Need help with GEO - Assignment - Week 6

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Lab Activity 

Using the geologic map of Virginia, answer the following questions: GEO101_Lab6_Module6_Map.pdf 

  1. Is the region in the extreme northwest corner to the Potomac River strongly folded or strongly faulted? 
  2. Is the region from the southeast corner to Harrison Island along the Potomac strongly folded or strongly faulted?
  3. In the southwestern part of the map, along the Shenandoah River, the sediments are only Quaternary in age, yet they are surrounded by much older Cambrian sediments.  How do you explain this? 
  4. In the southeastern corner of the map, locate Rockville and Gaithersburg.  Notice that they are separated by the Plummer’s Island Fault.  Is Rockville moving atop Gaithersburg or is Gaithersburg moving atop Rockville? 
  5. Find Martinsburg, WV, in the extreme northwest corner.  Now locate Martinsburg, MD, which is just to the to the east of Harrison Island and Mason Island along a bend in the Potomac in the south central area of the map.  Which is surrounded by the older rock? 
  6. Locate Long Marsh Run just south of the West Virginia/ Virginia border on the southwestern side of the map.  Which way is it flowing?
    How many different ages of rock would you encounter along its course?
  7. In the middle image at the bottom, to the far right, you see that the younger Prettyboy Schist lies beneath the older Mather Gorge Formation.  How can older rock be found atop younger rock? 
  8. Locate the oval, brown rocks near the center of the map.  What geologic feature is this?


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U.S. DEPARTMENT OF THE INTERIOR SCIENTIFIC INVESTIGATIONS MAP U.S. GEOLOGICAL SURVEY Obps Osnr 25 63 Obs 50 75 58 70 50 80 40 40 25 L 16 68 75 88 55 |td 27 |td Obs Obrr 73 Obps 23 78 84 |e 6 19 74 34 25 60 81 Osnr 39 70 22 3 75 44 Obps 58 Obss Obrr Obs 16 35 87 9 81 31 53 82 35 50 20 47 30 45 45 25 64 55 60 Obss 70 45 30 86 45 26 68 60 25 Obs 45 |cb 35 26 77 O|c |t QTt |ch F 80 50 |ca 20 75 25 |cb |t 5 70 |wact |wac |e 80 40 QTt 85 45 60 45 |ch 21 QTt |ca 70 |cwo 18 30 |chs 45 40 24 Qa 27 50 80 45 52 |war 20 Qt 70 30 55 55 44 Qt 15 35 |cwo 58 |war |ch Qt QTt 54 60 |ca 50 26 75 |chs 60 |ch 46 Ygt Qcc 40 |cwo 44 40 15 22 57 |cwm 20 15 Qcc Zcm Zrc 60 Zcp Zss 30 Zrd 70 Zmd Ya Qa Ypb Qa Ylg 65 85 Ylg 70 Qa Yc 53 36 72 70 45 60 45 Yq 65 Jd 15 30 47 Yp Ygt Ya Zmd Jd Ymc 25 Yp Qa Zmd 44 Zfsm 45 Base from U.S. Geological Survey, 1984 1983 North American datum 25,000-foot grid ticks based on Georgia coordinate system, west zone 10,000-meter Universal Transverse Mercator grid ticks, zone 16 J^tm Ql 27 FAULT OU NTA IN QTt 11 44 27 Qt 65 Qt |Zmg Qa ^cbg QTt S Jdh Jdc Jd ^cbb 22 19 28 24 38 30 Jd 45 30 48 68 45 Qa 55 35 37 23 50 34 35 ^cmp Qa 45 Ob 78 |Zmm 60 50 |Zmg |Zmg 67 Ob 80 |Zmm Au 85 Qa 36 Qa |Zmp 66 55 77 S Qa Oq 45 Odl |Zn 80 SCALE 1:100 000 1 0 1 3 2 6 7 ET IC N O R TH TRUE NORTH MAGN 0 1 3 2 4 5 6 7 10 KILOMETERS 9 8 VIRGINIA CONTOUR INTERVAL 10 METERS 80 Qcf Fine colluvium Qcc Coarse colluvium Obrr SEA LEVEL Obps Obrr Om |lu 45 67 |cb O|c 85 Oc Kps Osnr |wa |cb 2000 3000 |ch |ca |t |ch |ca |tb |tf |td |e |tbh Zcm Ybg Obps Zmd Zrd Yg |cwm |ch Zcm |clp |cwb ^cmp ^cmt |wa |ca |ar |clp |uq |uq |uq |Zsb |e |Zsmp |Zmbq |Zmbs |Zms |Zmbs STATE ROUTE 97 PLUMMERS ISLAND FAULT |Zsmp |Zsb |u |uq |Zsq |Zsb |Zip |Zss |fr |Zmg |Zmp SEA LEVEL |Zu |Zsb |Zsc |wa Undivided—Shown in cross section only Tomstown Formation (Lower Cambrian) |tb Zmd Ymc Zmd SEA LEVEL 1000 |chs |wac |t Ypg |cwm Yml Zcma Zfcr Zfsm Ypg Jdh J^tm |Zmg ^cbb |Zms ^cbb Jdh |Zmp |s |s INTERSTATE ROUTE 495 Tomstown Formation (Lower Cambrian) |cp Carbonaceous phyllite (Lower Cambrian) ^cbb ^cmp Zfsc |Zmbs ^cmr |Zmbs Harpers Formation (Lower Cambrian) |Zu |s Ogh |s Ok |l |lu Metasandstone and