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Coordinates: 44°54′N 123°24′W / 44.9°N 123.4°W / 44.9; -123.4
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{{short description|A sequence of basaltic pillow lavas that make up part of Siletzia}}
{{short description|Sequence of basaltic pillow lavas that make up part of Siletzia}}
{{Infobox rockunit
⚫
[[Image:OregonCoastRangeRocks.JPG|thumb|250px|Exposed [[pillow lava]] in the Northern range.]]
| name = Siletz River Volcanics
The '''Siletz River Volcanics''', located in the [[Oregon Coast Range]], [[United States]], are a sequence of [[basalt]]ic [[pillow lava]]s that make up part of [[Siletzia]]. The basaltic pillow lavas originally came from [[submarine volcano]]es that existed during the [[Eocene]].
| image = OregonCoastRangeRocks.JPG
⚫
| caption = Exposed [[pillow lava]] in the Northern range
| type = [[Formation (stratigraphy)|Formation]]
| age = [[Selandian]]-[[Ypresian]] ([[Tiffanian]]-[[Bridgerian]])<br>{{fossil range|59.6|47.6}}
| period = Thanetian
| prilithology = [[Sill (geology)|Sills]] of [[Tholeiite|tholeitic]] to [[Alkali basalt|alkalic basalt]]s
| otherlithology = [[Tuff]]-[[breccia]], [[siltstone]], [[sandstone]]
| namedfor = [[Siletz River]]
| namedby =
| year_ts =
| region = [[Benton County, Oregon|Benton]], [[Coos County, Oregon|Coos]], [[Douglas County, Oregon|Douglas]], [[Lane County, Oregon|Lane]], [[Lincoln County, Oregon|Lincoln]], [[Polk County, Oregon|Polk]], [[Tillamook County, Oregon|Tillamook]], [[Washington County, Oregon|Washington]] & [[Yamhill County, Oregon|Yamhill Counties]], [[Oregon]]
| country = {{USA}}
| coordinates = {{coord|44.9|N|123.4|W|display=inline,title}}
| paleocoordinates = {{coord|47.0|N|107.5|W|display=inline}}
| unitof =
| subunits =
| underlies = [[Yamhill Formation]]
| overlies =
| thickness =
| extent =
| area =
| map = {{Location map+ | United States#Oregon
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | United States#Oregon
| lat_deg = 44.9
| lon_deg = -123.4
| mark = Orange ff8040 pog.svg
| marksize = 12
}}
}}
| map_caption =
}}
The '''Siletz River Volcanics''', located in the [[Oregon Coast Range]], United States, are a sequence of [[basalt]]ic [[pillow lava]]s that make up part of [[Siletzia]].<ref name=FW>[http://www.fossilworks.org/cgi-bin/bridge.pl?action=displayStrata&geological_group=&formation=Siletz%20River%20Volcanics%20&group_formation_member=Siletz%20River%20Volcanics%20 Siletz River Volcanics] at [[Fossilworks]].org</ref><ref name=USGS>{{cite web |url=https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=ORTsr%3B0 |title=Siletz River Volcanics and related rocks |work=USGS Mineral Resources On-Line Spatial Data |publisher=[[United States Geological Survey|U.S. Geological Survey]] }}</ref> The basaltic pillow lavas originally came from [[submarine volcano]]es that existed during the [[Eocene]].


== Description ==
The [[Paleocene]] to [[Eocene]] volcanics consist of [[volcanism]] flows and [[Sill (geology)|sills]] of [[Tholeiite|tholeitic]] to [[Alkali basalt|alkalic basalt]]s with associated [[tuff]]-[[breccia]], [[siltstone]] and [[sandstone]]. The flows are [[Vesicular texture|vesiculated]] with [[zeolite]] filled amygdules.
The [[Paleocene]] to [[Eocene]] volcanics consist of [[volcanism]] flows and [[Sill (geology)|sills]] of [[Tholeiite|tholeitic]] to [[Alkali basalt|alkalic basalt]]s with associated [[tuff]]-[[breccia]], [[siltstone]] and [[sandstone]]. The flows are [[Vesicular texture|vesiculated]] with [[zeolite]] filled amygdules.


The volcanics originated as [[oceanic crust]] and [[seamounts]]. [[Potassium argon dating]] gives an age of 50.7 ± 3.1 to 58.1 ± 1.5 Ma.<ref name=USGS>{{cite web |url=https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=ORTsr%3B0 |title=Siletz River Volcanics and related rocks |work=USGS Mineral Resources On-Line Spatial Data |publisher=[[United States Geological Survey|U.S. Geological Survey]] }}</ref>
The volcanics originated as [[oceanic crust]] and [[seamounts]]. [[Potassium argon dating]] gives ages of 58.1 ± 1.5 to 50.7 ± 3.1 Ma; [[Selandian]] to [[Ypresian]].<ref name=USGS/>


