Geology Reports⌕ Search

Geology topics

A. R. Niem

Publications and source records attributed to A. R. Niem.

8 recordsLinked to original sources
USGS2011

Landslide stability: Role of rainfall-induced, laterally propagating, pore-pressure waves

The Johnson Creek Landslide is a translational slide in seaward-dipping Miocene siltstone and sandstone (Astoria Formation) and an overlying Quaternary marine terrace deposit. The basal slide plane slopes sub-parallel to the dip of the Miocene rocks, except beneath the back-tilted toe block, where it slopes inland. Rainfall events raise pore-water pressure in the basal shear zone in the form of pulses of water pressure traveling laterally from the headwall graben down the axis of the slide at rates of 1-6 m/hr. Infiltration of meteoric water and vertical pressure transmission through the unsaturated zone has been measured at ~50 mm/hr. Infiltration and vertical pressure transmission were too slow to directly raise head at the basal shear zone prior to landslide movement. Only at the headwall graben was the saturated zone shallow enough for rainfall events to trigger lateral pulses of water pressure through the saturated zone. When pressure levels in the basal shear zone exceeded thresholds defined in this paper, the slide began slow, creeping movement as an intact block. As pressures exceeded thresholds for movement in more of the slide mass, movement accelerated, and differential displacement between internal slide blocks became more pronounced. Rainfall-induced pore-pressure waves are probably a common landslide trigger wherever effective hydraulic conductivity is high and the saturated zone is located near the surface in some part of a slide. An ancillary finding is apparently greater accuracy of grouted piezometers relative to those in sand packs for measurement of pore pressures at the installed depth.

Environmental & Engineering Geoscience↗
USGS2001

Geologic map and database of the Roseburg 30' x 60' quadrangle, Douglas and Coos Counties, Oregon

The Roseburg 30' x 60' Quadrangle covers the southeastern margin of the Oregon Coast Range and its tectonic boundary with Mesozoic terranes of the Klamath Mountains (see figures 1 and 2 in pamphlet, also shown on map sheet). The geologic framework of the Roseburg area was established by the pioneering work of Diller (1898), Wells and Peck, (1961) and Ewart Baldwin (1974) and his students (see figure 3 in pamphlet, also shown on map sheet). Baldwin and his students focussed on the history of the Eocene Tyee basin, where the sediments lap across the tectonic boundary with the Mesozoic terranes and record the accretion of the Coast Range basement to the continent. Others have examined the sedimentary fill of the Tyee basin in detail, recognizing the deep marine turbidite facies of the Tyee Formation (Snavely and others, 1964) and proposing several models for the Eocene evolution of the forearc basin (Heller and Ryberg, 1983; Chan and Dott, 1983; Heller and Dickinson, 1985; Molenaar, 1985; see Ryu and others, 1992 for a comprehensive summary). Along the eastern margin of the quadrangle, both the Tyee basin and the Klamath terranes are overlain by Eocene volcanic rocks of the Western Cascade arc (Walker and MacLeod, 1991). The thick Eocene sedimentary sequence of the Tyee basin has significant oil and gas potential (Armentrout and Suek, 1985; Gautier and others, 1993; Ryu and others, 1996). Although 13 deep test wells have been drilled in the Roseburg quadrangle (see figure 2 and table 1 in pamphlet, also shown on map sheet), exploration to date has been hampered by an incomplete understanding of the basin�s tectonic setting and evolution. In response, the Oregon Department of Geology and Mineral Industries (DOGAMI) initiated a five year assessment of the oil and gas potential of the Tyee basin. This map is a product of a cooperative effort by the U. S. Geological Survey, Oregon State University, and DOGAMI to systematically map the sedimentary facies and structure of the Tyee basin. New geologic mapping of twenty-eight 7.5' quadrangles is summarized on the map (see figure 3, also shown on map sheet), and the digital database contains geologic information suitable for both 1:100K and 1:24K scale analysis. DOGAMI has published a compilation and synthesis of previous mapping (Niem and Niem, 1990), a basin-wide sequence stratigraphic model and correlations (Ryu and others, 1992), and a report on the oil and gas potential (Ryu and others, 1996). Readers interested in the oil and gas potential of the Roseburg quadrangle should use the map in combination with Ryu and others (1996) to address specific stratigraphic units and structural plays. Stratigraphic terminology for the Tyee basin adopts the type sections, formation names, and framework of Ryu and others (1992, 1996), which were developed concurrently with the mapping and are recognized throughout the basin. For detailed discussion of nomenclature, type sections, lithology, thickness and distribution, age, contact relationships, and depositional environment of stratigraphic units, the reader is referred to Ryu and others (1992). In this report we focus on the spatial, temporal, and structural relationships between units revealed by geologic mapping. Map unit ages (see figure 4 in pamphlet, also shown on map sheeet) are adjusted slightly from Ryu and others (1992, 1996) to fit new coccolith age determinations (D. Bukry, cited in pamphlet), paleomagnetic polarity data (Simpson, 1977 and new data cited in pamphlet), and the time scale of Berggren and others (1995).

Oregon↗
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↗