U.S. Department of the Interior Scientific Investigations Map 3186 U.S. Geological Survey Sheet 2 of 2 Pamphlet and CD-ROM accompany map
CORRELATION OF MAP UNITS [Vertical arrows indicate age uncertainties of a few units; extended boxes indicate known age ranges for long-lived units. Stipple indicates units that are partly or wholly pyroclastic. See Description of Map Units (in pamphlet) for specific unit age assignments]
SURFICIAL DEPOSITS VOLCANIC ROCKS
South Sister and Vicinity acc
rdc′ rdc myc
i p pdf rrm
al 7.7 ka (age of Mazama ash) Holocene
Postglacial mec av ls bbr Early Holocene or mlc bcc bes latest Pleistocene Middle Sister and Vicinity bsl
dig msb
17-18 ka btk
dsw mss dhr dbh
dms g s
mms′ mmi mms mmt mmm 20 ka dsn North Sister and Vicinity
mtp mpn dnt dnt′ dlp mrg anh msc mmn mcl des awm awr awc mml dss dlg mps ahl dbl rsc mnt rsc′ awf adl asw awa ahi
mnh dcl
als aeg
dkb rct adh dwl drm
dmn alh alg dcn alc 30 ka
dgl dcg ahc apc
rgl ddl dpg Late Pleistocene rse rpg
dmw ahi
dml aph′ dgc asn aph dse rkb rdh ? r58
rsf QUATERNARY mhl mhd dwp rpc aef dlc
roc
rmc aoc mls mpm mlb mkm mnf asy 50 ka
rsw mwa mwy
mhr mfy mys
mey mns Broken Top and Vicinity myl
bwm myw 100 ka mst bss mmc
bbd Late or middle acp mbc msp ? rsg Pleistocene bwl bjc mth ? bac mth′ bnf ruc dmc mdl
mws msf mdw spt
mwh 200 ka abt mbt
bsb bhs
bsb′ bwy
awy mts Middle Pleistocene ?
? mbw
mtw dtl
mbl
rtl
mtb
LIST OF MAP UNITS mtp Basaltic andesite of Teardrop Pool (late Pleistocene) mss Basaltic andesite of Middle Sister summit (late Pleistocene) bwm Basalt west of Millican Crater (late Pleistocene) mtw Basaltic andesite of The Wife (middle Pleistocene) [Stipple indicates units that are partly or wholly pyroclastic. See Description of Map Units (in rct Rhyolite of South Sister climbers trail (late Pleistocene) roc Rhyolite of Obsidian Cliffs (late Pleistocene) dmc Dacite of Mesa Creek (middle Pleistocene) mwh Basaltic andesite of Whychus Creek (middle Pleistocene) pamphlet) for complete unit descriptions] rdc′ rdc Rhyolite of “Devils chain” (late Holocene) MAFIC PERIPHERY dse Dacite east of Sink Creek (late or middle Pleistocene) myc Basaltic andesite of Yapoah Crater (Holocene) SURFICIAL DEPOSITS rdh Rhyolite of Devils Hill (late Pleistocene) North Sister and Vicinity dtl Dacite of Todd Lake (middle Pleistocene) rtl Rhyodacite southwest of Todd Lake (middle Pleistocene) i Glacial ice (late Holocene) anh Andesite agglutinate north of Hayden Glacier (late Pleistocene) rgl Rhyolite of Green Lakes (late Pleistocene) mbc Basaltic andesite of Black Crater (late or middle Pleistocene) r58 Rhyolite of Dome 5803 (late Pleistocene) p Pumice deposits (late Holocene) asy Hornblende-bearing andesite southeast of Yapoah Crater (late Pleistocene) rkb Rhyolite of Kaleetan Butte (late Pleistocene) mbl Basaltic andesite of Bare Lake (middle Pleistocene) spt Shevlin Park Tuff (middle Pleistocene) pdf Pumiceous debris-flow deposits (late Holocene) awa Andesite west of upper Alder Creek (late Pleistocene) rmc Rhyolite of Mesa Creek (late Pleistocene) mdl Basaltic andesite north and south of Demaris Lake (middle Pleistocene) al Alluvium (Holocene) bac Basalt of Alder Creek (late or middle Pleistocene) EXPLANATION OF MAP SYMBOLS rpc Rhyolite of Park Creek (late Pleistocene) mdw Basaltic andesite west of Dutchman Flat (late or middle Pleistocene) g Glacial deposits, undivided (Holocene and late Pleistocene) Contact—Long-dashed where approximately located; short-dashed where inferred; bbd Basalt of Brush Draw (late or middle Pleistocene) rpg Rhyodacite of Prouty Glacier (late Pleistocene) mec Basaltic andesite and basalt of “Egan Cone” (early Holocene) dotted where concealed. Internal contacts in volcanic units indicate individual s Surficial deposits, undivided (Holocene and late Pleistocene) emplacement lobes; in surficial units, deposits of different depositional intervals mey Basaltic andesite east of Yapoah Lake (late Pleistocene) rrm Rhyolite of Rock Mesa (late Holocene) mhr Basaltic andesite of The House Rock (late Pleistocene) av Debris-avalanche deposit (Holocene