re 39. 6S /¥: But 62 Bulletin No. 62 February 3, 1923. M. M. LEIGHTO™ COMMONWEALTH OF PENNSYLVANIA DEPARTMENT OF INTERNAL AFFAIRS James F, Woodward, Secretary gt a ne ce en nt ag ee ae, BUREAU OF TOPOGRAPHIC AND GEOLOGICAL SURVEY George H. Ashley, State Geologist co te (eee ee ee eee = ate ey —— ROCKS OF THE McCALLS FERRY QUADRANGLE, PENNA. By Anna I. Jonas Invroduction, The McCalls Ferry quadrangle lies be ween Lancaster and Peach Botton. Susquehanna River, which’crosses the quadrangle from the morthnwest to the southeast corner, divides it almos equally between York and Lancaster counvies, The geologic mapping of the area was done in cooperation between the United States Geological Survey and the Topographic and Geological Survey of Pennsylvania and represents the joint work of Eleanora Bliss Knopr and Anna I, Jonas, Drainage » The quadrangle lies within the upland plateau region of south- eastern Pennsylvania, The most conspicuous feature of the area is the Susquehanna Hiver. t flows southcastward in a rocky gorge cut to a depth of several hundred fcet below the surrounding upland Surface. Since the days of the Indian the river has. been used as a 9 highway of travel. In the 19th century the York County Tidewater Canal was a busy artery of transportation but after the building of the Columbia and Port Desosit branch of the Pennsylvania Railroad on the Lancaster County side, the canal fell into disuse, The Susquehanna is a turbulent river that flows for the most i, part in a rocky channel occupying about one-fourth of the width of Hee iy the river's bed. The fall is 120 feet in 23 miles across this area, an average fall of 5,2 feet to the mile. Some of the water powcr of the river was harnassed in:1905 when the dam and hydroelectric plant was built at McCalls Ferry, 23 miles above tidewater. From this plant, which has’8 main generator units with a total capacity of 86,000 kilowatts, the Pennsylvania Water and Power Company supplies electricity to the cities of Lancaster, Pennsylvania, and Baltimore, Maryland, and Edgewater Proving Grounds, Maryland. The most important tributaries of the Suscuehanna are Conestoga, Pequea and Mudéy Creeks on the Lancaster County side, Fishing, Otter and Muddy Creeks on the York County side. The Rocks. The rocks of this area were deposited as sediments in bodics of water, Material derived from the wearing away of a land surface was carried by the rivers in suspension or solution and deposited in the Sea either ag gravel, sand, silt or limy mud. Later it was consoli- dated and hardened by pressure of the overlying beds and by heat from the interior of the earth. Had the processes of change stopped at this point the resultant rocks would have been arkose, sandstone, Shale and limestone, But the rocks have undergone various alterations that resulted in the complete recrystallization of the original mineral constituents and the formation of textures that are different from those of the original sediments, Such recrystallized rocks are known as schists. A schist is a metamorphic rock possessing a foliated structure that causes it to split readily along planes approximately parallel, The rocks of this area are, for the most part, crystalline schists, . The oldest rocks in this region are the Wissahickon schist and the Peters Creek quartzite and schist. They belong to one of the oldest eras of geological history, the pre-Cambrian, The Wissahickon