The sequence has been divided into a lower pillowed tholeiitic unit and an upper [[porphyritic]] alkali basalt unit.<ref>{{Cite journal |first=Parke D. |last=Snavely |first2=Norman S. |last2=MacLeod |first3=Holly C. |last3=Wagner |title=Tholeiitic and alkalic basalts of the Eocene Siletz River Volcanics, Oregon Coast Range |journal=American Journal of Science |volume=266 |issue=6 |date=June 1968 |pages=454–481 |url=http://www.ajsonline.org/cgi/content/abstract/266/6/454 |doi=10.2475/ajs.266.6.454}}</ref>
The sequence has been divided into a lower pillowed tholeiitic unit and an upper [[porphyritic]] alkali basalt unit.<ref name=Snavely1968>Snavely et al., 1968</ref>


The volcanics occur in the following counties of western [[Oregon]]: [[Benton County, Oregon|Benton]], [[Coos County, Oregon|Coos]], [[Douglas County, Oregon|Douglas]], [[Lane County, Oregon|Lane]], [[Lincoln County, Oregon|Lincoln]], [[Polk County, Oregon|Polk]], [[Tillamook County, Oregon|Tillamook]], [[Washington County, Oregon|Washington]] and [[Yamhill County, Oregon|Yamhill]].<ref name=USGS/>
The volcanics occur in the following counties of western [[Oregon]]: [[Benton County, Oregon|Benton]], [[Coos County, Oregon|Coos]], [[Douglas County, Oregon|Douglas]], [[Lane County, Oregon|Lane]], [[Lincoln County, Oregon|Lincoln]], [[Polk County, Oregon|Polk]], [[Tillamook County, Oregon|Tillamook]], [[Washington County, Oregon|Washington]] and [[Yamhill County, Oregon|Yamhill]].<ref name=USGS/>


=== Fossil content ===
⚫
==References==
The sedimentary beds at the Ellendale Basalt and Portland Cement Company Quarries, interbeds in the upper part of the Siletz River volcanics, have provided fossils of the [[Archaeogastropoda|archaeogastropods]] ''[[Pleurotomaria|Pleurotomaria (Entemnotrochus) baldwini]]'', ''[[Pleurotomaria|P. (E.) schencki]]'' and ''[[Pleurotomaria|P. (E.) siletzensis]]''.<ref name=Hickman1976>Hickman, 1976</ref>
⚫
{{Reflist}}


== See also ==
{{div col}}
* [[Coldwater Beds]] of British Columbia
* [[Golden Valley Formation]] of North Dakota
* [[Hanna Formation]] of Wyoming
* [[Indian Meadows Formation]] of Wyoming
* [[Margaret Formation]] of Ellesmere Island, Northwest Territories and Nunavut
* [[Nanjemoy Formation]] of Virginia, Maryland and District of Columbia
* [[Paskapoo Formation]] of Alberta
* [[Wasatch Formation]] of [[Colorado]], [[Idaho]], [[Montana]], [[New Mexico]], [[Wyoming]] and [[Utah]]
* [[Washakie Formation]] of Colorado and Wyoming
* [[Willwood Formation]] of Wyoming
{{div col end}}

⚫
== References ==
⚫
{{Reflist|3}}

=== Bibliography ===
* {{citation |last=Hickman |first=C.S |year=1976 |title=Pleurotomaria (Archaeogastropoda) in the Eocene of the northeastern Pacific: a review of Cenozoic biogeography and ecology of the genus |journal=[[Journal of Paleontology]] |volume=50 |pages=1090–1102}}
* {{citation |first1=Parke D. |last1=Snavely |first2=Norman S. |last2=MacLeod |first3=Holly C. |last3=Wagner |year=1968 |title=Tholeiitic and alkalic basalts of the Eocene Siletz River Volcanics, Oregon Coast Range |url=http://www.ajsonline.org/cgi/content/abstract/266/6/454 |journal=[[American Journal of Science]] |volume=266 |issue=6 |pages=454–481 |doi=10.2475/ajs.266.6.454|bibcode=1968AmJS..266..454S }}

== Further reading ==
* Baldwin, E.M., 1974, Eocene stratigraphy of southwestern Oregon: Oregon Department of Geology and Mineral Industries Bulletin 83, 40 p.
* Duncan, R.A., 1982, A captured island chain in the coast Range of Oregon and Washington: Journal of Geophysical Research, v. 87, p. 10, 827–10, 837
* Snavely, P.D., MacLeod, N.S., and Wagner, H.C., 1973, Miocene tholeiitic basalts of coastal Oregon and Washington and their relations to coeval basalts of the Columbia Plateau: Geological Society of America Bulletin, v. 84, p. 387–424

