U.S.G.S. OFR 95-20 U.S.G.S. OFR 95-20 U.S. DEPARTMENT OF THE INTERIOR U.S. GEOLOGICAL SURVEY

Reconnaissance Geologic Map of the Lane Mountain 7.5' Quadrangle, Oregon

U. S. Geological Survey Open-file Report 95-20 A. S. Jayko

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, product or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Menlo Park, California 1996 Reconnaissance geologic map of the Lane Mountain 7.5* Quadrangle flow deposits considered to be either arc basin and/or post-orogenic flysh basins that were A. S. Jayko 1995 syntectonic with the waning phases of arc collapse (Imlay, et al., 1959, Ryberg, 1984, Introduction Garcia, 1982, Roure andBlanchet, 1983). The The Lane Mountain 7.5 minute quadrangle intermediate and mafic igneous rocks of the is situated at the junction of three major Rogue arc and the pre-Nevadan sedimentary geologic and tectonic provinces the cover (the Galice Formation, (Garcia, 1979)) are northernmost Klamath Mountains, the intruded by siliceous and intermediate plutonic southeastern part of the Oregon Coast Ranges rocks principally of quartz diorite and and western part of the Cascade Range (Figure granodiorite composition (Dott, 1965, Saleeby, 1). Rocks of the Klamath Mountains province et al., 1982, Garcia, 1982, Harper and Wright, that lie within the study area include ultramafic, 1984). The plutonic rocks are locally tectonized mafic, intermediate and siliceous igneous types into amphibolite, gneiss, banded gneiss and (Diller, 1898, Ramp, 1972, Ryberg, 1984). augen gneiss. Similar metamorphic rocks have Similar rock associations that lie to the yielded metamorphic ages of 165 to 150 Ma southwest yield Late Jurassic and earliest (Coleman, 1972, Hotz, 1971, Saleeby, et al., Cretaceous radiometric ages (Dott, 1965, 1982, Coleman and Lanphere, 1991) Saleeby, et al., 1982, Hotz, 1971, Harper and The Jurassic arc rocks and sedimentary Wright, 1984). These rocks, which are part of cover occur as a tectonic outlier in this region the Western Klamath terrane (Western Jurassic (Figure 2) as they are bound to the northwest belt of (Irwin, 1964), are considered to have and southeast by melange, broken formation and formed within an extensive volcanic arc and semi-schists of the Dothan Formation and rifted arc complex (Harper and Wright, 1984) Dothan Formation(?) that are considered part of that lay along western North America during the a Late Mesozoic accretion complex (Ramp, Late Jurassic (Garcia, 1979, Garcia, 1982, 1972, Blake, etal., 1985) The plutonism that Saleeby, et al., 1982, Ryberg, 1984). Imbricate accompanied arc formation and tectonic thrust faulting and collapse of the arc during the collapse of the arc does not intrude the Nevadan orogeny, which ranged in age between structurally underlying Dothan Formation, about 150 to 145 Ma in the Klamath region indicating major fault displacements since the (Coleman, 1972, Saleeby, et al., 1982, Harper early Cretaceous. Semischistose and schistose and Wright, 1984) was syntectonic with, or rocks of the accretion complex have yielded closely followed by deposition of the volcano- metamorphic ages of around 125-140 Ma where lithic clastic rocks of the Myrtle Group. The they have been studied to the southwest Myrtle Group consists of Late Jurassic and (Coleman and Lanphere, 1971, Dott, 1965, Early to middle Cretaceous turbidity and mass Coleman, 1972). These rocks were unroofed