schist of this area is the northern phase of the Wissahickon mica- eneiss of the Fhiladelphia region. It is typically developed in the Tucquan anticline which crosses Susquehanna River at Tucquan, The Peters Creek formation was named by Eleanora Bliss Knopf and the writer because of typical exposures along Peters Creek, a trivutary to the Suscuehanna River near Peach Bottom Station, Lancaster County. The Wissahickon schist is an albitc-chlorite schist or gneiss interbedded with layers of chlorite-or muscovite-quartz schist. Other minerals usually present are calcite, epidote, garnet and magnetite, The Peters Creek formation consists of a quartzite and a chloritic Or sericitic schist. The quartzite is a white to light greenish gray, crystalline rock with some feldspar and muscovite. The schist is made up of bands of granular quartz between layers of sericite and Clinochlore, Masnetite is usually present, These schists are several thousand fcet thick and are widely exposed over the south half and much of the north half of the McCalls Ferry quadrangle, In the northerm part of the area are rocks which belong to younger geological periods, the Cambrian and-Ordovician, The Cambrian rocks were deposited on an old, smoothed-off, crosional surface of pre-Cambrian rocks. The oldest Cambrian rock exposed in this area is mt Hit ¢ , poh AS , ee es uv s : ny Ae ® | * _ by ‘ J ) , \ ~~ 4 , ‘ : \ , , ri > } t 5 Hit ‘ vu ( ¥ a beet Pi Uy ih t in 44 ‘ : , ; iy Ne j F ¢ fitany ; } t Wh fi the Harpers albite schist, It is alight to Gark gray fine-grained rock composed of biotite, muscovite, quartz, albite and some calcite. Tourmaline needles are of frequent occurrenec, Towards its top the Harpers schist becomes more cuartzose aud calcareous and passes into the Antictam albite schist, the metamorphosed representative of Antietam sandstone. The Antictam calcareous schist grades upward into the gray Vintage dolomite. This dolomite or magnesian limestone is the basel member of the lower Cambrian limestone serics widely exposed north of the McCalls Ferry qurdrangle. The dolomite is granular, massive, blue to gray, cond weathers chrlky white. Some beds are thinner 2nd contain caltnreous blebs thot werther in relief. Crystalline limestone (marble) and black slate and limestone conglomerate overlie the Vintage dolomite. -The limestone is blue and Sparkling, with finer grained dense dark blue beds usually gashed with white calcite veins, ‘The black slate forms partings and thicker beds in the marble series, In some places mica has been developed on the partings, Pyrite is commonly present in crystals, sometimes in veins. This blue limestone series is Ordovician and mucn younger geologically than the Vintage dolomite beneath it, The rocks so far deseribed originated as sediments, Rocks known as igneous because they were once in a molten condition also occur in the area, The molten material cane up from lower down in the earth and fillec fissures in-the rocks. These fissure fillings are called dikes, In York County, near Peach Bottom, there is a small exposure of a dike rock called serpentine or soapstone. It is a crystalline schist which has been developed from an original magnesian silicate rock of igneous origin. The rock is light green to cream colored, sort with soapy feel and made‘’up laigely of the inineral steatite. Naturally the seryentine dike, ‘which represents the injection of molten material