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N. S. MacLeod

Publications and source records attributed to N. S. MacLeod.

33 records · Page 2Linked to original sources
USGS1980

Makah Formation — A deep-marginal-basin sequence of late Eocene and Oligocene age in the northwestern Olympic Peninsula, Washington

The Makah Formation of the Twin River Group crops out in a northwest-trending linear belt in the northwesternmost part of the Olympic Peninsula, Wash. This marine sequence consists of 2800 meters of predominantly thin-bedded siltstone and sandstone that encloses six distinctive newly named members--four thick-bedded amalgamated turbidite sandstone members, an olistostromal shallow-water marine sandstone and conglomerate member, and a thin-bedded water-laid tuff member. A local unconformity of submarine origin occurs within the lower part of the Makah Formation except in the central part of the study area, where it forms the contact between the older Hoko River Formation and the Makah. Foraminiferal faunas indicate that the Makah Formation ranges in age from late Eocene (late Narizian) to late Oligocene (Zemorrian) and was deposited in a predominantly lower to middle bathyal environment. The Makah Formation is part of a deep-marginalbasin facies that crops out in the western part of the Olympic Peninsula, in southwesternmost Washington and coastal embayments in northwestern Oregon, and along the central part of the coast of western Vancouver Island. On the basis of limited subsurface data from exploratory wells, correlative deep-marginal-basin deposits underlie the inner continental shelf of Oregon and the continental shelf (Tofino basin) along the southwestern side of Vancouver Island. Directional structures in the Makah Formation indicate that the predominantly lithic arkosic sandstone that forms the turbidite packets was derived from the northwest. A possible source of the clastic material is the dioritic, granitic, and volcanic terranes in the vicinity of the Hesquiat Peninsula and Barkley Sound on the west coast of Vancouver Island. Vertical and lateral variations of turbidite facies suggest that the four packets of sandstone were formed as depositional lobes on an outer submarine fan. The thin-bedded strata between the turbidite packets have characteristics of basin-plain and outer-fan fringe deposits.

Washington↗
USGS1979

Makah Formation--a deep marginal basin sedimentary sequence of Late Eocene and Oligocene age in the northwestern Olympic Peninsula, Washington

The Makah Formation of the Twin River Group crops out in a north-west-trending linear belt in the northwesternmost part of the Olympic Peninsula, Wash. This marine sequence consists of 2,800 meters of predominantly thin-bedded siltstone and sandstone that encloses six distinctive members. The named members include four packets of thick-bedded amalgamated turbidite sandstone, an olistostromal shallow-water marine sandstone and conglomerate member, and a thin-bedded water-laid tuff member. A local unconformity of submarine origin occurs within the lower part of the Makah Formation except in the central part of the study area, where it forms the contact between the older Hoko River Formation and the Makah. Foraminiferal faunas indicate that the Makah Formation ranges in age from late Eocene (late Narizian Stage) to late Oligocene (Zemorrian Stage) and was deposited in a predominantly lower to middle bathyal environment. The Makah strata are part of a deep marginal basin facies that crops out in the western part of the Olympic Peninsula, in southwesternmost Washington and coastal embayments in northwestern Oregon, and along the central part of the coast of western Vancouver Island. On the basis of limited subsurface data from exploratory wells, correlative deepmarginal-basin deposits underlie the inner continental shelf of Oregon and the continental shelf (Tofino Basin) along the southwestern side of Vancouver Island. Directional structures in the Makah Formation indicate that the predominantly lithic arkosic sandstone that forms the turbidite packets was derived from the northwest. A possible source of the clastics is the dioritic, granitic, and volcanic terranes in the vicinity of the Hesquiat Peninsula on the west coast of Vancouver Island. Vertical and lateral variations of turbidite facies suggest that the four packets of sandstone were formed as depositional lobes on an outer submarine fan. The thin-bedded strata between the turbidite packets have characteristics of basin-plain and outer-fan fringe deposits.

Washington↗
USGS1973

Age and tectonic implications of some low-grade metamorphic rocks from the Yucatan Channel

Phyllite and marble dredged from the lower part of the continental slope between Cuba and the Yucatan Peninsula seem to support the contention that a pre-early Tertiary metamorphic belt extends from the western Greater Antilles into northern Central America. The minimum K-Ar ages derived from the samples suggest that the metamorphic event was pre-Late Cretaceous, and evaluation of the K-Ar data implies that this metamorphic event is not older than Late Jurassic. Greater antiquity, however, is inferred from structural and stratigraphic relations in British Honduras, where the latest regional metamorphic event was post-Early Permian and pre-Middle Jurassic. Rifting and extension related to plate motions along the British Honduras Quintana Roo margin through Mesozoic and earliest Cenozoic time presumably would preclude extensive regional metamorphism, permitting only limited development of schistose rocks there during that interval. The timing of metamorphic events in western Cuba is uncertain, but a pre-Middle Jurassic episode possibly is reflected in the phyllite and marble terranes of Isla de Pinos and Sierra de Trinidad. Local incipient metamorphism of Early and Middle Jurassic strata in the Sierra de los Organos may have resulted from severe tectonism that began in Late Cretaceous time and diminished in the Eocene.

Yucatan Channel↗