1 and unconformably overlain by marine deposits flow tuff. The section is gently east-tilted and is by late Early Eocene time (Baldwin, 1974). slightly disrupted by NE trending faults with The early Tertiary history of this region is apparent normal separation. controversial. The most recent interpretation is that during the Paleocene and early Eocene the Previous Work convergent margin was undergoing transtension The first major geologic study of the or forearc extension as suggested by the Roseburg and adjacent areas was carried out by voluminous extrusion of pillow basalt and Diller (1898) and Wells and Peck (1961) who related dike complexes (Wells, et al., 1984, mapped the basic geologic framework of the Snavely, 1987). This episode was followed region. More detailed mapping relevant to this shortly by thrust and strike-slip faulting in the map area was carried out through a concerted late early Eocene (Ryberg, 1984). effort at University of Oregon, Eugene under the During the Eocene, the Mesozoic direction of E.M. Baldwin that resulted in the convergent margin association of arc, clastic completion of three Masters theses (Hixson, basin, and accretion complex was partly 1965, Champ, 1969, Seeley, 1974) which helped unroofed and faulted against early Cenozoic refine major unit boundaries (See index to rocks of the Oregon Coast Ranges (Ramp, 1972, geologic mapping). The map area included in Baldwin, 1974, Champ, 1969, Ryberg, 1984). the regional compilation of Douglas County by Faults that are typical of this period of Ramp and Beaulieu (Ramp, 1972) was primarily deformation include high-angle reverse faults generalized from Diller (1898). Ryberg (1984) with a very strong component of strike-slip and Niem and Niem (1990) provided major displacement characterized by the low-angle regional tectonic syntheses concerning the rake of striae. Thrust and oblique-slip faults are evolution of early Tertiary sedimentary rocks of ubiquitous in early Tertiary rocks to the the region. northwest (Ryberg, 1984, Niem and Niem, This study was undertaken as part of a 1990). contribution to 1:100,000 mapping of the The late Mesozoic and early Cenozoic arc Roseburg 30' x 60' quadrangle. Field studies and forearc rocks are unconformably overlain were made during the middle summer months of by the Late Eocene and younger, mainly 1992 and 1993. The mapping was greatly continental fluvial deposits and pyroclastic facilitated by the numerous logging roads that flows of the Cascade arc (Peck, et al., 1964, lace the national forests lands, otherwise heavy Baldwin, 1974, Walker and MacLeod, 1991). vegetation and deep weathering of the region Minor fossiliferous shallow marine sandstone is would have limited access to rock exposure. locally present. The volcanic sequence consists There are several important modifications of a homoclinal section of about 1 to 2 to the regional mapping (Walker and MacLeod, kilometers of andesitic to rhyolitic flows and ash 1991) that have resulted from this investigation. The nature of the contact relations between the sequence; the melange, broken formation and major units within Klamath lithologies has been semi-schists of the Late Mesozoic accretion investigated in greater detail and were found to complex represented by the Dothan Formation; be dominantly major fault zones, and commonly the Paleocene and early Eocene forearc basin normal faults. The sense of displacement on the deposits; and lastly, the Late Eocene to major bounding structures was given careful Miocene? rocks of the western Cascade volcanic attention. Many high-angle normal faults cut arc. low-angle thrust faults that are interpreted as The Rogue arc complex consists of an Nevadan in age. There were no depositional igneous complex that includes predominantly contacts between Myrtle Group rocks and hornblende gabbro, hornblende diorite, and plutonic rocks evident in the field, likewise the diabase rocks that are commonly slightly to abundant conglomerates of the Myrtle Group strongly foliated. The extrusive part of the were devoid of intermediate plutonic clasts. complex is characterized by quartz keratophyre, Similarly the contacts between Rogue volcanic keratophyre, plagioclase porphyry flows, and hypabyssal rocks were characterized by pillows, hypabyssal dikes and flows, flow semi-ductile to cataclastic fabrics of low breccia, and minor tuffaceous sedimentary rock. greenschist facies that were generally devoid of These rocks are commonly tectonically silicification, siliceous veins or aplitic dikes brecciated and have undergone low to moderate suggesting the contacts are faults and the faults greenschist facies metamorphism. They are were post-plutonic. The major structural locally intruded by quartz diorite, granodiorite boundary between the Rogue arc complex and and similar siliceous plutonic rocks that are structurally underlying rocks includes a variety generally unfoliated or weakly foliated near the of ductile high strain rocks, schists and semi- margins. Metamorphosed country rock that was schists that occur within a kilometer or two wide gabbroic to intermediate in composition is zone that is low-angle, east-dipping and west- locally preserved; however, along many verging. contacts the primary intrusive contact between the 'older arc' and younger siliceous plutonic Stratigraphy rock is obscured by faults that are interpreted as The rocks of the area can be separated into low-angle normal faults. four major sequences that are characteristic of The Rogue arc complex is unconformably the tectonic provinces they represent. From overlain by unmetamorphosed clastic rocks of oldest to youngest, as described above are the the Myrtle Group which includes the Riddle and Late Jurassic Rogue arc complex including a Days Creek Formations that in this area range in younger plutonic complex, an age from lowest Cretaceous (Berriasian) to Late