into a fissure, is younger than the Peters Creek SChist into which it is intruced, A more prominent and extensive dike cuts the rocks of this ares for 18 miles in a southwesterly direction from the‘nortiern e¢ge of the quadrangle through Rockhill on Conestoga Creek, through Pleasant Grove and Muddy Creek Torks. The rock of this dike is diabase, popularly known as trap, It weathers into round yellow-coated bowlders that strew the surface alone the course of the dixe, Diabase is @ grayish black crystalline rock composed of snarkling small laths of feldspar and black augite. It is the only rock of the region that has not been altered since it hardened, and is the voungest rock of De ares tor it cuts all the others, It is an offshoot of the great outpouring of Triassic lava that forms the Palisades of New York and New Jersey and crors out in many »vlaces in eastern Pennsylvania, Structure, When the rocks of this area were laid down on the sea bottoin as seciments they were in nearly horizontal beds, one layer above another, They were buried to a great depth by other seciments and while 50 buried were compressed vertically by weight of rock cover, and were subjected also to a lateral pressure acting on them from the southeast, SE ae a is ‘ le nN yew’ ey Wily? Y D ay! > the direction of the Atlantic Ocean. As a result of the pressure the rocks were throvm into a seyies of »varallel arches and troughs, and lifted above sea level, #rosion acting uoon the rocks has removed the covers of the arches and troughs, that we call anticlines and syn- clines, and has produced the irregular surface distribution of the rocks as we now see them. The linear direction in which the rocks trend is called the strike. In this area the rocks strixe for the most part southwest. In the valiey to the north the older rocks, the Harpers and Antietam schists, form hills that rise above the general level. The hills are anticlines and the intervening valleys of crystalline limestone are synclines. The Tucquan anticline with its axis at Tucquan is a large arch whose flanks are crumpled into smaller anticlines and synclines and these again are wrinkled until the smallest folds are of dimensions seen in the hanc specimen. The ’ Peters Creek syncline is south of the Tucouan anticline, and, like it, is composed of numerous minor folds. tlateral pressure not only bends rocks into arches and troughs but may incline these folds to the point of overturning, The rocks may give way under the strain and break as well as bend. As the result of continued lateral pressure blocks of rocks or parts of the. earth's crust may be pushed over other blocks or parts, for short distances or for many miles. Such a break is called a thrust fault and the plane along which the rocks move is called the thrust plane. A thrust fault of considerable extent occurs in this area, ‘The pre-Cambrian Wissahickon schist has been pushed from the southeast over the Cambrian and Ordovician rocks of the limestone valley. ‘The trace of the fault plane on the surface is the sinuous northern boundary of the Wissahickon formation. North of this line the rocks that composed the overthrust-block have been removed by erosion. As erosion continues more of the overlying schist block will be removed and a greater extent of valley rocks will be uncovered, The McCalls Ferry quadrangle exhibits two areas fairly distinct topographically, a broad valley country