or latest Pleistocene) Dikes rsc mfy Basaltic andesite of fissure vent south of Yapoah Lake (late Pleistocene) Rhyolite of Separation Creek (late Pleistocene) mkm Basaltic andesite of Koosah Mountain (late Pleistocene) ls Landslide deposit (Holocene or latest Pleistocene) rsc′ Moraine crests mml Basaltic andesite of South Matthieu Lake (late Pleistocene) rse Rhyolite southeast of Lewis Glacier (late Pleistocene) mlb Basaltic andesite of Little Brother (late Pleistocene) VOLCANIC ROCKS Little Ice Age mmn Basaltic andesite of North Matthieu Lake (late Pleistocene) rsf Rhyolite of South Fork Whychus Creek (late Pleistocene) mlc Basaltic andesite of Le Conte Crater (early Holocene or latest Pleistocene) Early Neoglacial SILICIC FOCUS mns Basaltic andesite of North Sister (late and middle Pleistocene) rsw Rhyolite southwest of Lewis Glacier (late Pleistocene) mmc Basaltic andesite of Millican Crater (late Pleistocene) South Sister and Vicinity Younger Dryas mnt Basaltic andesite north of Trout Creek (late Pleistocene) adh Andesite dome of Lewis Glacier headwall (late Pleistocene) Middle Sister and Vicinity mpm Basaltic andesite of Park Meadow (late or middle Pleistocene) Last Glacial Maximum mpn Basaltic andesite north of Scott Pass (late Pleistocene) aeg Andesite of Eugene Glacier (late Pleistocene) adl Andesite of Demaris Lake (late Pleistocene) msb Basaltic andesite of Sims Butte (latest Pleistocene) Ejecta rim mps Basaltic andesite south of Scott Pass (late Pleistocene) ahc Andesite tephra fall of Hodge Crest (late Pleistocene) aef Andesite tephra fall at base of east face of Middle Sister (late Pleistocene) msc Basaltic andesite of Separation Creek (late Pleistocene) Lava-levee crest mst Basaltic andesite south of Trout Creek (late or middle Pleistocene) ahi ahl Andesite of headwaters of Linton Creek (late Pleistocene) msf Basaltic andesite of South Fork Whychus Creek (middle Pleistocene) ahi Andesite intrusive complex of Hodge Crest (late Pleistocene) Lava-flow direction mwa Basaltic andesite west of upper Alder Creek (late Pleistocene) 20 alg Andesite west of Lost Creek Glacier (late Pleistocene) alc Andesite of Linton Creek (late Pleistocene) msp Basaltic andesite of Soap Creek–North Fork Whychus Creek confluence (late or Strike and dip of ejecta and stacks of thin lava flows mwy Basaltic andesite scoria cone west of Yapoah Lake (late Pleistocene) middle Pleistocene) alh Andesite of Lewis Glacier headwall (late Pleistocene) aoc Andesite of Obsidian Creek (late Pleistocene) mtb Basaltic andesite and basalt of Trout Creek Butte (middle Pleistocene) Volcanic craters and partial crater rims—Hachures point inward myl Basaltic andesite of Yapoah Lake (late Pleistocene) als Andesite south of Lewis Glacier (late Pleistocene) asw Andesite of southwest slope of Middle Sister (late Pleistocene) mth mth′ Basaltic andesite of The Husband (middle Pleistocene) Volcanic vent (other than craters and fissures) mys Basaltic andesite southwest of Yapoah Lake (late Pleistocene) apc Andesite of Park Creek (late Pleistocene) awc Andesite west of Collier Glacier (late Pleistocene) mts Basaltic andesite southeast of “Todd Creek” (middle Pleistocene) Volcanic fissure vent myw Basaltic andesite window west of Yapoah Lake (late or middle Pleistocene) aph Andesite of Prouty Glacier headwall (late Pleistocene) awm Andesite west of Middle Sister (late Pleistocene) Broken Top and Vicinity aph′ Andesite tephra fall near base of Prouty Glacier headwall (late Pleistocene) awr Andesite west of Renfrew Glacier (late Pleistocene) abt Andesite and dacite of Broken Top (middle Pleistocene) asn Andesite south of Newberry flow (late Pleistocene) dbh Dacite of “Black Hump” (late Pleistocene) awy Andesite of Whychus Creek (middle Pleistocene) SOUTH NORTH awf Andesite of West Fork Park Creek (late Pleistocene) dhr Dacite of Hayden Glacier–Renfrew Glacier col (late Pleistocene) bwy Basalt of Whychus Creek (middle Pleistocene) dbl Dacite breccia of Lewis Glacier headwall (late Pleistocene) dig Dacite of Irving Glacier (latest Pleistocene) mbt Basaltic andesite