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Geologic Map of the Naples Quadrangle, Boundary and Bonner

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Geologic Map of the Naples Quadrangle, Boundary and Bonner IDAHO GEOLOGICAL SURVEY DIGITAL WEB MAP 109 MOSCOW-BOISE-POCATELLO WWW.IDAHOGEOLOGY.ORG MCFADDAN AND OTHERS GEOLOGIC MAP OF THE NAPLES QUADRANGLE, BOUNDARY AND BONNER COUNTIES, IDAHO correl ation of map units Disclaimer: This Digital Web Map is an informal report and may be revised and formally published at a later time. Its content and format Colluvium and may not conform to agency standards. Made Alluvial and Mass Wasting Glacial and Mark D. McFaddan, Roy M. Breckenridge, Russell F. Burmester, and Reed S. Lewis Deposits Lacustrine Deposits Deposits Related Deposits m Qal Qlm Qc Qglc Holocene 2009 Qgl Qgf Qgt Qgls Quaternary Pleistocene Kd 40 Qgt Qgt Kgfc Ktsp 60 Qgl Kgfc 75 Qglc Qgl 10 Intrusive Rocks 45 Qal Kgfc Ktsp 60 Qgt Qglc Tl Tqm Eocene Tertiary 20 Qgt Qglc 25 25 Qgl 40 Qc Qc 70 Ktsp Ktsp Qgt Ktsp 45 Qgl 35 Ktsp Qgl m 45 TKt Kgf 48 8 Kpeg 60 Qglc Kum Kgu Kgfc 15 Qal Cretaceous 75 Qal 65 Qgl Kmg Qglc Qgl Qgt Qgl 75 Qgl Kgkp Kgfc Ktsp Kd 80 Qgf Ktsp m 50 Ktsp Ktsp Qglc Metasedimentary 70 Rocks Kgfc 80 20 Qal Ymi 20 Ypab 80 80 25 Qal Ya m 85 25 Ypmt Mesoproterozoic 70 Qgf 25 Ypgs Ktsp Qgl Qal Kgfc Qgl 25 Qglc Qglc Qgt 85 Qglc INTRODUCTION susceptibility about 5 x 10-3 SI). Known only in southeast part of map area, The pre-Eocene ages suggest that some uplift was Cretaceous. A small fault Qgt Qgl Qgl although similar dikes occur about 20 km both southwest and north-h- with apparent west side up reverse movement south of Bloom Lake could Qgt Qglc northwest in metasedimentary rocks of the Priest River complex. Age based record a late episode of contraction. The sense of motion is the same as for 40 Qglc Quaternary deposits on this 1:24,000-scale quadrangle were mapped in on interpretation that it is intruded by Kpeg and Kgf in the Moravia quad- the Purcell Trench fault, but uplift of the western block during the Late Qglc Qgl 1987-8 and 2007-8 by R.M. Breckenridge. Bedrock was mapped in 2008 rangle to the north. Cretaceous would juxtapose metamorphic grades and still result in old m Ktsp Qgl by M.D. McFaddan, R.F. Burmester, and R.S. Lewis, and augmented with uplift age to the west. Zones of intense development of fabric in Ypab east Kmg Muscovite-biotite granite (Cretaceous)—Medium-grained muscovite-biotite 30 mapping by F.M. Miller (1981, 1993-4), R.F. Burmester (1985) and P.T. of the lithologic contact could have accommodated distributed Qc granite exposed in a single mass in the southern edge of the western part of 75 Ktsp Doughty (1995). Plutonic rock descriptions are modified from Miller and deformation, broadening uplift ages across the zone. However, the 45 Qgl Burmester (2004). the map. Possibly related to Kgf, or Kpeg. penetrative fabric appears inconsistent with formation during Eocene Ktsp Qal Ktsp Qgf extensional faulting if these rocks were already cool below mica closure Qal Qglc Kgu Granitic rocks undivided (Cretaceous?)—Granite to tonalite in small exposures Ktsp Qglc Moderate grade Precambrian metasedimentary rocks of the Prichard Form-m- temperatures. Instead, it is more consistent with formation during Kgfc Qgt too indistinct or isolated to relate to larger map units. Small exposure near ation, Belt-Purcell Supergroup are exclusively present in the southeastern juxtaposition of the two rock types across this contact during Cretaceous (or Kgfc Tl part of the Naples quadrangle. Cretaceous granitic rocks dominate bedrock the southern map boundary is granodiorite with 5 mm equant quartz and subhedral feldspars, and 4 mm books plus flakes of biotite. It contains earlier) contraction. Qgl of other, non-Quaternary exposures, with inclusions and septae probably 75 abundant inclusions of Ypmt and is associated with aplite and pegmatite Qc 60 derived from the Prichard Formation most abundant in the southwestern So, where is the Purcell Trench fault? We cannot rule out the possibility that part of the quadrangle. dikes. the Ypmt-Ypab lithologic contact accommodated some extension, since Qgl Ktsp m Kgfc Granodiorite of Falls Creek (Cretaceous)—Chiefly granodiorite, but may lack of exposure could result from erosion of breccia along it. A splay of the 25 The quadrangle is located in the Purcell Trench, a major structural and Purcell Trench fault may also be buried in the trench and account for lack Kgfc Qglc include some tonalite. Plagioclase averages sodic andesine. Color index Ktsp Qgt Qgf Qal physiographic feature that trends north-south over 80 miles within the Qgl averages 10. Biotite only mafic mineral. Minor muscovite present locally; of continuity of Kmg across it as well as weakness that aided erosion of the Qgl Idaho Panhandle. This part of the trench is drained by Deep Creek, a trench. This splay may continue north to the north edge of the map, passing Ktsp tributary of the Kootenai River which flows west from Montana to Bonners probably primary. Accessory minerals include epidote, allanite, apatite, Qgt Qgf Qglc west of Round Mountain and be responsible for chloritic alteration there. Qal Qglc Qglc zircon, and opaque minerals. Medium- to coarse-grained; generally seriate. 