unmetamorphosed cover sequence that is Albian. The basal part of the section includes stratigraphically equivalent to the Great Valley tuffaceous sedimentary rocks and volcanic breccia suggesting that deposition was in part clastic rocks at the base of the section generally coeval with arc volcanism. Conglomerates in fine towards the north. In the southeastern part the lower part of the section are rich in mafic to of the map area, the basal section is intermediate volcanic clasts and dark chert or characterized by cobble conglomerate, whereas cherty tuff, and lack any significant component to the north it consists of fine-grained sandstone, of plutonic rock. In contrast, plutonic clasts are siltstone and shale. The unit also generally quite abundant in conglomerate within the basal becomes finer-grained up section. The Colestin Tertiary section in the quadrangle. is overlain by a regionally extensive, generally In the Lane Mountain quadrangle there are chaotic unit that is olisostromal and lahar-like in only thin fault slivers of metagraywacke which character with abundant blocks of andesitic are continuous with the more regionally volcanic rock as well as disrupted and slumped extensive belt of Dothan Formation. The sedimentary rock. This unit heralds the arrival Dothan Formation is considered to be part of a of voluminous andesitic and dacitic flows and subduction-accretion complex that formed breccias that are followed by several cooling during latest Jurassic and Cretaceous time units of rhyolitic, moderately welded ash flow (Ryberg, 1984, Blake, et al., 1985). tuff making up approximately half of kilometer Sedimentary rocks of the Oregon Coast of section. The rhyolitic ash flow tuffs are Ranges are represented by exposures of the locally capped by a pyroxene-phyric andesite. Eocene White Tail Ridge Formation (Ryu, et al., The volcanic units have previously been 1992) that are present in the northwest corner of mapped as part of the Oligocene Little Butte the quadrangle. The White Tail Ridge Volcanic Series (Peck, et al., 1964, Ramp, Formation consists of shallow marine, cross- 1972). bedded and massive planar bedded, fossiliferous Generally northwest trending basaltic to sandstone and mudstone. These rocks are part andesitic dikes can be found cutting the of a regionally extensive sequence of submarine Mesozoic plutonic rocks and well as the fan to nonmarine fluvial deposits that ranges Cenozoic rocks up through the rhyolite unit 1. from Paleocene to middle Eocene age (Ramp, Such dikes could range in age form Eocene to 1972, Baldwin, 1974, Ryberg, 1984, Niem and Miocene, however are generally considered to Niem, 1990, Ryu, et al., 1992). These rocks are be of Oligocene age in this area (Walker and considered to have been deposited in a forearc MacLeod, 1991). basin setting during the early Tertiary. Rocks of the western Cascade Province Structure consist of a basal sedimentary unit, the Colestin The structural grain of the region, as well as Formation of (Peck, et al., 1964, Baldwin, this quadrangle, is strongly dominated by north 1974), that represents a transition between 30 to 40 east trending faults and lithologic belts. shallow marine and fluvial conditions. The The faults represent upper- and middle-crustal brittle structures including high-angle reverse In the NW part of the Lane Mountain faults and associated overturned folds; deeper- quadrangle, a major northeast trending zone of seated north-west verging brittle and ductile imbricate thrust faults emplaces the Rogue arc shear zones within the plutonic complex; and complex and associated rocks over the Dothan high-angle faults with apparent normal complex. The igneous complex is locally separation that drop unmetamorphosed rock of overturned and in the adjacent quadrangle to the the Mesozoic forearc basin, as well as the west is pentratively deformed into strongly Tertiary Cascade arc rocks down against the banded and foliated gneiss, augen gneiss and plutonic complex. Many of the low-angle mylonitic rock along major northwest verging contacts between the Rogue arc complex and thrust faults. underlying plutonic rocks are interpreted as low- angle normal faults. The contact between rocks of the Jurassic Rogue arc complex and the underlying siliceous Metamorphism plutonic rocks is typically characterized by a Regional, contact, and hydrothermal broad zone of cataclastic deformation, the metamorphic rocks are present within the study hanging wall and foot-wall rocks are commonly area. Regional metamorphic rocks include low strongly foliated as well. Mineralization to moderate-grade greenschist facies rocks of associated with this deformation is typically of the arc complex that are inferred to have formed the lower greenschist facies with abundant during the Nevadan orogeny of Late Jurassic secondary epidote, albite and pumpellyite. age. Metamorphic rocks that formed during this These faults and breccias zones are not invaded event; which represents imbrication of the Late by magmatic fluids suggesting they are not Jurassic arc, include gneiss, banded gneiss, syntectonic with the plutonism but were augen gneiss and mylonitic rocks that are subsequent. The structural pendants of Rogue inferred to have originated at middle crustal arc are locally strongly hydrothermally altered. levels (Champ, 1969, Hotz, 1971, Garcia, 1982, Leaching of the mafic phases is common, Coleman and Lanphere, 1991). These rocks are particularly adjacent to the high-angle normal typically upper greenschist and lower faults. The high-angle normal faults are locally amphibolite facies. characterized by broad breccia zones and more Retrograde assemblages with epidote- rarely by intrusion of Tertiary andesitic and pumpellyite and lower greenschist facies basaltic dike rocks. Siliceous quartz diorite assemblages are commonly associated with dikes are found locally within the extrusive and