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USGS MF-2336, Explanation

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USGS MF-2336, Explanation U.S. DEPARTMENT OF THE INTERIOR CORRELATION OF MAP UNITS MISCELLANEOUS FIELD STUDIES MF-2336 U.S. GEOLOGICAL SURVEY SHEET 5 OF 6, Version 1.0 QUATERNARY AND TERTIARY Pamphlet accompanies map COAST RANGES PROVINCE OVERLAP DEPOSITS DESCRIPTION OF MAP UNITS The Yager terrane locally includes: ecsp Serpentinite melange-Scarce blocks up to 500 m long, of basalt, Ycgl Conglomerate-Polymict, well rounded, consisting largely of recycled diabase, gabbro, and ophiolitic breccia in a sheared matrix of serpentinized Holocene 125¡ Qt Qls 41¡ QUATERNARY AND TERTIARY OVERLAP DEPOSITS clasts. Clasts commonly include abundant hypabyssal volcanic and plutonic dunite and minor harzburgite; locally may include small intrusive bodies of FRANCISCAN COMPLEX Qal 124¡ rocks of granitic to dioritic composition; and less common metaclastic rocks diorite and quartz diorite. At Red Lassic, northeast of Zenia (Sheet 3), Qm MAD RIVER Figure 3. Generalized map showing principal faults and folds discussed in the map area, (including black or green radiolarian chert, quartzite, metasandstone and includes a large block of pillow basalt flows and flow breccia with area of active Mendocino uplift (stippled pattern), and major plates. Map units delineated Qal Alluvial deposits (Holocene and late Pleistocene?)-Clay, silt, sand, gravel, Pleistocene QUATERNARY metaconglomerate) interleaved chert having Upper Jurassic (Tithonian) radiolarian assemblage locally for purposes of location include: Neogene overlap deposits (QTw), Coast Ranges and boulders, deposited in stream beds, alluvial fans, terraces, flood plains Coastal Belt QTog (cr), King Range (kr), Yager terrane (y), False Cape terrane (fc), Central belt (cb), Yolla Central belt (table 1 and fig. 3, Loc. 79; Kaplan, 1983; 1984). Elsewhere, chert and ponds; and soils formed on these deposits. Includes largely Holocene Bolly terrane (yb), Pickett Peak terrane (pp); western Klamath terrane (wkt), Smith River Melange of the Central belt (early Tertiary to Late Cretaceous)- associated with blocks in serpentinite melange are Late Jurassic (late Coastal terrane Fi ck FAULT subterrane (srs), Rattlesnake Creek terrane (rct), Western Hayfork terrane (wht), and deposits in modern stream channels and on flood plains l QTw e Consists of a matrix of clayey, penetratively sheared argillite and fine-grained Tithonian to Kimmeridgean) in age (McLaughlin and others, 1988) Pliocene H Eastern Hayfork terrane (eht). Faults that are not labelled are keyed to numbers on map: i Arcata l Undeformed marine shoreline and aolian deposits (Holocene and late l Qm C sandstone, locally with intercalated green tuff and hard elliptical carbonate Ridge 1a. Northern Little Salmon fault zone. 1b. Southern Little Salmon fault zone. 2a. Pleistocene)-Gravel and sand deposited in marine terraces, on benches, and co1 co2 co3 co4 A NORTH AMERICAN Granite concretions armored with scaly black argillite. Includes blocks up to several Del Puerto(?) terrane King Range Butte Northern Bear River fault zone. 2 b. Southern Bear River fault zone. Faults associated on dunes along present shorelines. In northern Eureka quadrangle, near S ZONE kilometers across, of diverse lithologies and ages. Age range of the Central Rocks of the Del Puerto(?) terrane-Exposed locally along western margin of terrane Upper with Pacific-North American plate transform boundary are numbered: 3. North Fork C F Arcata, includes older late Pleistocene dune sands (Carver and others, 1984) ? ? ? ? R Road thrust zone. 4. Mattole Road Lineament. 5. Honeydew fault zone. 6. Whale E belt is based on the paleontologic and isotopic age range of rocks in the Central belt of Franciscan Complex east of Benbow (Sheet 3) and at Bear A PLATE Eureka S Qt Undifferentiated nonmarine terrace deposits (Holocene and Pleistocene)- H Gulch-Bear Harbor fault zone. 7. Fault associated with 1906 earthquake surface ruptures krk krk krk 1a. W melange and on inferred range in age of penetrative shearing, boudinage, and Buttes northwest of Garberville (Sheet 3). Rocks of this terrane are krc krl D Dissected and (or) uplifted gravel, sand, silt, and clay, deposited in fluvial False Cape Middle Miocene A at Pt. Delgada (Prentice and others, 1999). T related deformation that occurred during melange formation. Components of correlated with a more extensive ophiolite complex and overlying 1 2 3 terrane I E settings. In western Eureka quadrangle (Sheet 1) unit includes minor krb A R 1b. the Central belt melange include: sedimentary rocks with island arc affinities 300 km to southeast, in the Del GORDA PLATE F shallow marine intertongues and warped and tilted beds of late Pleistocene fc QTw A Lower 1b. U Unnamed Metasandstone and meta-argillite (Late Cretaceous to Puerto canyon area, northeast of San Jose, California (McLaughlin and L T Hookton and Rohnerville Formations of Ogle (1953), in addition to younger M Late Jurassic)-Arkosic lithic metasandstone and meta-argillite, others, 1988a). Includes: ? ? ? ? LI late Pleistocene and Holocene fluvial terrace units a few feet to a few tens of TT E LE A" cb reconstituted to textural zones 1 to 2A (Jayko and others, 1989) and dpms Mudstone (Late Jurassic)-Dark green to black, tuffaceous scaly S feet higher than normal modern high-water level G A LM C metamorphosed to pumpellyite and lawsonite grade, with less than 1/2 mudstone, highly sheared locally, containing carbonate concretions and O O TERTIARY A Landslide deposits (Holocene and Pleistocene)-Unsorted clay- to boulder- A N Qls Ti Oligocene F S percent K-feldspar (fig. 5). Unit locally includes cobble- to pebble-size nodules with radiolarian faunas of Late Jurassic (late Tithonian) age. A T U A size debris and broken rock masses that have moved downslope in debris T Yager terrane L L Present only locally above ophiolite east of Benbow (Sheet 3) T B polymict conglomerate or monomict chert-pebble conglomerate. Locally, H 1 0 1 234 5 10 15 flows, earth flows, and as more-or-less intact rotational or translational E MILE Z L ? ? ? FERNDALE FAULTO T the metasandstone and meta-argillite depositionally overlie radiolarian Coast Range ophiolite (Middle and Late Jurassic)-Dismembered R N 1 0 1 234 51015KILOMETER blocks, largely from Pleistocene to present. Only large landslides, occupying E y T U chert in composite melange blocks. In some places in blocks metasandstone ophiolite, consisting of: H tens to hundreds of acres, are depicted here. Gu R ST t h ek is imbricated or structurally interleaved with chert and basalt. Fossils from dpt Tuffaceous chert (Late Jurassic)-Dark-green to brownish-red, Eocene rie C re U co1 co2 co3 co4 krk krk krk 2a. False QTw S QTog Older alluvium (Pleistocene and (or) Pliocene)-Weakly consolidated to T unnamed metasandstone and meta-argillite range in age from Late Cretaceous tuffaceous radiolarian chert present locally east of Benbow (Sheet 3), below y1 y2 y3 Ycgl Cape 123¡ 2b. FAL unconsolidated alluvial sand and gravel in patches as much as 700 feet 1 2 3 40.5¡ S E R B" C US M 40.5¡ to Late Jurassic. Carbonate concretions and local, thin, silty, hemipelagic mudstone and above mafic extrusive and intrusive rocks. Contains Central Belt AP E S U eht fc FA higher than the present stream level; locally may be related to remnants of L WILSO U F E N A R G S chert beds and lenses in melange matrix contain radiolaria and dinoflagellates radiolarian assemblage of Late Jurassic (Kimmeridgean) age LT Bridgeville S P ? ? ? ULT I R A ? ? ? ? C D O old upland surfaces such as preserved along the upper reaches of Plummer, O O BEAR RIVER G L I dpb O G N Basaltic flows and keratophyric tuff (Jurassic?) FAULT E U wkt T ranging in age from Late Jurassic to Early Cretaceous (Tithonian to Aptian or -Uralitic and intruded T A A C Cape Mendocino A’ F T R Naufus, and Bear Wallow Creeks in the Pickett Peak area of the Garberville T S A N E H E H ZONE G U Albian). Some metasandstone and conglomerate in composite blocks locally by mylonitic quartz keratophyre dike rocks, present locally along west ? Paleocene a T cb K wht r F (srs) R Devil’s Gate b L A F quadrangle (Sheet 3). Also includes alluvium in upland basins to the west of er F MENDOCINO FRACTURE ZONE cr vill T AULT A U boundary of Central belt of Franciscan Complex near Benbow (Sheet 3) e L O U S depositionally overlie chert with a Late Cretaceous (Cenomanian) radiolarian An Z T t B O R L the Eastern belt of the Franciscan Complex, such as Hoaglin and Kettenpom PE if T TR o E K dpd Diabase (Jurassic?)-Dikes and sills, fine to coarse grained, with ophitic cwr OL G r N assemblage. The unnamed metasandstone and meta-argillite is divided into I m L A a E FA Valleys in the Zenia and Lake Mountain 1:24,000 quadrangles (Sheet 3) F rb T A e U ? T L subunits of melange and broken formation based principally on topographic texture, present below basalt flows near Benbow and forms Bear Buttes ? ? ? ? ? Petrolia UL rv T T i H B’ rct QTw Marine and nonmarine overlap deposits (late Pleistocene to middle 4. ll Black cols cob co1 co2 co3 co4 Krp 3. Z e R north of Garberville (Sheet 3). Lower part of diabase unit of Bear Buttes U Lassic expression in aerial photographs and outcrop data: GREAT VALLEY SEQUENCE AND O Bull Creek S Miocene)-Thin-bedded to massive, weakly lithified siltstone, fine- to N y S S E n Red U T P L Melange locally includes minor cumulate gabbro. Lower diabase contact considered f I P cm1 -Predominantly penetratively sheared, locally tuffaceous, scaly o cb Lassic N H Late r Devil’s Elbow medium-grained sandstone, silty to diatomaceous mudstone and locally soft, ? ? COAST RANGE OPHIOLITE SAN ANDREAS FAULT ZONE m E U meta-argillite and less abundant blocks of metasandstone.
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