schist |fr Rocky Springs Station Member Fauquier Group Zfcr Ogp Ob 1000 |lu Swains Mountain Formation (Neoproterozoic) Zfsm Metamudstone Zfsc Boulder conglomerate Zrc Cobbler Mountain Alkali Feldspar Quartz Syenite of the Robertson River Igneous Suite (Neoproterozoic) Ypb Megacrystic metagranite (Mesoproterozoic) Ybg Biotite granite gneiss (Mesoproterozoic) Yml Pink leucocratic metagranite (Mesoproterozoic) Yg Ogh Quartzite Garnetiferous metagranite (Mesoproterozoic) Yqp Quartz-plagioclase gneiss (Mesoproterozoic) Ym Marshall Metagranite (Mesoproterozoic) |f Undivided |Zmp |Zmt |Zl |Zn Lower Cambrian and (or) Neoproterozoic |Zlm Ymc Coarse-grained metagranite (Mesoproterozoic) Ypg Porphyroblastic metagranite (Mesoproterozoic) Yhm Hornblende monzonite gneiss (Mesoproterozoic) Urbana Formation (Lower Cambrian?) |um Marble |uq Quartzite Sugarloaf Mountain Quartzite (Lower Cambrian) |squ Upper member |sqm Middle member |sql Lower member |sq Undivided--Shown in cross section only |Zw Sams Creek Formation (Lower Cambrian? and Neoproterozoic?) |Zsb Metabasalt |Zsf Felsic schist |Zsm Marble |Zshp Hematitic phyllite |Zsl J^tm High-titanium quartz-normative late cumulates Granophyre Thermally metamorphosed rocks (Lower Jurassic and Upper Triassic) Jms Jmss Jmt Jmh Jmhs Jmmc Turkey Run Formation (Lower Jurassic) Conglomerate Hickory Grove Basalt (Lower Jurassic) Sandstone and siltstone Midland Formation (Lower Jurassic) J^ccg Conglomerate |clp Phyllite Zcm Metabasalt Zcs Metasedimentary phyllite Zcp Tuffaceous phyllite Zcr Metarhyolite 4000 Zmd Mount Zion Church Basalt (Lower Jurassic) Catharpin Creek Formation (Lower Jurassic and Upper Triassic) Goose Creek Member Metarhyolite dike (Neoproterozoic) Quartz-rich schist |Zmg Metagraywacke |Zmm Migmatite |Zmp Phyllonite |Zmt Metatuff |Zsd Soldiers Delight Ultramafite (Lower Cambrian and (or) Neoproterozoic) |Zu Mafic and ultramafic rocks (Lower Cambrian and Neoproterozoic) |Zg Metagabbro and metapyroxenite (Lower Cambrian and Neoproterozoic) Potomac Formation (Lower Cretaceous) EXPLANATION OF MAP SYMBOLS Contact—Dotted where concealed Metalimestone Lake bed—Dotted where concealed Quartzite interbedded with phyllite |Zsq Quartzite |Zss Metasiltstone Thrust fault—Sawteeth on upper plate |Zsc Calcareous metasandstone Normal fault—Ball and bar on downthrown side FAULTS (Dashed where inferred; dotted where concealed) Reactivated fault—Open ball and bar on downthrown side of early normal fault and sawteeth on upper plate of later thrust fault; shown in cross section as a double-headed arrow Ijamsville Phyllite (Lower Cambrian? and Neoproterozoic?) |Zip Phyllite |Zib Metabasalt |Ziq Quartzite |Zim Marble Overturned thrust fault—Bar on upper plate; sawteeth show direction of dip Strike-slip fault—Arrows show relative movement Unclassified |Zil Metalimestone |Zic Phyllitic conglomerate Shear zone |Zicm Conglomeratic metagraywacke |Zicp Chloritic phyllite PLANAR FEATURES (May be combined with linear features; where features are combined, intersection of symbols marks point of intersection) Strike and dip of bedding 32 Marburg Formation (Lower Cambrian? and Neoproterozoic?) |Zmbs Metasiltstone |Zmbg Metagraywacke |Zmbb Metabasalt |Zmbq Quartzite |Zp Inclined 44 Overturned Vertical Horizontal Strike and dip of Mesoproterozoic foliation including compositional layering 77 Inclined Prettyboy Schist (Lower Cambrian? and Neoproterozoic?) |Zpb Metabasalt |Zpq Quartzite Vertical Strike and dip of first-generation (S1) Paleozoic cleavage and (or) schistosity 47 Inclined Vertical Potomac Terrane Dp Pegmatite (Late Devonian) Dg Guilford Granite (Late Devonian) Oq Quartz bodies (Ordovician) ^cbb Balls Bluff Member Ong Quartz gabbro ^cbl Leesburg Member Onu Ultramafic rocks Ontr Trondhjemite Manassas Sandstone (Upper Triassic) ^cmp Poolesville Member ^cmt Tuscarora Creek Member ^cmr Reston Member Grove Formation (Lower Ordovician and Upper Cambrian) O|gu Upper member O|gl Lower member Strike and dip of second-generation (S2) Paleozoic cleavage and (or) schistosity 60 Inclined Vertical Strike and dip of mylonitic and phyllonitic foliation 75 Inclined Norbeck Intrusive Suite (Late Ordovician) Biotite-hornblende tonalite Frederick Valley Synclinorium Metadiabase dike (Neoproterozoic) |Zms Kps Groveton Member Marble Mather Gorge Formation (Lower Cambrian and (or) Neoproterozoic) COASTAL PLAIN PROVINCE Ont ^cbg Northwest Branch Formation (Lower Cambrian and Neoproterozoic) Conglomerate Chatham Group Jcm Semipelitic schist and meta-arenite |Zlm |Zsqp Sander Basalt (Lower Jurassic) Sandstone and siltstone Upper part Wakefield Marble (Lower Cambrian? and Neoproterozoic?) Amphibolite (Mesoproterozoic) High-titanium quartz-normative early cumulates Laurel Formation (Lower Cambrian) |Zn Ya Jdc |l Loch Raven Schist (Lower Cambrian and (or) Neoproterozoic) |u Muscovitic phyllite Crystalline diabase Sykesville Formation (Lower Cambrian) |Zl |Zsmp Jd |s Oella Formation (Lower Cambrian and (or) Neoproterozoic) Charnockitic granite (Mesoproterozoic) Culpeper and Gettysburg Basins Bear Island Granodiorite (Ordovician?) |Zo Yc PIEDMONT PROVINCE Ob Araby Formation (Middle and Lower Cambrian) Tuffaceous phyllite Quartzite and quartz-sericite tectonite (Mesoproterozoic) Muscovitic trondhjemite |ar |Zstp Yq Odt |lu Layered granitic gneiss (Mesoproterozoic) Garnet-graphite paragneiss (Mesoproterozoic) Leucocratic muscovite-biotite monzogranite Cash Smith Formation (Upper and Middle Cambrian) Ylg Yp Odl |cs Undivided |clc Zrd X Shale Westminster Terrane J^cc Buzzard Knob Member Zcma Ob White leucocratic metagranite (Mesoproterozoic) Ygt Catoctin Formation (Neoproterozoic) 3000 Jd GEOLOGIC MAP OF THE FREDERICK 30' Maryland Heights Member Loudoun Formation (Lower Cambrian) 2000 Ogg Carter Run Formation (Neoproterozoic) |frs Bull Run Formation (Upper Triassic) 2000 SEA LEVEL |Zms Ok LINEAR FEATURES (May be combined with planar features; where features are combined, intersection of symbols marks point of intersection) 40 Ogh Biotite-hornblende tonalite Ogg Quartz gabbro Ogp Metapyroxenite Dalecarlia Intrusive Suite (Early Ordovician) Biotite monzogranite and granodiorite Bearing and plunge of axis of minor fold OTHER FEATURES Location of isotopically dated rock—Sample dated by U-Pb dating techniques Kensington Tonalite (Middle Ordovician) Georgetown Intrusive Suite (Early Ordovician) Odm Vertical L Quarry or mine, active and inactive—Abbreviations are as follows: Ag, silver; Au, gold; C, chromite; Cu, copper; D, diabase; F, hematite, limonite, manganese, and iron ore; L, limestone; M, marble; Pb, lead; S, building stone; Sl, slate; Zn, zinc Radon in soil gas—Shown where greater than 200 pCi/L (Gunderson and others, 1988) Small sinkhole—Less than or equal to 50 m2 in diameter Large sinkhole 60' QUADRANGLE, MARYLAND, VIRGINIA, AND WEST VIRGINIA By Scott Southworth, David K. Brezinski, Avery Ala Drake, Jr., William C. Burton, Randall C. Orndorff, Albert J. Froelich, James E. Reddy, Danielle Denenny, and David L. Daniels 3 Zss Owens Creek Member |cwb 1000 |Zmt 2 Adamstown Member Jmm Metasandstone |cwmq NO VERTICAL EXAGGERATION 1 |fa Jmtc Antietam Formation (Lower Cambrian) |cw Silver Spring |s Ogh |Zu |Zms |Zmg Jdc |Zmm |Zmp |Zmm |Zu |ch 1000 meters = 3281 feet Surficial deposits are not shown ^cbb |Zmg |Zu |Zms |Zmg |Zms Cabin John Creek WASHINGTON AND OLD DOMINION RAILROAD REGIONAL TRAIL Broad Run ^cbg Jd ^cmr ^cmp J^tm Jdg J^ccg ^cbb J^tm LT U FA |ca Ylg Yp Yp Yq Yp Jd Jdh VE O GR 4000 |cwo Jdh J^tm T |war J^cc ^cbb Phyllite Jdg |t |cwm METERS 3000 AN |ch J^cc J^ccg Jcm Jmm J^tm Yp |ca |wact Zcm Ym Zcp |cw S EA PL 3000 Ylg Yc |t 2000 Zmd Yml |ch O|c Ym Zmd INTERSTATE ROUTE 495 Zmd Ogh ROCK