[[Category:Paleogene geology of Oregon]]
[[Category:Volcanism of Oregon]]
[[Category:Volcanism of Oregon]]
[[Category:Volcanoes of Oregon]]
[[Category:Paleocene volcanism]]
[[Category:Seamounts of the Pacific Ocean]]
[[Category:Paleocene Series of North America]]
[[Category:Paleocene volcanoes]]
[[Category:Selandian Stage]]
[[Category:Eocene volcanoes]]
[[Category:Thanetian Stage]]
[[Category:Bridgerian]]
[[Category:Tiffanian]]
[[Category:Wasatchian]]
[[Category:Eocene volcanism]]
[[Category:Eocene Series of North America]]
[[Category:Ypresian Stage]]
[[Category:Oregon Coast Range]]
[[Category:Oregon Coast Range]]
[[Category:Yellowstone hotspot]]
[[Category:Yellowstone hotspot]]
[[Category:Seamounts of the Pacific Ocean]]

[[Category:Siltstone formations]]
{{Oregon-geo-stub}}
[[Category:Sandstone formations of the United States]]
{{volcanology-stub}}
[[Category:Tuff formations]]
[[Category:Paleontology in Oregon]]
[[Category:Landforms of Benton County, Oregon|Formations]]
[[Category:Landforms of Coos County, Oregon|Formations]]
[[Category:Landforms of Douglas County, Oregon|Formations]]
[[Category:Landforms of Lane County, Oregon|Formations]]
[[Category:Landforms of Lincoln County, Oregon|Formations]]
[[Category:Landforms of Polk County, Oregon|Formations]]
[[Category:Landforms of Tillamook County, Oregon|Formations]]
[[Category:Landforms of Washington County, Oregon|Formations]]
[[Category:Landforms of Yamhill County, Oregon|Formations]]
[[Category:Volcanoes of Oregon]]
[[Category:Volcanoes of the United States]]

Revision as of 23:02, 16 July 2024

Siletz River Volcanics
Stratigraphic range: Selandian-Ypresian (Tiffanian-Bridgerian)
59.6–47.6 Ma
Exposed pillow lava in the Northern range
TypFormation
UnderliesYamhill Formation
Lithology
PrimäreSills of tholeitic to alkalic basalts
OtherTuff-breccia, siltstone, sandstone
Standort
Coordinates44°54′N 123°24′W / 44.9°N 123.4°W / 44.9; -123.4
Approximate paleocoordinates47°00′N 107°30′W / 47.0°N 107.5°W / 47.0; -107.5
RegionBenton, Coos, Douglas, Lane, Lincoln, Polk, Tillamook, Washington & Yamhill Counties, Oregon
Land Vereinigte Staaten
Type section
Named forSiletz River
Siletz River Volcanics is located in the United States
Siletz River Volcanics
Siletz River Volcanics (the United States)
Siletz River Volcanics is located in Oregon
Siletz River Volcanics
Siletz River Volcanics (Oregon)

The Siletz River Volcanics, located in the Oregon Coast Range, United States, are a sequence of basaltic pillow lavas that make up part of Siletzia.[1][2] The basaltic pillow lavas originally came from submarine volcanoes that existed during the Eocene.

Description

The Paleocene to Eocene volcanics consist of volcanism flows and sills of tholeitic to alkalic basalts with associated tuff-breccia, siltstone and sandstone. The flows are vesiculated with zeolite filled amygdules.

The volcanics originated as oceanic crust and seamounts. Potassium argon dating gives ages of 58.1 ± 1.5 to 50.7 ± 3.1 Ma; Selandian to Ypresian.[2]

The sequence has been divided into a lower pillowed tholeiitic unit and an upper porphyritic alkali basalt unit.[3]

The volcanics occur in the following counties of western Oregon: Benton, Coos, Douglas, Lane, Lincoln, Polk, Tillamook, Washington and Yamhill.[2]

Fossil content

The sedimentary beds at the Ellendale Basalt and Portland Cement Company Quarries, interbeds in the upper part of the Siletz River volcanics, have provided fossils of the archaeogastropods Pleurotomaria (Entemnotrochus) baldwini, P. (E.) schencki and P. (E.) siletzensis.[4]

See also

References

  1. ^ Siletz River Volcanics at Fossilworks.org
  2. ^ a b c "Siletz River Volcanics and related rocks". USGS Mineral Resources On-Line Spatial Data. U.S. Geological Survey.
  3. ^ Snavely et al., 1968
  4. ^ Hickman, 1976

Bibliography

Further reading

  • Baldwin, E.M., 1974, Eocene stratigraphy of southwestern Oregon: Oregon Department of Geology and Mineral Industries Bulletin 83, 40 p.
  • Duncan, R.A., 1982, A captured island chain in the coast Range of Oregon and Washington: Journal of Geophysical Research, v. 87, p. 10, 827–10, 837
  • Snavely, P.D., MacLeod, N.S., and Wagner, H.C., 1973, Miocene tholeiitic basalts of coastal Oregon and Washington and their relations to coeval basalts of the Columbia Plateau: Geological Society of America Bulletin, v. 84, p. 387–424
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