cataclastic fabrics particularly near the major intrusive parts of the Rogue complex. Such dike fault contacts which bound the arc complex rocks have not been observed in the overlying units. This post plutonic semi-brittle Mesozoic sedimentary rocks. deformation may be post-Nevadan and Cretaceous in age. The cataclastic fabrics are stratigraphic terranes of southwest Oregon: inferred to have formed during extension Circum-Pacific Council for Energy and associated with uplift and unroofing of the Mineral Resources, Earth Science Series, v. plutonic rocks. l,p. 159-172. In addition, low-grade schists and semi- Champ, J. G., 1969, Geology of the northern schists of prehnite-pumpellyite facies are part of the Dixonville quadrangle, Oregon: characteristic of the higher-grade accretion University of Oregon, Eugene [M.Sc.], 86 complex rocks of the Dothan Formation in this P- area. These rocks generally structurally underlie Coleman, R. G., 1972, The Colebrooke Schist of major thrust faults that have the Rogue arc southwestern Oregon and its relation to the complex in the hanging wall. Schists of the tectonic evolution of the region: U.S. Dothan Formation are generally partially Geological Survey Bulletin 1339 61 p. reconstituted meta-sedimentary rocks with a Coleman, R. G., and Lanphere, M., 1991, The moderately developed pressure solution fabric Briggs Creek Amphibolite, Klamath and incipient development of chlorite, white Mountains, Oregon: it's origin and mica, ±_pumpellyite. Detrital tourmaline, dispersal: New Zealand Journal of Geology epidote, biotite, muscovite, hornblende and and Geophysics, v. 34, p. 271-284. pyroxene common constituents are common Coleman, R. G., and Lanphere, M. A., 1971, constituents of these rocks, but are not Distribution and age of high-grade indicative of the metamorphic grade. blueschists, associated eclogites and Hornfelsic hornblende gabbro rocks are amphibolites from Oregon and California: locally present near the margins of large quartz Geological Society of America Bulletin, v. diorite and granodiorite plutons. Hornfelsic 82, p. 2397-2412. rocks were also locally developed in Mesozoic Diller, J. S., 1898, Roseburg folio: Geological country rock near one of the larger Tertiary dike Atlas of the United States Folio No. 49, 20 intrusions. Hydrothermal alteration is P- widespread near high-angle faults that cut the Dott, R. H., 1965, Mesozoic-Cenozoic tectonic Rogue volcanic rocks. history of the southern Oregon Coast in relation to Cordilleran orogenesis: Journal References of Geophysical Research, v. 70, p. 4687- Baldwin, E. M., 1974, Eocene Stratigraphy of 4707. southwestern Oregon: Oregon Department Garcia, M. O., 1979, Petrology of the Rogue and of Geology and Mineral Resources Bulletin Galice Formations, Klamath Mountains, 83,40 p. Oregon: Identification of a Jurassic Island Blake, M. C, D.C. Engebretson, Jayko, A. S., Arc sequence: Journal of Geology, v. 86, p. and Jones, D. L., 1985, Tectono- 29-41. Garcia, M. O., 1982, Petrology of the Rogue western Cascade Range in Oregon: U.S. River island arc complex, southwest Geological Survey Professional Paper 449 Oregon: American Journal of Science, v. 449, 56 p. 282, p. 783-807. Ramp, L., 1972, Geology and Mineral Harper, G. D., and Wright, J. E., 1984, Middle Resources of Douglas County, Oregon: to Late Jurassic tectonic evolution of the Oregon Department of Geology and Klamath Mountains, California-Oregon: Mineral Industries Bulletin 75, 106 p. Tectonics, v. 3, p. 759-772. Roure, F., and Blanchet, R., 1983, A geologic Hixson, H. C., 1965, Geology of the southwest transect between the Klamath Mountains quarter of the Dixonville quadrangle, and the Pacific Ocean, southwestern Oregon: University of Oregon, Eugene Oregon: a model for paleosubduction: [M.Sc.], 97 p. Tectonophysics, v. 91, p. 53-71. Hotz, P. E., 1971, Plutonic rocks of the Klamath Ryberg, P. T., 1984, Sedimentation, structure Mountains, California and Oregon: U.S. and tectonics of the Umpqua Group Geological Survey Professional Paper 684- (Paleocene to early Eocene), southwestern B 1-20 p. Oregon: University of Arizona [Ph.D.], 280 Imlay, R. W., Dole, H. M., Wells, F. G., and P- Peck, D. L., 1959, Relations of certain Ryu, L, Niem, A. R., and Niem, W. A., 1992, Jurassic and Lower Cretaceous formations Schematic fence diagram of the southern in southwestern Oregon: American Tyee Basin, Oregon Coast Range: Oregon Association of Petroleum Geologists, v. 43, department of Geology and Mineral p. 2770-2785. Industries, Oil and Gas Investigation, v. 18, Irwin, W. P., 1964, Late Mesozoic orogenies in p. 28. the ultramafic belts of northwestern Saleeby, J. B., Harper, G. D., Snoke, A. W., and California and south western Oregon: U.S. Sharp, W. D., 1982, Time relations and Geological Survey Professional Paper 501- structural-stratigraphic patterns in ophiolite C 501-C, 1-9 p. accretion, west central Klamath Mountains, Niem, A. R., and Niem, W. A., 1990, Geology California: Journal of Geophysical and oil, gas and coal resources, southern Research, v. 87, p. 3831-3848. Tyee Basin, southern Coast Range, Oregon: Seeley, W. O., 1974, Geology of the State of Oregon, Department of Geology southeastern Dixonville quadrangle, and Mineral Industries, Open-File Report 0- Oregon: University of Oregon, Eugene 89-3,44 p. [M.Sc.], 77 p. Peck, D. L., Griggs, A. B., Schlicker, H. G., Snavely, P. D., editors, 1987, Tertiary Geologic Wells, F. G., and Dole, H. M., 1964, framework, neotectonics, and petroleum Geology of central and northern parts of the potential of the Oregon-Washington continental margin: Scholl, D. W., and et.al., eds., Geology and resource potential of the continental margin of western North America and adjacent ocean basins- Beaufort Sea to Baja California, Circum- Pacific Council for Energy and Mineral Resources, 305-355 p. Walker, G. W., and MacLeod, N. S., 1991, Geologic Map of Oregon: U.S. Geological Survey Special Map Series scale 1:500,000, P- Wells, R. E., Engebretson, D. C., Snavely, P. D., and Coe, R. S., 1984, Cenozoic plate motions and the volcano-tectonic evolution of western Oregon and Washington: Tectonics, v. 3, p. 275-294. DESCRIPTION OF MAP UNITS welded ash flow tuff; white to pale gray weathering, quartz and Surficial Deposits divided into: plagioclase phyric, crystal rich, trace white mica and epidote, Qls Landslide deposits (Holocene and rare rounded and resorbed biotite, Pleistocene?)