The Ore Bin - Oregon Department of Geology and Mineral Industries

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Figure 5. Pike Creek Formation at the mouth af Pike Creek Canyon. (Ore. Hwy. Div . photo) Figure 6. Kiger Gorge. Steens Basalt flaws are well disployed in the canyon walls. (Ore. Hwy . Div. photo) 56
Pike Creek Volcanic Series Fuller gave the name Pike Creek Volcanic Series to a thick series of acidic flows and stratified tuffs that are best exposed in Pike Creek Canyon (Figure 5). The aggregate thickness totals more than 1,500 feet. The lower 1,000 feet of the series consists of two tuff members interlayered with two rhyolite flows, each unit 200 to 300 feet thick. The lowermost tuff unit is intruded by five basalt sills ranging from a few inches to 15 feet in thickness. A 40-foot layer of tuff overlies the uppermost rhyolite, and this is in turn followed by two biotite-dacite flows, the lower of which is about 200 feet thick and the upper ranging from 200 feet to 500 feet. Walker (Walker and Repenning, 1965) renamed this series the Pike Creek Formation, to which he assigns an age of Oligocene and Miocene. Steens Mountain Andesitic Series This series consists of an andesite flow up to 200 feet or more in thickness at the base and capped by a stratified tuff unit up to 20 feet thick, a unit called the "great flow" with a maximum thickness of about 900 feet, and a series of alternating thin layers of andesite breccias and platy flowandesite with a maximum aggregate thickness of more than 600 feet. Pyroc lasHc deposits marking sites of small volcanic cones are related to the upper andesite series. The "great flow" is a prominent unit in the Alvord Creek locality, where it is about 900 feet thick. Joint columns measure as much as 5 feet across and rise 300 feet above the talus. The unit thins to about 500 feet in the valley of Cottonwood Creek, a mile to the north. Fuller did not identify the unit with certainty north of there, though he reports that similar rock with exposed thickness of about 400 feet crops out.at Mann Creek, abQUt 7 mi les north of Cottonwood Creek. South of Alvord Creek the flow is exposed only in scattered outcrops. . Steens Mountain Basalt The Steens Mountain Basalt (name shortened to Steens Basalt) (Figure 2), a series of thin flood or plateau basalt, constit.utes the bulk of the mountain and extends into Pueblo Mountain to the south and to Abert Rim to the west. It makes up the upper 3,000 feet of the east scarp and is the rock exposed along the glacial valleys on the back slope of the mountain. Except where covered locally by a younger ash flow, it is the bedrock over most of the western slope. The maximum original thickness of the Steens Basalt is not known, for much of it has been removed from the High Steens by glacial erosion, and it is only on the east scarp of this part of Steens Mountain that the base is exposed. Wilkerson (1958) measured 3,280 feet of section on the west rim 57
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Volume 38, No. I January 1976 STATE
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State of Oregon Department of Geolo
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The search for uranium was carried
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Although difficulties have been exp
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Table 1. Oil and gas drilling in Or
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GEOTHERMAL ACTIVITY IN 1975 Donald
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Richard Couch of Oregon State Unive
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Abandonment cementing operations at
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Table 5. Federal geothermal lease s
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21. Ferruginous bauxite and high-al
Page 23 and 24: 8. Geology of Greenhorn District, S
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Page 31 and 32: Figure 1. View of Mount Hood from s
Page 33: Recent Observations on Mount Baker
Page 36 and 37: A log of all anomalies has been mai
Page 38 and 39: Figure 6. Breakup of ice within cra
Page 40 and 41: Figure 8. Photo of East Breach area
Page 42 and 43: OUR CHANGING RESOURCE CLIMATE Ralph
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Page 51 and 52: Our research to determine heat flow
Page 59 and 60: ash-flow tuff. Regional heat flow i
Page 61 and 62: OPEN FI LE REPORTS ISSUED Oregon De
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Page 95 and 96: Douglas County. In the 1950's over
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Page 114 and 115: crusta I blocks. I t has been exten
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Schmela, R.J., and Palmer, L.A., 19
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Acknow ledgements This work is a re
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Components of a 1975 Chevrolet Capr
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PITTSBURG BLUFF FOSSILS DESCRIBED "
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28 December 1972 19 January 1973 .-
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Figure 4. View of both houses of Fi
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-.-, • Figure 6. logs had been sa
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Figure 8. Irregular shorel ine of b
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29 October 1973 10 June 1975 Figure
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In 1875 the width of the spit, C, w
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Volume 38, No.9 September 1976 STAT
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(often minute) to medium vessels, t
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(above) in its increased dorso-vent
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MINERAL SYMPOSIUM ANNOUNCED The Pac
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KEEP IN TOUCH! Of course you notify
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" " " EASY GIVING" " " ORE BIN READ
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TREASURES FROM OLD ORE BINS 25¢ pe
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450 ___ -+---+-________ --+ _____ 4
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BLM ISSUES OIL AND GAS LEASES IN WE
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The Ore Bin Published Monthly By ST
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that some flows, such as the Roza B
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w I I I I 30 60 N . - .t. ..! + S N
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VOLlfIE 38, I'I:J, 12 DeCEMBER 1976
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Ancient terraces: Ancient elevated
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00 00 A u o EJ EXPLANATION Beach sa
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DESCHUTES COUNTY BULLETIN PUBLISHED
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The Ore Bin - Oregon Department of Geology and Mineral Industries

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