Geology of the Freshwater Bay Area Chichagof Island, Alaska
By ROBERT A. LONEY, WILLIAM H. CONDON, and J. THOMAS DUTRO, JR, MINERAL RESOURCES OF ALASKA
GEOLOGICAL SURVEY- BULLETIN 1108-C
General geology of an area underlain largely by middle Paleozoic rocks, with emphasis on stratigraphy, structure, and petrography
UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963 UNITED STATES DEPARTMENT OF THE INTERIOR
STEWART L. UDALL, Secretary
GEOLOGICAL SURVEY
Thomas B. Nolan, Director
For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS
Page Abstract______...______._____-__---___--__.------_-____---__ Cl Introduction.....______2 Previous investigations.______4 Purpose and scdpe__.______--_-___---___---_--__-______- 5 Bedded rocks______-_-_-______-_-_-_._____.______6 i Silurian (?) or Devonian (?) rocks.______6 Unnamed argillite and graywacke__.______-__-_._--____ 6 Distribution and topographic expression.______6 Stratigraphy and petrography ______8 False Bay area_-_------__--_------__-_- 8 Southwest of Freshwater Bay____---_---_-______- 11 , Conglomerate at East Point______12 Age and correlation______-_-_-_-_-_-_-_--______13 ' Devonian rocks.______13 Kennel Creek limestone.------.---- 13 Distribution and topographic expression.______13 Stratigraphy. ______14 Age and correlation____-____-_-_-_-_-_-___-_-______16 Cedar Cove formation______17 Distribution and topographic expression______17 Stratigraphy and petrography ______18 Age and correlation____-_-----_--_-_---_-_--______-_-__ 22 Freshwater Bay formation______23 Distribution and topographic expression______23 ' Stratigraphy and petrography------..------.-__--.._._ 23 Southwest limb of Freshwater Bay syncline______24 Lower greenstone member....______24 Middle rhyolitic member______25 Upper andesitic member.______28 Northeast limb of Freshwater Bay syncline______29 Age and correlation.____-_--_-____._---______31 Mississippian rocks__.______32 lyoukeen formation______-----_--_-._-_-__--______---__ 32 Distribution and topographic expression.______32 Stratigraphy and petrography.______32 Gypsum deposits___-__-_-_-_-___-_-_-_.____._._____ 34 Measured sections______34 Age and correlation____---_--_--__._-_-_--______-___ 36 j Quaternary deposits..___-______--_-----___-_--______-______37 in IV CONTENTS