~Chaotic mixture abundant opaques, mafic mineral of clay, silt, sand, gravel and generally badly altered, crystal boulders of weathered and fresh tuff; approximately 120 meters bedrock composition thick Qal Alluvial deposits (Holocene and Tac Andesitic conglomerate, Pleistocene?)~Alluvial deposits diamictite, and volcanic breccia consisting of unconsolidated or (Oligocene and/or Upper poorly consolidated; angular and Eocene?)-- Polymict volcanic sub-angular cobble, pebble, breccia, cobble conglomerate, gravel, and sand sized clasts, dacitic and andesitic volcanic poorly sorted commonly reddish rocks; 0 to 120 meters thick or yellow orange weathering Ta Andesite (Oligocene and/or Qfl Fluvial deposits (Holocene and Upper Eocene?)--Andesitic Pleistocene?)~Fluvial deposits rocks including amygdaloidal consisting of poorly sorted, well- flow breccia, dominantly rounded to subrounded; plagioclase porphyry plagioclase boulders, cobbles, pebbles, grit, and pyroxene porphyry, massive sand, silt and clay sized andesitic flows, and flow breccia, unconsolidated material locally columnar jointed; locally overlain by dacitic plagioclase Tdi Tertiary intrusive (Miocene and/or phyric unit; approximately 120 to Oligocene?)~Dominantly 180 meters thick glomero-porphyritic clinopyroxene phyric dikes with To Olistostrome (Oligocene and/or diabasic texture, + plagioclase Upper Eocene?)--Lahar, phyric phases, some dikes that olisostromal or mass flow cut Mesozoic basement and basal diamictite unit; disrupted Tertiary section may be feeder chaotically oriented blocks of dikes to Ta unit; some dikes also sedimentary and volcanic rock; cut Trl unit locally; contact locally deposited concurrently aureoles in Mesozoic rocks with andesitic flows and flow developed around largest of dikes breccia; approximately 60 meters thick Little Butte Volcanic Series of Peck and others (1964) divided into: Tc Colestin Formation (Upper Eocene?)~Sedimentary and Td Pyroxene dacitic andesite volcano-clastic rocks, basal (Oligocene?) -Pyroxene sedimentary unit consists of porphyry dacitic-andesitic flow, boulder, cobble and pebble abundant fresh interstitial conglomerate sandstone and clinopyroxene, larger pyroxene tuffaceous sandstone, pale phenocrysts commonly altered to whitish, orange and ochre chlorite, weathers reddish, weathering, well-rounded to grayish where fresh subangular clasts of Klamath lithologies including schistose Trl Rhyolite unit 1 (Oligocene?)-- graywacke, Riddle Formation(?) Rhyolitic moderately to poorly pebble conglomerate, porphyritic volcanic rocks, chert, angular to hornblende diorite, generally subangular arkosic sandstone massive, unfoliated or only very with little or no mica, and gritty- weakly foliated, white angular plutonic derived weathering, very deeply sandstone that resembles weathered and commonly friable; disarticulated, deeply weathered uralized or weakly diorite; poorly consolidated, metamorphosed to lower matrix supported, conglomerate; greenschist facies; quartz diorite clasts commonly imbricated; includes accessory apatite, marine fossils found at one sphene, trace white mica, green locality, massive red sandstone chlorite, and epidote. Green with well-developed groove casts hornblende and biotite are the observed at one locality, principal mafic phases. Quartz generally shallow marine to ranges from a few percent to nonmarine deposit, nonmarine about 30 percent facies predominate; approximately 300 to 400 meters JKgd Granodiorite (Jurassic and/or thick Cretaceous)--White weathering, coarse and medium grained Twt Umpqua Group, White Tail Ridge quartz, plagioclase, microcline, Formation (Lower Eocene)-- hornblende ± biotite bearing Conglomerate, pebble rock. Commonly static or conglomerate sandstone and unfoliated to very weakly shale; thick-bedded, medium- to foliated texture coarse-grained, mica-bearing lithic-feldspathic sandstone with JKhd Hornblende diorite (Jurassic minor interbedded mudstone; and/or Cretaceous)~Medium to very dark lithic, friable, blue- coarsely crystalline hornblende gray looking coarse sandstone to diorite composed of plagioclase, grit; abundant diverse fauna that hornblende, minor or no quartz, locally includes mollusks, and accessory magnetite, gastropods, and echinoids; some ilmenite, secondary epidote and coarse and carbonaceous plant- chlorite bearing siltstones. Some beds display large-scale trough cross- Metamorphic rocks bedding, some planar bedded. Conglomerate is generally matrix JKdt Dioritie tectonized rock (Jurassic supported. Clasts are rounded to and/or Cretaceous)~Strongly well rounded, very poorly sorted, foliated cataclastically and poorly to moderately-well graded ductilely strained dioritic rock; beds; locally, large continuous locally abundant dark mafic burrows are present in olive- dikes that are boudined, colored siltstone interbeds. lenticular or completely Generally pale buff to orange transposed into the foliation weathering. Mainly marine direction, strain fabric developed upper fan to delta complex under moderate greenschist facies; biotite, chlorite and epidote are present in tension fractures and replacing igneous Intrusive Complex hornblende and plagioclase in foliation surfaces; this fabric JKi Intrusive rocks (Jurassic and/or locally overprinted by secondary Cretaceous)~Granodiorite, silicification and metamorphism, quartz diorite, diorite and