CREEK SHEAR ZONE Yq Zmd PLUMMERS ISLAND FAULT Zss STATE ROUTE 190 |cwb Zcm Zcp STATE ROUTE 7 |cwm |cwo |ch Zsp Benevola Member BLUE RIDGE PROVINCE 4000 INTERSTATE ROUTE 495 |t |ca |chs INTERSTATE ROUTE 270 |e |ca |war |wac |cb |wact |e |e |e Lime Kiln Member Jdh 3000 B' J^tm |Zmg |Zmm Frederick Formation (Upper Cambrian) |fl Bolivar Heights Member |cwo Ogg |Zms Meriden Group POTOMAC TERRANE |Zmg |Zg Neoproterozoic Marble Dargan Member Fort Duncan Member |tf 1000 |Zp |Zms |Zmg |Zu Zsm Diabase dikes and sills (Early Jurassic) Weverton Formation (Lower Cambrian) |Zmg Swift Run Formation (Neoproterozoic) 2000 POTOMAC RIVER |cb J^cc 1,153±6 Ma Elbrook Limestone (Upper and Middle Cambrian) Chilhowee Group Sugarland Run 1000 Zcm Zss Goose Creek CATOCTIN MOUNTAIN 2000 BULL RUN MOUNTAIN FAULT U.S. ROUTE 15 3000 Ylg* Big Spring Station Member (Upper Cambrian) |tbh CULPEPER BASIN Black Oak Ridge 4000 1,149±19 Ma Conococheague Limestone (Lower Ordovician and Upper Cambrian) Red Run Member PIEDMONT PROVINCE SHORT HILL FAULT BLUE RIDGE B SHENANDOAH RIVER METERS Yhm* Stoufferstown Member |chs BLUE RIDGE-SOUTH MOUNTAIN ANTICLINORIUM |Zo |Zsd Mesoproterozoic Stonehenge Limestone (upper part) (Lower Ordovician) |war |ch GREAT VALLEY SECTION 1,144±2 Ma Rockdale Run Formation (Middle and Lower Ordovician) Cavetown Member 4000 BLUE RIDGE PROVINCE Ypg* Pinesburg Station Dolomite (Middle Ordovician) |wact |ca VALLEY AND RIDGE PROVINCE |Zpb |Zmbs |Zmbq |Zp |Zsqp |Zpq |Zsq Sugarloaf Mountain Anticlinorium and Bush Creek Belt Chewsville Member NO VERTICAL EXAGGERATION 1000 meters = 3281 feet Surficial deposits are not shown 1,140 Ma St. Paul Group (New Market and Row Park Limestones, undivided) (Middle Ordovician) |td |s |Zsb Zcm Yhm |Zmbg Yq |wac |t 1000 |Zsb |sq Ymc* Waynesboro Formation (Lower Cambrian) METERS 2000 |Zsb |sq |Zmbb Chambersburg Limestone (Middle Ordovician) 3000 |Zmbq Zcm |ca |ch |cw Monrovia |Ziq |Zip |u Yhm |ch BARNESVILLE-MONROVIA THRUST FAULT MARTIC FAULT SUGARLOAF MOUNTAIN ANTICLINORIUM MARTIC FAULT Monocacy River INTERSTATE ROUTE 270 MARTIC FAULT |Zip |fa |cw |t |t Jd |ar ^cbl Zcm |fr |frs |ca |cwm |cwb |clc |cwb |fa |fr POTOMAC TERRANE PLEASANT GROVE FAULT Zrd INTERSTATE ROUTE 70 CATOCTIN MOUNTAIN Catoctin Creek SOUTH MOUNTAIN Zsm Yg |cwo Zcr |cwm |cwo |wa |e |cb |cw Zcm |tbh |e O|c |t |ca |frs |fr 1,111±2 Ma to 1,112±3 Ma Beekmantown Group 4000 HYATTSTOWN THRUST FAULT |wac |e |wact |war |td Obss Obss BLUE RIDGE KEEDYSVILLE FAULT Antietam Creek Sharpsburg |e O|gl O|gu |fl |Zsmp PROTEROZOIC Martinsburg Formation (Upper and Middle Ordovician) |cb INTERSTATE ROUTE 70 |cb O|c |ch Ym* Great Valley Section A' |Zsb 1,077±4 Ma Terrace deposit, high level (Pleistocene and Tertiary) T RN Ogh WESTMINSTER TERRANE Bush Creek Obs |ca |chs |ch |war Ybg Zss Zmd Frederick Oc Om Obs 4000 POTOMAC RIVER Rockymarsh Run Osnr Oc Om Obps |e 1000 Obss Yqp* VALLEY AND RIDGE PROVINCE Obrr FREDERICK VALLEY SYNCLINORIUM U.S. ROUTES 15 AND 340 |cb O|c Osnr Oc STATE ROUTE 67 |cb O|c |e BULL RUN MOUNTAIN FAULT 1000 Opequon Creek 2000 Opequon Creek 3000 U.S. ROUTE 11 INTERSTATE ROUTE 81 4000 MASSANUTTEN SYNCLINORIUM A STATE ROUTE 9 METERS CULPEPER BASIN 1,077±4 Ma Lag gravel (Holocene and Pleistocene) |l PIEDMONT PROVINCE BLUE RIDGE-SOUTH MOUNTAIN ANTICLINORIUM |Ziq |Zshp |Zsl Dp O|c GREAT VALLEY SECTION Ygt* Residuum (Holocene and Pleistocene) Obss BLUE RIDGE PROVINCE 1,060±2 Ma Terrace deposit, low level (Holocene and Pleistocene) Obs VALLEY AND RIDGE PROVINCE Yg* Qt QTt MAP LOCATION NATIONAL GEODETIC VERTICAL DATUM OF 1929 APPROXIMATE MEAN DECLINATION, 2007 1,059±2 Ma Alluvium (Holocene) Ql Geology mapped from 1989 to 1994 Digital compilation by James E. Reddy and Danielle Denenny Geologic map editing by Elizabeth D. Koozmin Digital cartography by D. Paul Mathieux 8 MILES W. VA. 1 57 B' MARYLAND 5 4 Yml* 83 60 80 25 FA