).…”

Section: Regional Geologymentioning

confidence: 99%