between ‘Jashingtonboro and Willow Street, and a dissected upland in the rest of the quadrangle. Difference in solubility and hardness of the underlying rocks accounts for these features. The broad valley country is vnderlain by dolomite and crystalline limestone, rocks that aye more readily Soluble and not so harc as those in the rest of the tuadrangle. The general level of the higher hills in this broad valley is atout 400 feet above sea level, ‘The sand hills that rise above the general level of the valley in Conestoga and Pequea tommships are vncerlain by the harder Antietam and Harpers schists. South of this limestone valley is a broad, well dissected upland, The hills in any part of this upland rise to a general level, buta Study of the topogradhic may shows that if the valleys were filled the general surface would be 3 wpm plain rising from an altituce of about 600 feet along the south side of the limestone valley to 800-900 feet‘along the Tucquan anticline, or from Brogveville to Rawlinsville, and thence sloping gently to the southeast. Near Peach Bottom the upland is 400-450 feet above sea or about the same as in the limestone valley at Willow Street. Sy ek ; i , 4 Ch At | iia ° ai i *) ji m3 \ ; \ ” if ’ ‘ - | als ® yo ne 1) i ed 4 ye a Wp) Gea ab a ‘ q alee a es | } \ ' Ty nes t * ~ s ' an te say i ) iv? 1 ai ‘ F \ if re. ee. 4 . MS ata vt ‘ , r va * > ! ‘ / we 4 . as myn i . o ‘ 4 y vA _ ' N ) Py ( it 5 j \; i | e iv 7 i" ’ i i - ’ 4 1 ‘ \ ‘ ‘ | af ~ is \ x Af yf ‘ i 4 ce iat } ts ee ‘ ‘ i & b { rt" ‘ ; i ‘ i 14 = H . ( ‘ f ‘ 2g \ , Wh H 4 nr f . = ‘ ¢ , ea x r t vf j 5 4 ul ‘ ' i y help 4 F ‘ j : i Dh i ys 1 f ; i 4 7 * \ hy , aie rar - Pad af 1 i * ’ + 4 ) t \ “% 4 # ’ . 7 sf s - h 4 ’ . i 2) tae ‘ 1 i ‘ , ; 1 ’ ; j ~ ‘ Roemer ice Me hie J y 4 f yy Vu ee at \ 2% } ba Ps 1 py on 1.0% 1 ~ 2 + “ ¢ 4 vole : 1 * 4 v a. vo ee Nb Ny 1a y ‘ he th ' rs ty \ u 7 : - tou Ft + } hy , ( 4% Wy I eA ty ie ‘ er) woes r ~ * ‘ S s ‘ mae oft es 7 : eae wi ” ee ts + 4 j ,, 7 . 4 . a i } 7 } me ‘ wae v y “ ' t 4 ; ‘ 4 “ t Ms: a i xi ' va ree ioe ype Ls ; ’ a Ede , &® ‘ “ ‘ j Hi 3 ah of i » b ” : , a4 , i] oe YM % ‘ J , 4 i q we Mi t by A rr 4 k omy se) let ’ sg beste ue (aa a ey pny OT ae ANA Mea ba ~ eit i (re Bt : abe Pies a oy, { 5 + oe be MT Are adage: Mee & et en Sa Li Onee nah Eph i dale ‘ LJ i rs f 4 ’ a? a ae, ae Fs bo Wael ' ' Af i ee ih py hee) ‘ ey | ei? Se Wl ‘ Pony an tere i Ye ‘ Vice jag ral tt ay : Se hs Wh oily a Wh oF, This upland has been caused by the »resence of the ‘Yissahiclon and Peters Creek schists that art hard, compact, and not readily Soluble. The offect of erosion has been imuch slower on these schists than on tne limestone, and the difference in elevation between the plateau anc the valley is explained by the cifference in resistance of the underlying rocks. susquehania River flows southeastward across the trend of the rocks which'is northeast anc southwest. Streams that have lons been flowing over certain formations are influenced in their courses by the rélative position of yielcing ane resistant rocks, The accepted explanation for the lack of adjustment of Susauehanna River to the trend or strike of the rocks across which it flows is as follows: the river established its present course when the surface of this region was almost a plane that sloped gently to the southeast. This plane bevelled the rock structures ana the river course was determined