Continuous seismic profiling investigation of the southern Oregon continental shelf between Cape Blanco and Coos Bay

Mackay, Angus James

doi:10.3133/ofr69156

Cited by 2 publications

(5 citation statements)

References 12 publications

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“…The Port Qrford shear zone zone cannot be traced far into the offshore and was not identified, as such, in this study; Mackay (1969) may have crossed the zone about 10 km north of Cape Blanco, but speculated that it is covered by post-Miocene strata farther northwest on the shelf. However, it is also possible that shear associated with this zone is transferred to other northwest trending faults in the offshore, perhaps those here described as showing evidence of Quaternary offset north of Cape Arago and on Heceta Bank.…”

Section: Faultsmentioning

confidence: 73%

“…Cbquille Bank is a north-trending, asymmetrical, doubly plunging anticline (Mackay, 1969). The west side is inferred by Kulm and Fowler (1974b) to be faulted down, based on bathymetry and on the absence there of the thick Pliocene-Pleistocene section present on the east lint>.…”

Section: Generalmentioning

confidence: 97%

“…thesis of A. J. Mackay (1969), who mapped the inner shelf between Cape Arago and Coquille Point using a closely spaced network of seismic reflection lines. Ihe geology of the adjacent area on land has been mapped and described by Alien and Baldwin (1944), Wells and Peck (1961), Ramp (1972), Beaulieu (1973), Schlicker andDeacon (1974), and Beaulieu and Hughes (1975).…”

Section: Marine Geology Of Coos Bay Basinmentioning

confidence: 99%

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Reconnaissance geology and geologic hazards of offshore Coos Bay basin, central Oregon continental margin

Clarke¹,

Field²,

Hirozawa³

1981

Open-File Report

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Major geologic and physiographic features of 5 the continental margin of the Pacific northwest. Correlation chart of major Tertiary units in 7 western Oregon. Area of the offshore Coos Bay basin. 11 High resolution seismic reflection record (77-05) 13 extending eastward across Heceta Bank and the adjacent shelf. High resolution seismic reflection record (78-42) 14 extending eastward from Heceta Bank across the adjacent shelf. High resolution seismic reflection record (78-32) 16 across the inner shelf north of Cape Arago. Deep penetration seismic reflection record (78-38) 17 across shelf and slope between Heceta Bank and Cape Arago. Deep penetration seismic reflection record (7$-40) 22 across inner shelf southeast of Heceta Bank. Deep penetration (a) and high resolution (b) seismic 24 reflection records (77-14) across slope northwest of Cape Arago. Deep penetration seismic reflection record (77-22) 27 across shelf and slope north of Coquille Bank. Deep penetration (a) and high resolution (b) seismic 30 reflection records (77-18) across outer shelf and slope west of Cape Arago. Deep penetration seismic reflection profile (78-30) 31 across shelf and upper slope west of Cape Arago.

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Section: Faultsmentioning

confidence: 73%

Section: Generalmentioning

confidence: 97%

Section: Marine Geology Of Coos Bay Basinmentioning

confidence: 99%

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Reconnaissance geology and geologic hazards of offshore Coos Bay basin, central Oregon continental margin

Clarke¹,

Field²,

Hirozawa³

1981

Open-File Report

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“…The offshore extension of the Port Orford shear zone was not identified in this study. Although Mackay (1969) may have crossed this zone about 10 km north of Cape Blanco, he speculated that it is covered by post-Miocene strata farther northwest on the shelf. However, shear associated with this zone may also be transferred to other northwest-trending faults in the offshore, such as those mapped during this study north of Cape Arago and on Heceta Bank that show evidence of Quaternary offset.…”

Section: Faultsmentioning

confidence: 99%

“…The geology of the central Oregon offshore has been mapped on a regional scale by members of the Oregon State University Department of Oceanography; their findings were presented in a series of theses and technical reports (notably Kulm, 1969;Kulm and Fowler, 1970;Fowler and Kulm, 1971) and were summarized by Kulm and Fowler (1974a, b). Mackay (1969) mapped the inner shelf between Cape Arago and Coquille Point, using a closely spaced network of single-channel seismic-reflection lines. Interpretive geologic cross sections were constructed across the offshore Coos Bay basin in the vicinity of Heceta and Coquille Banks by Couch and Braman (1980) and Couch and Pitts (1980), using combined gravity, magnetic, seismic, and well data.…”

mentioning

confidence: 99%

Reconnaissance geology and geologic hazards of the offshore Coos Bay basin, Oregon

Clarke¹,

Field²,

Hirozawa³

1985

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The offshore Coos Bay basin underlies the continental shelf and upper slope between Heceta Bank and Coquille Bank, Oregon, and comprises a succession of middle Eocene and younger principally marine sedimentary rocks 5,000+ m thick. Three acoustic units have been defined within this basin on the basis of seismic-reflection and sampling data: acoustic unit 1, inferred to be Quaternary in age and to be a maximum of about 500 m thick, is widespread on the continental shelf and slope; acoustic unit 2., inferred to be late Miocene to late Pliocene in age, is exposed on Heceta Bank, on the inner shelf between Cape Blanco and Cape Arago, and, locally, in breached anticlines; and acoustic unit 3, inferred to comprise strata of Eocene to middle Miocene age, is exposed locally in breached anticlines on the inner and middle continental shelf and on the middle of the continental slope. Recurrent major episodes of deformation are evidenced by regional unconformities of late Pliocene to early Pleistocene, early late Miocene, and middle to late Eocene age; these unconformities probably reflect significant changes in the history of plate convergence along this margin. Potential geologic hazards to offshore development include groups of short north-to northwesttrending faults that cut Quaternary (locally Holocene) deposits on the continental shelf between Cape Arago and Heceta Bank. Seismic activity appears to be low within the offshore basin area; however, a significant possibility exists of damage from tsunamis, sea-floor mass movement, and liquefaction resulting from earthquakes in adjacent regions, notably the northern California continental margin. Unstable sea-floor conditions resulting from recent subaqueous slides and flows appear to be uncommon, although the presence of locally steep slopes and thick accumulations of unconsolidated sediment with unknown engineering characteristics make site-specific studies of sea-flool stability advisable. Buried zones as large as 190 km in area and 2.00 to 2.50 m thick of disrupted and rotated acoustic reflectors appear to record episodes of seafloor failure during Pleistocene low stands of sea level. Several folds showing sea-floor relief, one of which appears to be diapiric, reflect tectonic instability of the modern upper continental slope along the west margin of the basin. Acoustic anomalies suggestive of shallow g~ accumulations cover areas of as much as 12.0 km , and combined geophysical and ':II

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Continuous seismic profiling investigation of the southern Oregon continental shelf between Cape Blanco and Coos Bay

Cited by 2 publications

References 12 publications

Reconnaissance geology and geologic hazards of offshore Coos Bay basin, central Oregon continental margin

Reconnaissance geology and geologic hazards of offshore Coos Bay basin, central Oregon continental margin

Reconnaissance geology and geologic hazards of the offshore Coos Bay basin, Oregon

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