25 Ferry and then northward into British Columbia. During Pleistocene Alternatively, the fault there could be continuous with the hypothesized 35 glaciations, a lobe of the Cordilleran Ice Sheet repeatedly advanced Texture and grain size more varied than in tonalite of Snow Peak (Kpsp) to Qal Ypmt-Ypab contact fault. Eocene faulting likely also accounts for brittle Qgl east. Unit contains abundant fine- to coarse-grained leucocratic dikes and 10 southward along the Purcell Trench from Canada. Tributary valley glaciers deformation in the exposures southwest of Ruby Creek. This could be the Qgt 20 25 pods. Composition, texture, and concentration of included leucocratic Kgfc Qgl from the Selkirk Range to the west and Cabinet Range to the east southern continuation of the northern Purcell Trench fault in the Moravia 40 Ktsp Qglc rocks vary greatly over short distances in much of unit. 30 contributed to the ice stream. The ice dammed the Kootenai River, formed quadrangle to the north or one of its splays, but it has no obvious southward Qgt Qlm Glacial Lake Kootenai, and diverted the outlet southward down the trench Ktsp Tonalite of Snow Peak (Cretaceous)—Biotite tonalite, ranging to granodiorite. projection. Thus, the Purcell Trench fault in the Naples map area may be a Qc Qgls into the Pend Oreille and Spokane River drainages. Thick sections of glacial Qlm Unit is characterized by abundant pale-green epidote with allanite cores, right-stepping en echelon fault system. Qglc till, outwash, and lacustrine deposits filled the depression of the Purcell 45 easily seen in nearly all exposures, and by large, pale, lavender-gray quartz. 30 45 Trench. Near McArthur Lake, the trench narrows and is filled by a pitted Qgt Ktsp Qc Qglc Average plagioclase composition is intermediate andesine. Typically 20 end moraine. After retreat of the continental ice, the northward drainage of Qgl contains almost no potassium feldspar, but scattered phenocrysts present Tl Qgl the Kootenai River was restored. The presence of Glacier Peak tephra locally. Quartz commonly elongated into crude, rod-shaped grains up to Qglc (11,200 B.P.) gives a minimum date for retreat of the ice lobe from the SYMBOLS Qal 1.5 cm long. Biotite is only mafic mineral in typical Ktsp; color index 11 to 35 trench (Richmond, 1986). Alpine valley glaciers persisted until nearly 17 is higher than most units in Priest River complex. More mafic and finer Contact: dashed where approximately located. Ktsp m 10,000 years ago in the higher cirques of the Selkirk and Cabinet Ranges. grained variety occurs as dikes in southern part of quadrangle. Muscovite Qglc Holocene alluvium, colluvium, and lacustrine sediments are mostly the Qgt Qal generally absent, but found sparsely and irregularly in westernmost part of Fault: dashed where approximately located; dotted where concealed; Qgl Qgl Qglc product of reworked glacial deposits. unit; probably secondary. Medium- and coarse-grained; seriate in much of bar and ball on downthrown side. Qgls Qgf unit. Subtle to prominent foliation and lineation irregularly developed. Qglc Abundant irregularly shaped mafic inclusions ranging from 1 cm to tens of 20 Strike and dip of bedding. Qgt DESCRIPTION OF MAP UNITS meters occur throughout unit. Composition and texture are much more Qal m uniform than in most Priest River complex units, but are increasingly varied Ktsp Qgls 65 Strike and dip of bedding; ball indicates bedding known to be toward gradational contact with Kgfc, around concentrations of mafic Qglc Qgl upright. Intrusive rocks are classified according to IUGS nomenclature using inclusions, and near and east of the range front northwest of Round Moun- normalized values of modal quartz (Q), alkali feldspar (A) and plagioclase tain. There, variation is extreme; some rocks are highly porphyritic and 85 Strike and dip of bedding; overturned bedding. 30 Qgl Qglc Qgl Ktsp (P) on a ternary diagram (Streckeisen, 1976). Mineral modifiers are listed in contain hornblende and sphene. These are characteristics of the granodior- Qgt Qglc 85 Strike and dip of bedding; strike varied. 20 Qal order of increasing abundance for both igneous and metamorphic rocks. ite of Kelly Pass and granodiorite of Bonners Ferry, which are not part of 75 10 5 Qc Grain size classification of unconsolidated and consolidated sediment is Priest River complex. Mixing of intrusions with affinities for both sides of Strike and dip of compositional layering. Qglc 30 Qgl based on the Wentworth scale (Lane, 1947). Bedding thicknesses and the Purcell Trench is consistent with there being little displacement across 4 80 Qal Qglc lamination type are after McKee and Weir (1963), and Winston (1986).
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