Jmh 101/2° 1,055±4 Ma Qa Qr Dg T |lu 62 77 |Zmp Ogp Dg Dp 35 Ok 40 65 |Zl 38 Qa Ogg Oq Odm 80 Ybg* Colluvium (Holocene and Pleistocene) Dp S 50 Ogp |Zu Ok 60 80 78 S S 48 Ok 50 |Zmp Ogh 75 50 45 35 65 68 40 50 45 Oq |Zmp 60 42 67 70 47 50 40 Ok 50 85 |Zmt |Zms |Zmg 50 80 |Zmm Qa 8 10 33 |Zmp 1,055±2 Ma UNCONSOLIDATED SURFICIAL MATERIALS 25 Ok Ont 75 45 15 77 65 45 35 Oq 80 |Zmp 65 60 Qa 55 67 3 65 43 25 |Zu Ob 80 |Zu |Zmp Ob 85 Ogh Ypb* Qa 60 Ont 80 |s 40 65 70 Ong 57 722±3 Ma [Map units are shown generally from west to east. For descriptions, please see accompanying text pamphlet.] Ok 55 Ont |Zss |Zw |Zsb |Zsc |Zsf Ya Yp 30 70 Oq Au 55 80 75 Ont Ont Zrc* LIST OF MAP UNITS 60 52 78 80 60 |Zic |Zstp Qa 60 40 70 83 70 |Zmg 80 Ok |s 83 |Zmp Stratified rocks |Zsm |lu |Zl Ont 43 55 80 60 Onu 68 80 73 |Zmg 36 |Zmm Ont 80 75 |Zib |Zil Zrd* |Zicm |l Yc Ok 35 Ont Ong Qa 45 Au 70 7 40 Ont 42 60 |Zicp |s 571.5±5 Ma 45 Ok Oq Odm Oq Ong |Zmg WESTMINSTER TERRANE |sqm 50 Onu Ong |Zmp 78 65 85 27 37 40 J^tm Jd 27 83 78 20 |Zu 8 33 ^cbb 56 50 45 70 |s 80 22 40 Qa 77 |Zmm |Zu |Zms 40 45 15 ^cmr S 17 13 30 40 10 8 21 Ql J^cc 73 Jd Jd Jdh 45 QTt |Zu Qa 80 70 32 43 17 25 24 50 55 47 Qa QTt 12 22 75 |Zu |Zmg 45 10 20 J^tm 35 43 20 37 Jmss 10 S S S 14 20 ^cbb 77 Jd QTt Qa Qt |Zu 85 |Zms 30 Oq S 42 45 20 50 7 Jdc |Zmg 35 15 15 30 S Jms 36 25 ^cmr Qcc J^ccg Qa |cw Zcp Zcma ^cmp 85 Zss Ont 80 65 81 Zsp Zmd 45 35 75 70 Zsm Zfsc Zfsm Stratified rocks Intrusive rocks 16 Ont Ong Odt Qa 80 |Zmp Zcp Zcr* Zcma Zcm Zfcr |u |Zip |Zim 70 56 35 85 Qa |Zmg ^cmr 8 14 30 Qt Qa 16 Qa 24 Jdh 24 Jdg Qcf Jmtc Ylg Yp 13 6 J^tm 30 25 Qa 10 10 Jd S Qcc 22 9 13 37 55 30 Zmd 50 50 45 50 78 20 Ymc Yq 74 45 Zfsc Zfsc 28 D 38 |cw Jmt 51 M 30 Zfsm Ypg 15 70 57 Qt 25 J^cc 46 Zfcr 11 ^cbb 45 43 80 50 Jmm Jmmc 39 40 60 Qa 36 48 QTt Jd 35 7 10 6 Zcs Lower Cambrian 600 Ma Ont |s 80 |Zmp 15 Lower Ordovician CAMBRIAN |sql 54 60 Ont 70 65 80 47 84 |sq 20 70 |Zmm 80 Odt Middle Cambrian |squ 10 Ontr |Zu 50 Cu J^cc 24 Jd Jmhs Zcma 8 82 |s 75 75 70 70 40 Jd Ob 85 80 25 Jmh Zcp 35 61 68 Jd 45 45 Zmd 15 65 65 80 Qt 16 79 Odl |cwmq |Zo |Zlm Oq 60 45 60 |Zmg Ob Odm* 478±6 Ma Upper Cambrian |cwm 75 65 70 38 36 5 83 Ob |Zmg 25 28 ^cmr 70 55 |Zg ^cbb Qa Jdg 70 13 16 J^tm Jcm 48 15 65 Ong Oq 80 Qa Ob Lower Ordovician and Upper Cambrian |uq 30 15 |Zu 60 |Zu 80 Qa 45 85 72 64 Oq |Zu |Zu 48 85 Qa 72 74 85 10 15 |Zms Ont Ont 39 47 10 76 Ogp ? |um |chs |cw |Zl Fauquier Group Ont 65 ORDOVICIAN 52 70 64 Ogg 472±4 Ma Middle Ordovician Stratified rocks 35 53 65 |Zu Oq SUGARLOAF MOUNTAIN ANTICLINORIUM AND BUSH CREEK BELT |clp 80 |Zmg 60 Ob |frs |clc 60 Oq 50 52 |Zmbg 21 4 D D 20 35 60 6 Qt Jdc J^ccg 3 8 |Zu Ogh* |cwb 58 65 |Zu 88 58 64 45 Chilhowee Group |Zsd 80 Oq 85 60 70 70 71 Jd ^cmp Jd D |cw Yg 57 Yq 45 78 Yml 26 62 38 9 |cp 39 70 Qa 55 43 83 |tbh |ch Qa 83 ? ? |ca 73 60 60 78 70 |Zu 67 18 80 |t |s 55 70 84 |Zu 75 Stratified rocks |tf 58 |Zmg |Zmp 30 80 |tb 75 75 80 85 75 20 24 32 60 |Zu |Zu 57 50 72 80 |Zmg 78 80 |Zmbs 50 ? |td 75 67 |Zmg Upper Ordovician Ontr |wact 85 70 75 58 75 76 65 Qa Qa 55 83 12 25 ^cbb |Zmbq |Zmbg 5 QTt 20 Cu 17 Qcc Yg 35 J^tm Jdg 15 47 Ym 84 78 Ya 27 50 87 62 40 Jdc 27 48 60 Ygt Zmd Yp 50 75 Qa Zcp 60 Qa 60 68 85 40 Qa 10 65 15 58 Zss 5 15 Qcc Qcc Zcp Zcr 60 56 |cwb 55 20 35 20 28 Ypg 31 50 75 Yp ^cbb 80 |Zmbq QTt Qa 80 8 18 65 80 20 47 80 Yp 22 36 42 Zmd Zmd Ypg 15 70 Zcp 25 56 |chs 40 34 4 10 45 Qa Jd 52 54 Jd 20 55 Zcm Zmd 23 Qcf 10 |Zmbq 20 Qt 22 88 25 19 16 |cwb 34 65 60 35 25 Jd 45 Zcp 65 58 20 QTt 75 |wa 80 43 |Zmg 80 70 |Zmbq 35 73 21 55 81 60 Qt Jdh Qcc Yg 25 35 20 Yg Ylg Jd Ymc Yq 15 45 38 Qcc 15 47 70 Zcm 27 46 Yp ^cbl 82 QTt Qt 16 15 Ym 10 32 78 25 Qcc Zcma 50 53 Zmd Ylg 74 15 35 Jd QTt 80 80 Qa 15 ^cbb 67 64 Qa |Zmbq 24 14 78 70 70 Ql Qt 45 35 40 Ygt 30 52 Zcp Yg |Zmbb 15 20 20 |Zmbq |wac |Zmg 80 DEVONIAN |ar Qa Qa |Zu Upper