of Broken Top (middle Pleistocene) South Sister dcg Dacite southwest of Clark Glacier (late Pleistocene) dlc Dacite of Linton Creek (late Pleistocene) Middle Sister North Sister mbw Basalt of Whychus Creek bridge (middle Pleistocene) “Black Hump” dcl Dacite of Chambers Lakes (late Pleistocene) dlp Dacite of Lane Plateau (late Pleistocene) mws Basaltic andesite west of Snow Creek (middle Pleistocene) Black Crater dcn Dacite north of Carver Lake (late Pleistocene) dms Dacite of Middle Sister summit (late Pleistocene) rsg Rhyodacite southwest of Golden Lake (late or middle Pleistocene) ddl Dacite of Dew Lake (late Pleistocene) dsn Dacite north of Separation Creek (late Pleistocene) ruc Rhyodacite of Upper Chush Falls (middle Pleistocene) dss Dacite of Sister Spring (late Pleistocene) des Dacite ejecta of South Sister summit (late Pleistocene) Peripheral Centers and Other Lavas dgc Dacite of Goose Creek (late Pleistocene) dsw Dacite domes southwest of Middle Sister (late Pleistocene) acc Andesite of Collier Cone (Holocene)
dgl Dacite of Green Lakes (late Pleistocene) mcl Basaltic andesite of Camp Lake (late Pleistocene) acp Andesite of Pole Creek scoria cone (late or middle Pleistocene)
dkb Dacite of Kokostick Butte (late Pleistocene) mhd Basaltic andesite of Hayden Glacier–Diller Glacier cleaver (late Pleistocene) bbr Basalt of Sparks Lake boat ramp (early Holocene or latest Pleistocene)
mhl Basaltic andesite of headwaters of Linton Creek (late Pleistocene) dlg Dacite of Lewis Glacier headwall (late Pleistocene) bcc Basalt of Cayuse Crater (early Holocene or latest Pleistocene) Broken Top dml Dacite southeast of Moraine Lake (late Pleistocene) mls Basaltic andesite of Linton Spring (late or middle Pleistocene) bes Basalt east of Sparks Lake (early Holocene or latest Pleistocene) lava flows
dmn Dacite north of Moraine Lake (late Pleistocene) mmi Basaltic andesite intrusion of Middle Sister (late Pleistocene) bhs Basalt south of The Husband (middle Pleistocene) Green Lakes Newberry flow dmw Dacite coulee west of Moraine Lake (late Pleistocene) mmm Basaltic andesite of Montague Memorial (late Pleistocene) bjc Basalt of James Creek (middle Pleistocene)
dnt Dacite north of Teardrop Pool (late Pleistocene) mms Basaltic andesite of Middle Sister (late Pleistocene) bnf Basalt of North Fork Whychus Creek (middle Pleistocene)
dnt′ Silicic dacite north of Teardrop Pool (late Pleistocene) mms′ Pyroxene-bearing variant of the basaltic andesite of Middle Sister (late bsb bsb′ Basalt of Sphinx Butte (middle Pleistocene) Pleistocene) dpg Dacite pumice fall of Prouty Glacier headwall (late Pleistocene) mmt Basaltic andesite tuff of Middle Sister (late Pleistocene) bsl Basalt southeast of Sparks Lake (early Holocene or latest Pleistocene)
drm Dacite of Red Meadow (late Pleistocene) mnf Basaltic andesite of North Fork Whychus Creek (late Pleistocene) bss Basalt of Spruce Spring (late Pleistocene)
dwl Dacite west of Lost Creek Glacier (late Pleistocene) mnh Basaltic andesite north of Hayden Glacier (late Pleistocene) btk Basalt and basaltic andesite of Talapus and Katsuk Buttes (latest Pleistocene)
dwp Dacite of Wickiup Plain (late Pleistocene) mrg Basaltic andesite of Renfrew Glacier (late Pleistocene) bwl Basalt of lower Whychus Creek (late or middle Pleistocene) Three Sisters volcanic chain forms 20-km-long reach along crest of the Cascade Range. Aerial view northward along east side of edifices. Photograph by Don Graham, helicopter pilot.
Geologic Map of Three Sisters Volcanic Cluster, Cascade Range, Oregon Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, By Denver, CO 80225, 1–888–ASK–USGS Digital files available at http://pubs.usgs.gov/sim/3186/ Suggested citation: Hildreth, Wes, Fierstein, Judy, and Calvert, Andrew T., 2012, Geologic By Wes Hildreth, Judy Fierstein, and Andrew T. Calvert map of Three Sisters volcanic cluster, Cascade Range, Oregon: U.S. Geological Survey Scientific Investigations Map 3186, pamphlet 107 p., 2 sheets, scale 1:24,000. (Available at 2012 Printed on recycled paper http://pubs.usgs.gov/sim/3186/.)