10 types; unit is unmetamorphosed JKhf Mafic hornfels (Jurassic and/or and moderately indurated; locally Cretaceous)~Hornfelsic silicified with quartz veins near silicified mafic intrusive rock. major faults, thin-bedded Generally very dense hard rock siltstone and shale slightly in contrast to the commonly concretionary, mudstone-rich deeply weathered nearby facies locally very fossiliferous intrusive rocks. Locally very and bioturbated. Conglomerate coarse crystalline pegmatic clasts are very well-rounded, hornblende dikes nearby. poorly sorted and consist predominantly of mafic and JKag Augen gneiss (Jurassic and/or felsic volcanic rock, dark to gray Cretaceous?)~Strongly foliated, chert, diabase and volcanic banded medium-crystalline rock sandstone; dark green-brown consisting predominantly of weathering. Contains abundant hornblende-rich and plagioclase Buchia uncitoides of Lower + quartz rich layers. This rock Cretaceous, Berriasian age and appears to be tectonized possible Buchia elderensis or hornblende diorite and quartz piochii of Upper Jurassic, diorite that has undergone Tithonian age (William Elder, cataclasis and sub-mylonitic Per. comm.) deformation.

Sedimentary Rocks overlying Klamath Accretion Complex basement JKd Dothan Formation (Late Jurassic Myrtle Group (Late Jurassic to middle and Early Cretaceous)~Slate, Cretaceous)~Mudstone, fine and medium grained sandstone and conglomerate of metagraywacke, weakly to the Cretaceous Days Creek and moderately foliated, zeolite to Jurassic? and Cretaceous Riddle pumpellyite facies Formations. These units metamorphism, argillaceous represent forearc or foreland mudstone, and minor pebble and mass flow and channel deposits cobble conglomerate. that were deposited during the Graywackes are micaceous waning stages of the Nevadan quartzofeldspathic to lithic orogeny or just following. The composition. Regionally the unit Riddle Formation locally contains blocks of accreted unconformably overlies and is oceanic crust that includes fault bounded with the Late greenstone, pillow basalt, Jurassic Rogue Volcanics radiolarian chert, and shallow marine algal limestone, pelagic JKr Riddle Formation (Late Jurassic? foraminiferal limestone (Whitsett to Early Cretaceous)~Well- Limestone of Diller 1898) and bedded pebble to cobble blocks of metamorphic rocks conglomerate, volcanogenic including blueschist, metatuff, sandstone and shale deposited by metachert and amphibolite. The turbidity currents and mass flow Dothan is probably a post processes; locally interbedded Nevadan highly folded trench tuffaceous sedimentary rock and and trench-slope basin deposit volcanic breccia near the base; that was metamorphosed during conglomerate dominated by the Cretaceous. volcanic and dark chert rich clast

