GEOLOGIC MAP OF THE 3.72 Ma HANNEGAN CALDERA AND ASSOCIATED ROCKS NORTH CASCADES, WASHINGTON, USA

LEGEND AND ROCK UNITS

QUATERNARY o 121o37'30" 121 30' Silesia Creek Ql landslide glacier

Copper Mtn TERTIARY A Lookout PLIOCENE 1865 Tcp Granite Mtn CRF Chilliwack River Fault Tcp cb 2039 Post-collapse magmatic units mm dikes, undifferentiated cb Egg Tcbrp acp: Andesite lava of Chilliwack 10 Tcgp Lake Pass mm u Tcnm: Granite and quartz Hannegan Pk HC 113 monzonite of Nooksack Ruth Creek Cirque rhg Tcid: Quartz diorite and quartz MB 380 Copper Creek monzonite of Icy Peak mm 5 Intrusive pods and domes: c CRF Tcp Hells Gorge rdr: Rhyodacite of Ruth Mt; Tcbrp 30 v rhg: Rhyolite of Hell's Gorge Hannegan acd: Andesite of Cassiope dome Pass Ths 48 1681 Thh Ql Chilliwack River CRF HC 65 Thr: Ignimbrite of Ruth Mountain Kes acd Cassiope Dome (Pt. 5930) 915 Ths: intracaldera sedimentary Creek rocks 48o52'30" 41 Caldera Thh: Ignimbrite of Hannegan Peak Kes Ths Intraignimbrite monolithologic breccia 2010 v 35 5 Chilliwack mm schist facies HC 88 Pass Tcbrp cb Chillwack batholith rocks mm v pre-caldera volcanic rocks acp ice u undifferentiated rocks Ruth Mtn 1880 Chilliwack composite batholith plutons Tcrg Mineral Mtn with contacts as per Tabor et al., 2003 (no pattern): rdr Thr Nooksack River Tcbr Tcp, Pocket peak phase (Olig.) Tcbrp, Price Gl. pluton (age?) HC 123 Tcbr, Baker R. phasev (Olig) Pluton Tcrgd, Ruth Ck pluton (Mio.)

Pass Creek Tcrg, Granite of Ruth Mt (Plio?) Tcid Creek Tcgp, Granite porph. of Egg Lk (Plio) HC 124 MESOZOIC

Ked: schist facies of Darrington Tcnm Phyllite member of Shuksan ice Metamorphic Suite 2152 N Icy Peak 2156 Phantom Pass o 48 50' 10 contact, dashed where inferred NooksackTcnm Cirque Tcbr 41 strike and dip of bedding or flow Crystal Creek Kes ice 5 foliation KILOMETERS fault; ball on downthrown block 2268 0 1 2 3 Kes Contour interval: 200 ft = 61 m Seahpo Peak A' dated samples with number. See text

David S. Tucker Geology Department Western Washington University 2006 Bellingham, Washington, USA

Published by Tucker, D.S., 2006, Geologic map of the 3.72 Ma Hannegan The Geological Society of America, Inc. Caldera and Associated Rocks, North Cascades, Washington: 3300 Penrose Place, P.O. Box 9140 Geological Society of America Digital Map and Chart Series 3, Boulder, Colorado 80301-9140 2 sheets, scale: 1:24,000, © 2006 The Geological Society of America doi: 10.1130/2006.DMCH003. Printed in the U.S.A.