by its slope. Consequentiy it now flows directiy across rock folds and overthrusts. Difference in hardness of the rocks across which it flows has determinec the width of the Suscuehanna River bed. It is widest near Washingtonboro where the valley is cut in soluble limestone, Through the Wissahickon schist, the harcest and most resistant of the rocks, the channel is narrow, and the valley sides are steeper. °1 The narrows below York Furnace and Tucquan have caused ice jams and high floods, The river widens again below Fites Eddy where it is eutting through the Peters Creex formation which is harder than limestone but not so resistant as the Wissahickon schist. Economic Peatures. Limestone, - The blue crystalline limestone belt in the northern part of the area contains valuable stone that might have a wide range of uses, as for building stone, ballast and road metal and for making dime and cement, Several quarries have been opened in the northern part of the quadrangle and the stone is used locally, but practical features restrict the development of the industry. In former years much lime was bummed locally for agricultural purposes. Old kilns still can be seen and are occasionaliy used in burning such lime as the neighborhood requires, At present the manufactured ‘oroduct can be bought so cheaply that burning of lime on the farm has declinec. Silver, - Along Silver Mine Run just north of Bumt Mills there is an old abandoned silver mine. ‘Work was begun 125 years ago and 4 shaft sunk, connecting with a’tunnel 400 feet into the hill. The ore, Which is argentiferous galena, occurs in a quartz vein in marble, it is revorted that lenses of ore the size of a barrel were found but they Soon pinched out and no large ore body was discovered. i wi forth Por aa: Pura | uly ah ey Oe He) ea hay 8 4 Wit & pmet Gage ate ta ad at he kote yj a aL) . 4 ‘ , ; r ves tive We } ~ edie) Be Re NVR ATL SS eS uf \ Dae, | Dit : ’ ¥ f Xt eiv's ¥ iT c Li |) ear t : a) t j e } ' Wha q i aif ¥ 4 5 i ' i | { . 5 PY’ / : \ ‘ i ¥ i , ' } / 4\ vy ‘ j ‘ - ay ? A 4 } M , ‘ \ ‘ fi 4 \ ¥ yar } : nh) \ mich ty ) ‘ AUT } " ( 4 ‘ ' 5 { ? [Pay « \ 4 ‘ , " : ey : \ ‘i { i , ack } fj ' { ‘ \ { ; i - : Pa) r tl . ey : i \) 4 4 i 4 . t 4 . \ ; ‘ \ , 4“ I ; " ‘ ‘ i } > Py vi 1 { j { j . ; ( / ( 48 if . - f i ~~ ' t fj ‘| " \ { ye ‘ eee ; } ‘ ’ ~- } ny vif > j t , i , & \ { 1 { - : i sod Li i H| ba f , { . : { 2 ee { ; } + ry ¢ aa “ i ’ j i Pyra Wana "4% ' r f f r j J : is , . vba F | Laie Py an a ly nis 4 bate iy nak Oe Loy) ae Be a Ma ay “ ay Wu) y t Pitny” u ‘ 7 Pixs j r \) A ‘ ‘ | } 4 ( j \4 ( y ‘ | ‘ ew ; j { j ; i | } ‘ uf we i ' ; { i ' it {o/h} i F Petites py elty : s } ' ; BPs VLAN Y ii a ae WJ f n ' LW L Al bi : ) 1 f } ' iy yey 4 ett et i NWSE I Wy Fy Seat in ‘i int Y ny Ha We tw 4 ) y uy \\ w ot ' ‘ rt Ny _ bth H x) t i ie rr Depo t i 4\4 4 \ é t , y bignlt oe yep a Aes) Hike Ree Yn rau pny A | mu Ry ions Wil. nd ’ ‘ ‘ 1 \ LIANE Lots ” ‘ ' "\ f i { \ j i ea 1 ay 4 Ti } \ { h i ‘ j Uy ie 4 4 \ \ i uh i ; Wha 1 ; Mod | ek | f ps6 5 Ht Waid i, ’ 6 py ; va { i ‘ Thy, ’ ‘ ») t vy ih 4 ' , : ' i beiict iy p EN ‘ . : (ep nV A Noni it iy i MA Re i 7 p ‘ ; Ria YY { " "wy *) 4 ( y} } WW 4 ) tO ee My ' vn ; | n bi } 7 \ f ) MINOW } it i Bude! iy Aa wie i Ai 4 ra re ey i " ' 4 ? f ‘ Ahad ite i] 4 / { ] wee \ { / y ay i Mo Waa ee ty i) . { i iil ‘ e/ A eo Ny t ai (ot 4) "Uh aval Ae } yi hae | ; aches } ‘ rena a ii by NT eae