11 generally medium to coarse JKd2 Dothan Formation Semischistose grained, metamorphosed to (Late Jurassic and Early pumpellyite facies and lower Cretaceous)--Slate, phyllitic greenschist facies. Commonly siltstone, fine and medium chlorite and epidote bearing. grained metagraywacke, weakly Unit tends to weather dark rusty to moderately foliated where red thick-bedded, semi-schistose where thin-bedded, pumpellyite Jrs Serpentinized ultramafic rock facies metamorphism, (Jurassic?)~commonly foliated argillaceous mudstone with dark to pale green serpentinized minor pebble and cobble peridotite and serpentinite, where conglomerate. Graywackes are fresh weathers rusty, locally micaceous feldspathic to lithic in occurs in fault zones composition, locally contains abundant detrital epidote, white Jrvs Schistose Rogue Volcanics? (Late mica, chlorite and lesser biotite, Jurassic)~Extrusive and rare detrital quartzo-feldspathic hypabyssal intrusive rocks of clasts containing fine-grained mafic and intermediate euhedral brown hornblende; composition with penetrative locally very orange-red cataclastic and/or schistose weathering fabric, commonly very fine grained aphyric or plagioclase- pyroxene porphyry, extremely Western Klamath terrane rare thin-bedded intermediate and Jurassic continental arc complex! siliceous, thin-bedded, crystal- lithic, plagioclase phyric tuffs rv Rogue Volcanics? (Late Jurassic)- locally. Dense, dark green where -Extrusive and hypabyssal fresh, weathers rusty, locally intrusive rocks of mafic and contains pillow and pillow intermediate composition, breccia texture; metamorphosed commonly very fine grained to pumpellyite facies and/or aphyric or plagioclase-pyroxene lower greenschist facies, epidote, porphyry, extrusive rocks chlorite, sphene-bearing commonly amygdaloidal, assemblages extremely rare thin-bedded intermediate and siliceous, thin- Jris Schistose mafic intrusive unit bedded, crystal-lithic, plagioclase (Late Jurassic?)~Intrusive phyric tuffs locally. Dense, dark rocks, intermediate to mafic in green where fresh, weathers composition including gabbro rusty, locally contains pillow and and diorite, minor quartz diorite, pillow breccia texture. Locally generally medium to coarse hydrothermally altered and grained, metamorphosed to leached of mafic constituents, pumpellyite facies and/or lower also locally cut by dioritic dikes greenschist facies, epidote, of the intrusive complex chlorite, sphene-bearing assemblages; penetrative Jri Mafic intrusive unit (Late cataclastic and or schistose Jurassic?)~Intrusive rocks, fabric. Unit tends to weather intermediate to mafic in dark rusty red composition including hornblende gabbro and hornblende diorite with subordinate quartz diorite,

