| Creator |
|
|---|
| Abstract |
- Twelve rock units, from upper Eocene to middle Miocene are exposed in the Nicolai Mountain-Gnat Creek area. They are, from oldest to youngest: Pittsburg Bluff Formation; Oswald West mudstone; Big Creek sandstone, upper Silver Point mudstone, and
Pipeline mudstone members of the Astoria Formation; Depoe Bay Basalt; Grande Ronde Basalt; Cape Foulweather Basalt; and
sandstone correlative to the Vantage Member of the Ellensburg Formation; Frenchman Springs Member of the Wanapum Basalt; Clifton, Formation (defined by author); and Pomona Member of the Saddle Mountains Basalt.
Upper Eocene Pittsburg Bluff Formation is a fine-grained sandstone and laminated siltstone deposited in an inner to middle continental shelf environment. Concordant onlapping by the upper Oligocene, middle shelf to upper slope glauconitic Oswald West mudstone, establishes a tie between the
northeastern and northwestern Oregon Coast Range stratigraphies. The lower to middle Miocene Astoria Formation represents another marine onlap sequence, beginning with the fine-grained cross-bedded inner shelf Big Creek sandstone member. The overlying laminted upper Silver Point and Pipeline mudstone members were deposited in a deepening middle shelf to upper slope environment. The middle Miocene tholeiitic basalts extruded from two sources. Grande Ronde, Frenchman Springs, and Pomona basalts
of the Columbia River Group erupted from fissures east of the Cascades and flowed down an ancestral Columbia River valley entering the sea in the study area. Simultaneously,
petrologically similar but less voluminous Depoe Bay and Cape Foulweather are correlative to the low MgO Grande Ronde and
Frenchman Springs in the study area. Abundant dikes and sills and the bathyal mudstone interbeds suggest that the coastal pillow basalts extruded locally onto the sea floor. Subaerial plateau-derived flows are associated with cross-bedded, fluvial to shallow marine arkosic sandstone interbeds. Some of these subaerial lavas flowed into the sea, forming "lava deltas" of foreset pillow palagonite and possibly "invasive" sills. The
basalt stratigraphy allows a nearly flow by flow correlation of Grande Ronde and Frenchman Springs units from the Clackamas
River area (Western Cascades) into this study area. The presence of Pomona Member in this area is the first substantiated recognition of this petrologically and chemically
distinctive subaerial flow in northwestern Oregon. The 200-meter thick Clifton formation (previously called the Pliocene (?) sandstone at Clifton) is now dated by diatom assemblages and stratigraphic position as middle Miocene in age. Three lithofacies are recognized. Facies 1, at the base and top of the unit, is an arkosic, fine- to coarse- grained sandstone with cross-bedding, vertical Rosselia burrows, lignitic coal beds, and rare molluscan shells. It represents a river mouth and shallow marine offshore bar deposit. Facies 2, in the middle of the formation, consitst of well-laminated
diatom-bearing carbonaceous and micaceous shelf/slope siltstones with thin fine-grained turbidite sandstones. Facies consists of channelized siltstone breccias, chaotic debris flows, thick amalgamated arkosic grain flows, structureless sandstones, and minor volcanic pebble conglomerates. These lithologies suggest a canyon head and slump deposit formed as a submarine channel cut into the shelf/slope siltstones of Facies
2. Sandstone petrography and grain size analyses indicate that the detritus of the Clifton and other sandstones in the area
was derived from acid igneous, metamorphic, and intermediate volcanic provenances similar to those drained by the Columbia
River today. Despite high measured permeabilities, breaching limits the reservoir potential of the sandstone. Mudstone units are immature to mature hydrocarbon source rocks. A potential for
gas exists in the Cowlitz or its equivalent in the subsurface and in the Clifton channel sandstones projected into the offshore area.