a Mii [ “ A A) t PA Meet j rh \We ey List pt bab ye DW aes ye An hah bi AeA a / Po sa WAC ile oh ‘ y 1 : | f ; j ti pg i { Ligy iv Wh) va } 4 Ei mien, Oe wef , yt " } AVE AV Ae sh ins v wid ay I Or, aN te es ay RA } Iron. ~ There is considerable magnetite in the Cambrian schists west of Burnt Mills. In 1903 an unsuccessful attempt was made to mine this magnetite, Limonite occurring in limestone has been mined at several places, The largest mines were the Grubb ore banks east of Shenks Ferry. They were operated from 1840 to 1885. ‘The best ore was removed, and the remaining deposits are believed to be small. At least, present conditions ado not warrant mining of the known Geposits. i, he 4 ’ ; : * 4 i) ye ( cer be ak) et y . Mu \ § ey Oi, y pv! oa) j - Ae Sy tex a Yt tue et? } "© an YY ¥ i if oP sae oh ore ; uM : V A ‘ Me a . eet wwe 0 pure iO RN DONO gett 2 ait gn Se ve 4 wm tae oh ad eT wa WE PO RP ¥ : Pear SE t TR Cae ae pee ‘he: my ’ ‘ ‘ ‘ « : 5 z ee ae) : P 4 . P \e - Lig K: : 4 ‘ nae Ph be ee 8 d > i i P } ts pe ae * : , " Ne Py ie si 4 ; a Ath OM, U ' a Tithe ai @ Aa aie Ae L ae 4 : f ' ni { te J ‘ \ ’ H i rH ‘ j 1 i) A y i ‘ ; 7 ry a ’ i j i i . ‘1 ‘ ' j ‘ } ’ : r \ AL af ‘ i i ' ‘ere ‘ i ; i f Ea a wl , ‘i Pe SPY ote alah gk r } 4 ; j ' Ae Peake ) 4 V7 A . f ‘ F 4s i{ i} i y \ rie Wy f j y ANN the ; | as hi - av & : | r ‘vi hat ACAPTRUA tt ee y uh eit ‘ i fa; ASAE hg ; 1 » { } iv) Vee OV) MP te) unity Hf tay a gary eat AT ek! "t tt i VANS bey ' ii } 2 Pri * aya : F oda if an we tae) U yY bs ‘ Dog ep re he cop igs ma) 4 es ae m te qed 4) Bids pda ; ’ 5 bas 4 he Zs ( oy od { 7 a : iy) fea Pe as Tala PAG AEE ae Abbie f ‘ "4 eA MR a ern | BE LA RNIN EHTS MRE Att fi i : a! : a, (P » tay Ty) et Y i TRAC RAO eS alt rtd ; Amin ¢ ny ny 4 | i 1 AS F ‘Oats \ i ? Me ws ama 4 aia i ono ee 2 Pet Ali v Payee ae GEOLOGY OF THE eee esee BERRY QUADRANGLE \ MA Washingionbore ‘ pare Diana On a (ie ey A IT eee x Mitt terswi i¢ n 43 oe (rd nel ha Me he i veel - — : ——— wl geey ete orb! ty e ae rH wh, ca ie Seals pe oe A PANO OL \ + st "ak L ye id ‘ % ln domewlior- a oad meee ene state a A j ' Leal Soe We 9 fap ete Ae ee ENE 1 * 3 a! se ra ee es Ret ys a ~ad West Wille a i] resswell Stra‘ Go ree 2s se > A / ae i PR Brie wii 2 4, Sah. Bh ntal tam hl ote, | TLS Mt ot Nas oo tia ith a “ae Rp Sole arto sh YL LORIN Bn NEO Se Re ‘>, fa mie Pt th LE LY Fis aie Py ead t tee ~ SSL. wat a pd ee ey ! 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Al SEOMENTAGY Re ROCKS aCe Perens omy eee a wwe [oe] | (LZ So} ese gh 5 esa = Sete Poe t Be acs Primate: SS ee Poe a aaadnny hl — krenesiong Aniiitam a perce Guarizge & Altvte Rov Serpentine & (net doskanwihea ) Chlikite Setlst Wadehizken Schi 4) Maryarle Dy nba Soa sto 2 " Baty, s $ > 0 a hin part Grdovician ‘ ih Aertel SCALE 3 ( re 2 GMICES BUSY 7 20s “eEar gp ae Ne ar 3 a i. Sears er TSN ad RAMA he to AF 7 | iim * i ; \ : : ; Sat eric Tae 1 ra y f q AY 4 ‘ ; 2 Vee ee aa 8 ; TOTO ELIT { ‘ Riv Tid ‘ a , ; td » r : ' AY ¢ f : { | y § i a : ' " ‘ ' ‘ . ‘’ ray | : 89 , Si wy j ter ; ‘ wy 4 A SiN, } - : Ae,» ere i As! - ition ah Tee i f \ , ; ? ‘ ! f ity be 4 / iy ’ , } \ \ } Ay | NEE } ae y * ™ ‘ +e" “ iwaned ; vi ‘J d 4 : ; \ ih t i - J 1 ve 4 \ ‘ v, ae } Lal Fy ah 2 ’ ‘ A vi mt DE a ; Pry, 43 ' “4 is ~ wy ‘ Wes : ; ng \ ' , i fy ik N tty ’ t hae ‘ ; ‘ 4 e ‘ : i R ; \ : 4 t ND the \w N b 1 alla ! 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