12 Map Symbols

Attitudes \ \ ® 12X Bedding: Inclined, vertical, horizontal Bedding: Top direction known & Bedding: Overturned V 36 Crumpled or disrupted bedding X\33 Xv Foliation: Inclined, vertical, horizontal

\52 X Foliation and Bedding: Inclined and vertical

Brittle or cataclastic foliation \eoX Dike orientation: Inclined and vertical ^43 Lineation

Overturned syncline, dashed where approximately located

Overturned anticline, dashed where approximately located

Contacts

Depositional contact: dashed where approximately located, dotted where concealed, queried where inferred s? 45 Fault, ball on down-thrown block, open arrow indicates dip where known, lineation symbol indicates rake of striae, dashed where approximately located, dotted where concealed, queried where inferred -A__.A ....A Thrust fault, teeth on hanging-wall, dashed where approximately located, dotted where concealed, queried where inferred

Low-angle normal fault, dashed where approximately located, dotted where concealed, queried where inferred

V67 Small faults with known dip

Strike-slip fault, paired arrows indicate relative displacement Fossils Localities Lane Mountain Quadrangle ** Map Sample Fossil Name Age Environment No. No

1. 1LM-92 Brachiodontes cowlitzensis Paleocene E Oligocene Nuculana sp. Venericardia sp.

2. 4 LM-92 Naticid genusindet ? Brachiodontes sp. indet. ? Macoma sp. indet. ? Cadulus sp. indet.

3. 9 LM-92 Turritella sp. Acanthocardia brewerli E. Eocene mid Eocene 20-185 meters

4. 10 LM-92 Brachiodontes cowlitzensis? Glycymeris sp. indet. Microcallista convadiana L. Paleocene - Late Eocene 0-50 meters

5. 11 LM-92 Turriletta sp. indet E. Eocene - late mid Eocene Acanthocardic brewerii 20-185 meters ? Corbula sp. indet. Microcallista convadiana ? Venericardia sp.

6. 12 LM-92 Turritella sp. indet. Cadulus sp. indet. 20-185 meters

7. 16 LM-92 Turritella sp. indet. E. Eocene - late mid Eocene Acanthocardia brewerii Microcallista conradiana 20-185 meters Dentalium sp. indet.

8. 92 LM-2 Turritella sp. indet. L. Paleocene - L. Eocene Brachidontes cowlitzensis Microcallista conradiana

9. 92LM-10 Fusunus sp. indet late-early to early-middle Eocene not deeper than 50m Acila (Truncacila) decisa Brachidontes cowlitzensis Clinocardium? sp indet Dentalium stentor Schizaster diabloensis

10. 93LM-3 Buchia uncitodies Berriasian

11. 93LM-11 Micrcallista conradiana late Paleocene to late Eocene 20-180 meters Nemocardiwn sp. mdet post-mortum transport

12. 93LM-12 Cylichnina tantilla Eocene 20-180m Turritella sp .indet Naticid genus indet. Brachidonts cowlitzensis Microcallista comradiana ? Periploma sp. indet. Venericardia sp. indet

13. 93LM-19 Buchia cf. piochii Middle?-Late Tithonian

14. 93LM-25 Venericardia sp. indet.

**Terrtiary fossils identified by Loius Marankovich; Mesozoic fossils by Will Elder