Devonian |war 75 81 |Zmbq 42 Qa 63 60 45 Onu |cs |e 55 Ob Ob |Zmg |Zmm 53 50 32 Qa |Zmbq 5 QTt 25 28 43 70 Zcr 6 86 36 16 10 68 |t |ca |cwb 66 |cwm 30 65 25 42 80 80 67 ^cmr Jd 62 70 64 80 Ong 362±3 Ma |fa |cwo 70 75 |Zmbq 73 83 QTt 30 Zss 47 Zcs Qa 36 48 62 36 15 20 Yp 35 72 M 46 M 40 34 Qcc Jd Zsm Zcm 35 Yp 30 Qcc 60 Qcc 62 40 70 88 46 Qa 12 Ql 13 Ql 80 80 5 |Zsb 88 25 27 20 43 56 Ypg Yp Zss 47 Ym ^cmp QTt Zsp 30 Qa QTt |Zmbq 78 |Zmbq |Zsmp 55 70 |f |fr 82 Qa 85 Qa 67 85 72 65 80 5 61 42 Jd 62 81 84 Ql 18 Zcp Zsm Zmd 25 Zss 53 Yp 35 45 |chs 45 35 58 46 Jd 16 Jd 18 82 77 44 10 ^cbl 29 28 45 31 86 20 44 56 15 |t QTt |wact Ylg 31 53 5 Yc 50 70 QTt 32 58 40 34 80 2 20 ^cmp ^cbb 17 Qa Qcc Yp QTt 11 10 Qa Qa 63 Qa 78 O|gl |cb 43 65 73 8 C O|gu 72 37 Qa 80 Stratified rocks 78 |Zmm 80 54 Jd 85 T UL FA |Zmp 61 80 Jd 67 78 72 82 74 88 52 Jd 26 Qcc Zcs Zss 37 Zcp Qa 65 23 10 20 22 80 30 18 |wac Qt Qcc Qt Qcc Zcr 52 34 85 Zcp Ygt Yc Yc Yp 25 Qa QTt Qa Qt 75 85 |Zmp |Zmg 75 Obs O|c 30 |Zu Ont* Obrr |t 85 75 87 83 86 75 |uq 12 27 22 17 53 Qa Ybg ^cbl QTt |ca Zcp 64 33 Zmd 31 Yp 58 33 35 21 64 10 QTt 10 Qcf Zcs Zmd 35 Ya 27 70 10 55 26 QTt 73 Qt 8 20 Qt ^cbl 25 53 22 Qt Jd |u 80 12 |Zsq Oq TRIASSIC Intrusive rocks 449±7 Ma Obss Qa 87 67 |Zsmp 68 17 12 70 40 68 Qa 72 45 80 Beekmantown Group 65 65 Qa 70 |Zib |Ziq 58 85 |Zmbq 84 |Zms 44 ^cmr Dg* FREDERICK VALLEY SYNCLINORIUM A' 74 78 |Zmbq 84 77 |Zmbq |Zu 78 80 73 Qa |Zg 75 |Zip 47 35 82 20 POTOMAC TERRANE ^cmp Obps |Zmp |Zu 46 44 |Zmbq 29 52 ^cmr QTt 85 84 72 Jd Ql 21 S S 26 32 42 72 15 |Ziq 50 32 |uq 31 QTt 8 ^cbb 30 10 75 Qa 12 16 48 23 36 82 Qt |squ 12 25 20 Jd ^cmp QTt 33 Qcc Zcm Ybg Zmd Zcp 34 Ym Zmd Ygt 27 10 42 44 |squ59 40 ^cbl Ok* |Zmp |Zu |Zmg 75 ^cbb |fl 60 75 |Zmbq J^ccg 463±8 Ma 67 80 70 87 80 83 65 83 80 |Zsb 74 71 78 67 32 16 75 82 82 |Zib 58 78 50 68 66 77 65 70 Qa 52 75 74 80 |Zmbq 79 25 |Zmbs ^cbg J^cc Osnr 50 75 67 60 |Zsq 30 80 81 30 72 47 30 16 73 78 38 60 |Zmbq Upper Triassic J^tm Om |Zms 80 20 75 Jmm Oc 57 70 |Zsmp |Zsq |Zss 20 52 53 35 |u 45 |sqm Qcc S 12 |ca |cp |ch Yg 49 Jd Zmd 80 Qa 28 17 Qcc |cwb Zsm 65 Yhm Ya Zss 20 41 |tbh 80 85 65 50 31 25 32 5 Zcp 10 30 32 Zss Yg Ya Yp 35 S |Zil Qa 12 30 |Zib21 Jd Qcf 72 12 25 QTt 13 60 30 50 64 40 Qt 86 12 86 77 QTt 75 14 Jd 65 40 79 72 50 36 Zss 62 42 20 36 42 10 |cwb 20 24 46 32 77 QTt Qcc |Zmbq Jmmc 86 55 54 JURASSIC 201.2 201.2 ±1.3 Ma ±1.3 Ma Stratified rocks Qa 78 82 55 51 |Zmbq 44 |um |squ |uq 50 48 |Zsb 52 Sl 44 55 30 50 52 Qt 17 |ca |cp 25 42 Zss 30 3 26 38 Zmd Ya Zmd 20 |clp 54 57 L 86 QTt 43 28 35 26 |cwm |td 55 |tb |tf |wact |war 80 30 80 Qt 15 Zcr 29 20 10 30 Yp 30 80 40 34 Zcma Ybg 35 45 Yp 45 Zrd 25 22 65 Ygt Qcc 8 16 QTt Qa 78 25 27 86 20 55 36 45 50 70 Qcc 23 30 60 Zsp 20 25 35 30 Yp 10 Qcf ^cbl 15 Qcc 89 45 36 30 |sql 46 |Ziq |Zib |uq 78 82 14 Jd 67 70 81 84 49 60 25 30 |um |ar |fr Qa 20 |um 70 |Zmg 87 78 81 72 50 12 Lower Jurassic Jdg* GREAT VALLEY SECTION 85 89 80 70 65 80 10 45 50 29 83 81 40 75 45 34 76 73 60 80 72 |Zip 33 45 43 35 ^cmr 80 25 15 34 11 68 S 44 42 Qcc 50 48 28 60 21 40 60 75 20 |uq 32 |um Jd 45 |squ 58 68 15 |um 32 65 64 Jd F |Zil Qa |frs QTt 16 70 53 Zsm 70 22 Qcc 15 Zcr 16 29 33 52 Yp Ya Jd Yhm 45 Zss Zsm 67 35 65 25 Zmd |cwb Qcc 48 Zss Zcr Zcp 11 67 |wac 15 Zcr 22 57 F 35 15 56 Qa 10 Jd Yg Zmd 26 Jd 28 50 Ya 22 32 75 13 25 34 |uq 60 12 80 |uq 60 35 52 70 |Zmbq |Zp 5 12 54 85 15 83 80 |Zmbq 78 |Zsb |Zsf 52 39 75 CRETACEOUS Dp 75 60 75 83 |Zsb 48 62 74 60 80 31 74 |Zsq 28 |Zss 62 |Zim 70 56 84 35 42 Qt 20 85 72 |frs 32 10 F 27 62 |f FF F 88 Jd Ygt 42 45 Zcr 45 17 18 Zn 40 QTt 45 80 12 25 17 5 17 15 70 |t 25 55 26 30 70 67 QTt 45 18 20 26 58 42 40 67 L 39 L F Qcc Zcma Yp 50 |t 68 |clp 28 78 QTt F |ca 39 67 F |ar 82 37 82 Jd 40 |Zib 62 Jd 84 |frs |fr 11 33 30 |ar |Zsq 10 53 |Zip |fr 75 Qr |u 60 75 50 72 83 42 62 82 60 60 25 6 |fr 27 ^cmp |cwb 58 45 Jd 49 