|
|---|
| Resource Type |
|
|---|
| Date Available |
|
|---|
| Date Issued |
|
|---|
| Degree Level |
|
|---|
| Degree Name |
|
|---|
| Degree Field |
|
|---|
| Degree Grantor |
|
|---|
| Commencement Year |
|
|---|
| Advisor |
|
|---|
| Academic Affiliation |
|
|---|
| Non-Academic Affiliation |
|
|---|
| Subject |
|
|---|
| Rights Statement |
|
|---|
| Publisher |
|
|---|
| Language |
|
|---|
| Digitization Specifications |
- Master files scanned at 600 ppi (256 Grayscale, 24-bit Color) using Capture Perfect 3.0 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B&W, 24-bit Color), using Capture Perfect 3.0, on a Canon DR-9080C. CVista PdfCompressor 3.1 was used for pdf compression and textual OCR.
|
|---|
| Replaces |
|
|---|
| Additional Information |
- description.provenance : Submitted by Anna Opoien (aoscanner@gmail.com) on 2008-07-16T01:04:56Z
No. of bitstreams: 4
Murphy_Thomas_M_1981_Plate2.jpg: 1421845 bytes, checksum: 940ace96f4e2ec39abcce9db790261d8 (MD5)
Murphy_Thomas_M_1981.pdf: 5684531 bytes, checksum: c14c19a0fde7694a5066e9726ecb840c (MD5)
Murphy_Thomas_M_1981_Plate1.jpg: 2128038 bytes, checksum: 843a124b0af1c697f471410861eb0eb0 (MD5)
Murphy_Thomas_M_1981_Plate3.jpg: 1403288 bytes, checksum: 6df0c9d8c43a54362dc31bfb7010c25a (MD5)
- description.provenance : Made available in DSpace on 2008-07-16T15:45:48Z (GMT). No. of bitstreams: 4
Murphy_Thomas_M_1981_Plate2.jpg: 1421845 bytes, checksum: 940ace96f4e2ec39abcce9db790261d8 (MD5)
Murphy_Thomas_M_1981.pdf: 5684531 bytes, checksum: c14c19a0fde7694a5066e9726ecb840c (MD5)
Murphy_Thomas_M_1981_Plate1.jpg: 2128038 bytes, checksum: 843a124b0af1c697f471410861eb0eb0 (MD5)
Murphy_Thomas_M_1981_Plate3.jpg: 1403288 bytes, checksum: 6df0c9d8c43a54362dc31bfb7010c25a (MD5)
- description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2008-07-16T15:43:58Z (GMT) No. of bitstreams: 4
Murphy_Thomas_M_1981_Plate2.jpg: 1421845 bytes, checksum: 940ace96f4e2ec39abcce9db790261d8 (MD5)
Murphy_Thomas_M_1981.pdf: 5684531 bytes, checksum: c14c19a0fde7694a5066e9726ecb840c (MD5)
Murphy_Thomas_M_1981_Plate1.jpg: 2128038 bytes, checksum: 843a124b0af1c697f471410861eb0eb0 (MD5)
Murphy_Thomas_M_1981_Plate3.jpg: 1403288 bytes, checksum: 6df0c9d8c43a54362dc31bfb7010c25a (MD5)
- For master (tiff) digital images of maps contained in this document contact scholarsarchive@library.oregonstate.edu
- description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2008-07-16T15:45:47Z (GMT) No. of bitstreams: 4
Murphy_Thomas_M_1981_Plate2.jpg: 1421845 bytes, checksum: 940ace96f4e2ec39abcce9db790261d8 (MD5)
Murphy_Thomas_M_1981.pdf: 5684531 bytes, checksum: c14c19a0fde7694a5066e9726ecb840c (MD5)
Murphy_Thomas_M_1981_Plate1.jpg: 2128038 bytes, checksum: 843a124b0af1c697f471410861eb0eb0 (MD5)
Murphy_Thomas_M_1981_Plate3.jpg: 1403288 bytes, checksum: 6df0c9d8c43a54362dc31bfb7010c25a (MD5)
|
|---|