Jd Ya Yqp Yp 78 F 19 30 |uq 65 |Zss |Zsq 40 |Zsc |Zsq 45 |Zsb 42 40 47 |Zsc |Zip |Ziq |Zss 45 |Zsq 38 56 Sl |u 53 60 15 82 75 |Zmbq 28 72 61 |Zsq 45 69 46 41 30 40 80 75 70 |fa 72 Jd Sl Qt Qt QTt 57 21 ^cmt 22 35 23 Jd Zsm 32 41 F L |tbh 23 |wac 24 22 6 F L 60 64 Zcr Yqp 23 44 Zmd Zcm Zcr 25 Qr 25 36 30 80 16 Zmd |cwb 30 24 70 45 L 75 |war 28 50 50 82 |wact Yc Jd 20 45 46 38 15 |tf 2 36 45 12 16 Qcc 73 L 35 34 77 66 50 60 52 56 36 Zcr Yg |clp 89 Qa Ybg 29 50 12 56 F 78 O|gl 21 60 45 85 75 68 51 78 Sl Sl |um Jd 17 75 55 |fr QTt Qr 55 30 76 Qcc 37 Yg 30 42 28 75 88 |td F |tb 40 60 Yhm 19 Zmd 25 |cwm |cwo |ch 32 Qt 24 21 Zmd 58 7 Qr 62 50 46 77 27 53 48 85 25 44 35 Ybg Qa 7 |frs QTt 75 |ar 78 |fl Jd 11 |t |ca 60 Ybg 40 Jd Zss Zcr Qa 21 14 15 20 18 35 32 |ch 51 |cwm |t QTt 80 35 QTt 16 24 55 40 F F F 10 56 74 65 82 QTt 45 |e 29 55 Qa 25 50 36 60 |fr 57 Qcc 65 QTt Yg 18 66 36 50 |clp 30 87 33 5 63 83 70 B |ca 36 50 75 70 60 62 73 70 Zcma QTt Qt 32 |frs 17 |ch QTt 37 44 32 62 ^cbl Qa Yqp Yp 32 Zcp 35 |cwb 78 20 47 20 20 67 26 30 20 Yqp 60 Zss Yg 60 Yp Zmd 48 |clc Qcc 85 21 22 Zrd 62 55 50 29 10 QTt 86 30 Zmd 32 36 15 |cb 33 56 |cwb |cwm QTt |tf |tbh 62 Oc 53 |ca |wac 50 35 58 88 35 Obss L |wact 28 67 Obs 33 56 44 20 46 Ybg 40 QTt QTt Ybg53 47 28 ^cmt Qcf |cwb Zmd 37 Jd |cwb50 Zrd Zcp Zss Qcc Yqp 41 32 52 56 Ygt 35 56 Zss |clp |clc Qa Jd Jd 36 58 |ch 68 |ch Yp Qa |tb 15 50 Osnr L 25 58 Obs 10 Qcc 70 20 Qa 10 |cwo 36 20 32 Ygt Qt 36 66 Qt L 81 66 ^cmp 11 60 Zrd Zrd 12 Qcc |clp Yml Qt 49 27 47 45 45 Ya Jd M 25 70 26 17 50 Zcr 40Yp 15 |war O|c 62 40 43 QTt 5 71 70 32 28 42 Obss 72 Oc Oc Obrr 23 Ybg Ya 70 5 45 Jd 50 13 77 73 47 31 Yml Zmd |cwm |cwo 2 42 35 30 Qr Jd |ca |t 11 82 82 21 BRIN KLOW T HRUS T FAUL T 65 53 54 55 38 35 53 47 20 47 45 81 |ch 45 Qcc |cwb Yhm 22 Zcm L 61 53 72 |um 53 11 75 M |Zsmp 85 82 74 Jmhs ^cmt UL 35 21 59 Qt 22 32 50 |chs Qcc 45 80 |ar 75 71 48 42 20 78 75 57 |Zsm |uq |Zim |Zic |Zip 74 M |Zsb Chatham Group ZO NE 13 38 Obrr 36 25 25 54 Zmd Jd Yqp 61 F |frs 76 32 25 Lower Cretaceous Jcm 80 52 80 F 88 MILLS 30 L 65 Om 45 85 25 |ca Zcp 34 42 23 41 5 QTt |fr 75 87 56 50 |Zsl 32 83 50 ND 71 |e 38 16 26 F 23 35 18 25 Yg |fa |fr |frs Qa SH EA R 59 Obss L 70 Ygt 51 12 Qcf Yg Ygt 80 4 72 |Zstp 62 |Ziq 86 |Zsq |Ziq |uq 36 Newark Supergroup 79 86 BU Obps 30 60 43 L 22 Qcc 47 Qt 55 80 34 Ql 22 24 Qt 42 Qa Kps Jmt Jmh 67 Jdh* Jdc 200 Ma Jmss Jmtc Meriden Group 36 PLU MM ER S IS LA Obs 22 41 51 Osnr 80 10 62 Yhm Ybg 40 37 42 |fa 22 11 16 Zcr Qr 22 Sl 10 77 |Zpq 85 10 CR EE K 72 25 Om Oc 35 45 37 45 78 |cwb Qa 54 30 36 Zcm Zcp 20 35 67 86 85 69 15 ROCK 21 53 |ch |tf 22 55 41 30 83 6 3 25 67 Qa O|gl O|gu 55 78 86 50 LT 42 Zcp Qt 49 32 Jd 30 36 20 5 27 35 32 |ar 82 15 53 52 85 55 F 67 7 76 25 45 FA U Qt 31 3 Ygt 78 30 33 Zss 67 32 32 |t 89 78 42 88 15 Jms 70 50 82 70 83 70 82 |Zsl |Zsb 18 |Zsm M 45 M Qa Jd* Stratified rocks 55 85 65 VE Oc 66 85 77 15 |tbh |td |tb 5 83 Zrd Yp Yqp Ybg Zcp 73 50 M M M 50 82 19 Jd 40 60 M 81 CULPEPER AND GETTYSBURG BASINS Unconformity |Zpb 85 81 RO O|c 80 |wact F |chs 74 80 32 43 74 62 20 33 |Zim 68 40 73 70 43 L |Zmbq 55 |Zmbs 25 COASTAL PLAIN PROVINCE PIEDMONT PROVINCE |Zmbq 63 QUATERNARY Pleistocene Intrusive rocks 85 82 L |Zsm Qa 26 70 Ql Tertiary BLUE RIDGE PROVINCE 73 Qa G Oc 50 67 L 72 22 32 20 19 F 48 77 81 53 27 75 79 L 48 82 36 67 85 83 |Zmbq L |Zsl |Zsb |Zsm 40 |Zsq 40 78 59 47 55 L 80 6 71 |Zmbq VALLEY AND RIDGE PROVINCE 65 |Zmbq T 30 71 68 58 |war L 50 |cb 77 Qcc 21 57 26 Yp Qa Zmd 82 33 43 Jd 60 62 |Zstp |Zsq 16 36 M 30 Cu, Au,Ag 50 35 42 32 Qa 85 68 77 15 83 N 34 63 Qt 68 57 36 57 32 Ya 31 ^cbl 44 75 34 55 55 60 |Zsqp 82 52 43 19 65 73 45 |fl 62 Qa 81 32 32 37 35 80 50 |Zsq 47 80 80 88 Qr Qcc QTt |Zmbq 72 Qcf Qt 67 |Zmbq Holocene 80 80 58 |Zsm 77 50 |Zsm 25 35 25 60 20 62 |Zshp 49 |Zsb 45 38 82 63 86 |Zmbq 34 12 72 Qa 18 SA 50 70 L 75 |ca L Zss Jd 41 Qr 50 60 47 |Zil 80 25 62 |Zshp 78 UNCONSOLIDATED SURFICIAL MATERIALS 46 33 |Zpb 80 |Zmbq 32 Qr 74 M 63 |Zpb EA 15 38 49 Oc 20 41 O|c 9 70 L 41 41 ^cmt 60 Qr L 35 40 Qa 55 68 77 71 56 M M Qa 30 58 78 PL 85 34 Qcc 44 32 39 L 22 37 31 ^cmp 43 78 |fr O|gl 47 35 33 75 Zcr 43 23 61 77 81 65 45 42 23 Zmd 24 Zmd 34 |Zstp 57 74 28 54 72 86 |fa 21 |ca |fl 82 |Zsq 44 81 45 74 34 49 Zcp ^cmt 52 52 73 55 ISLA ND F AULT 50 |wac 15 73 Ygt Yp 31 Yqp 21 |ch Qa Zsm 35 30 50 Zss Zcm Qcc Zmd Yg 40 |fr 55 |fa Qr Jd |frs 72 82 40 Qt |Zp 65 PLU MM ERS 15 38 35 L Obss |chs 30 39 35 Zcp Zss 17 Jd Qcc 70 Zmd 31 Qt 43 38 |Zsm 22 60 |Zsq |Zw (Units with an asterisk have been dated) 28 Jd Jd 86 |Zsl 68 28 70 76 3 Qcf 81 82 46 55 68 |Zsmp |Zsb 64 |Zsl 67 F F 52 FA UL T 80 86 75 Yhm Ygt 23 23 18 65 52 2 86 40 Zss Zmd Ya Ya Yq Ygt 16 19 46 Au QTt 30 52 L 81 70 65 80 32 30 30 70 60 Qa 5 80 CORRELATION OF MAP UNITS 37 |Zp |Zsq M 86 |Zsq 25 86 46 66 |Zicm |Zip 47 |fr 32 72 36 82 20 37 62 28 35 F 86 80 83 |Zsb |Zsm |Zsb |Zsm 85 M |Zsb E Qt Qa 38 20 28 30 81 Yqp Yqp 30 Zcp 73 43 Zsm 30 22 85 |cwo Qcc 31 45 33 Jd 35 69 72 26 3 Qt |Zsq OV 88 68 L Obs 40 8 |tbh 77 Obs 80 47 31 |cwb |clp Zrd 74 Zsm Qa Zmd Qcc 32 Jd |Zicp |Zsb Cu Cu,Ag 54 58 Pb 86 75 |Zsb Qa |Zsmp 75 44 GR 80 |cwb 21 29 Yp Yqp Qa 63 Zrd 35 81 52 10 56 Jd 35 83 63 |Zstp 58 |Zstp |Zsm NT Obss 40 19 42 Zmd Ybg 28 32 Zcr Zcr 83 Zss Jd |cwb |clc 44 29 Qa 40 33 40 Zss 22 |tb |tbh 78 8 47 38 Om 73 28 Zcr 49 38 QTt 20 Zcm 42 Zss 52 35 21 82 42 30 |Zsm |Zicm Qa 36 75 48 SA Oc Osnr 23 7 Zcm 10 Qcc Qcc |cwo 46 79 |cwo 73 |clc ^cmp 46 Qa 32 |ar |fr 85 42 85 50 47 29 70 72 EA 12 Obss |tf 25 38 40 41 35 50 30 |Zsq 29 82 40 FA UL T 63 79 Qa 13 20 |ch |cwm QTt 54 82 |frs Qr 38 70 Zsm Zss Zsm 33 Jd Qa Yg 33 Zsm Zsm 27 35 Zrd L Qr Qt 31 25 73 14 11 8 43 25 20 61 47 Qcc 24 44 |ca |ch 31 |clp 38 Zcr O|gu 63 52 62 Qr 35 33 Jd Zcp Qa 21 Qcc Zss |fa |fl 87 PL Qa Obs |e 8 30 30 |fr 37 ^cmp 32 39 Qr 47 F RU ST Obrr 30 18 |td Zsm 35 Qcf 86 O|gl |Zsmp Cu,Zn |Zsb |Zsm |Zsb |Zsm |Zsq TH Oc |td QTt |cb 65 79 20 20 40 23 QTt 65 80 40 Qt 80 L 47 40 85 50 42 22 4 Zss 36 Zcp 18 16 |cwmq 38 26 15 |cwb Qa 38 34 Zcr QTt ^cmt 50 RU NM 25 54 Obps QTt Qt L 18 Zcm 34 21 |clc 25 35 Qcc |cwo |fl BA RN ES VIL LE -M ON RO VIA THR UST FAULT HY AT TS TO W N 51 Qa 50 |e 24 33 Osnr Obps Obrr Oc 78 38 |cwm 17 Zcr 35 Zcp Jd Zcp 47 |ch Zcp Zmd Zcr 15 68 Qa 20 12 23 32 |cwm |war |tb |tf |wac 15 21 58 62 28 |cwo Qcc 20 22 37 BU LL Obs 7 |chs Qcc Zcr 24 LT Obs 35 41 |tbh |ca Qcc Zcr Qa Zcp 19 2 27 37 22 4 67 |ch 30 Qcc Zcp |clp Zcp Zcr |cwb 70 Qcc 59 20 46 45 Qcc 12 33 85 O|c 33 57 51 60 Obrr |cb 62 25 5 |wact 60 82 QTt 20 43 32 FAU L Obss 69 Oc L 50 48 Oc L L 40 75 27 60 83 60 8 45 37 51 34 45 |tb |td 4 15 26 57 |cwb |cwm 37 25 Zcp Zcp TA IN L Osnr Obss Oc 45 Qt 57 Qa 32 37 51 20 Qcc 38 Zcp 52 UN 30 Obps Obrr 35 25 62 |tf F 13 85 Obs 42 Qt 72 Qa 52 47 Obps Obrr 66 QTt 23 62 L 28 21 56 L 49 Oc 63 60 Om 34 29 F |e |war |td 35 18 MO 30 QTt Obss Obss 52 Obps Osnr Oc 60 30 Qa |tbh |tf 65 |tb |cwb |clc N 60 L 50 O|c Qt 77 60 40 Obs Qa 50 Obps 67 O|c 15 |cwo RU |cb |e O|c QTt 12 86 55 27 L 89 Qa QTt |tf |tb |Zshp |cs |ar 72 37 12 BUL 35 Obs Qa 70 23 12 80 FAUL T Osnr Oc Obps |e Om 78 55 70 Qa 58 67 KEE DYS VILL E 27 80 LT Obrr 65 Osnr HI LL 78 28 82 60 20 QTt FAU 80 22 RT |cb 35 L SHO A |e SIM 2889 Explanatory pamphlet accompanies map 1 1 4 U.S. Geological Survey, Reston, Va. 2Maryland Geological Survey, Baltimore, Md. 3U.S. Geological Survey, Retired. 4Deceased. 1 2007 1 1 3 This map is available for sale by U.S. Geological Survey, Information Services, Box 25286, Denver Federal Center, Denver, CO 80225 For product and ordering information: World Wide Web: http://www.usgs.gov; Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government Printed on recycled paper
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