Exploration of Rock Creek Park-North Washington, D.C. July t 7, t 989 Field Trip Guidebook T209 Leader: James ~ O'Connor American Geophysical Union, Washington, D.C. Copyright 1989 American Geophysical Union 2000 Florida Avenue N.W., Washington, D.C. 20009 ISBN: 0-87590-698-2 Printed in the United States of America Rock Creek Park Rock Creek Park ... ~ ;- ;O:~TtR 4i REEtt • ". EDICALIE Iil r.Z.. I ~~ ... CENTER 'S -0~ Tennyson Street . -I'·'U~•.r,·' II OV ~ Aspen Street CJ Batlleground National Rlttenhou.. Street ~\ ! Cemetery j r PARK\ til .. il CD = Nature Center & Planetarium PUBLIC \,.; #' CGOOULRFSE. .it. ,Rll1enhouM St 6'qifj'"b ® =Stops _III"" FortSteven.;<;,t$.(--1~·I - r --.., .-.-\ tQ(, FORT '- _...-,STEVENS RK > 11)0 Sireet or •'" • Street r Brandywine lbennarte • . " ~l c .f • 'lIden II /~] ., . $- .. .", WOodley CNoDrth o 0.5Kilometer o ,0.5Mile IGC FIELD TRIP T-209: EXPLORATION OF ROCK CREEK PARK-NORTH James V. O'Connor University of District of Columbia, Wa~hington, DC Rock Creek Park is a special place STOP 1 for studying geology. Founded as the ROCK CREEK NATURE CENTER: city park in 1890, Rock Creek Park The building stone facing of serves as an oasis in the urban the Nature Center is made from the environment. Rock Creek Valley is a local bedrock. It was quarried steep craggy Piedmont eroded zone from Maryland's River Road district. where one can observe the bedrock, The dimension stone name is Potomac follow the evolution of the Fall Bluestone. Geologically the rock is Zone,and measure the topographically part of the Sykesville unit of the isolated Coastal Plain gravels. Wissahickon Group. This Piedmont Figure 1 is the map of the stops Plateau Province rock represents an to observe the general geology. early Paleozoic marine environment. It has been metamorphosed at least The Rock Creek Valley is a textbook twice with garnet grade observable. for research on the early Paleozoic Almandine garnets cause iron stains history. Metasedimentary and igneous in this building stone. Foliated rocks reveal the marine and tectonic blocks placed vertically or stories ofa proto-Atlantic Ocean. horizontally capture the eye. Metamorphic mineralalogy is set in Weathering of this rock fosters folds, faults, and fracture systems. a careful investigation of which Paleozoic tectonics is covered on way the rock layers are set and how the bluffs unconformable by gravels they respond to moisture attack on of the Mesozoic and Cenozoic. the foliation. The face of a layer The Cretaceous ancestral Potomac is used to highlight the mica sediments are also reworked into the laminae as opposed to the side lower elevation sediment deposits of view of layers. late Cenozoic age (Miocene ? Holocene). Figure 2 is a general The topography of the nature center geology map of the District. occupies a central high gravel cap Rock Creek served as a field site for that has been cut by Rock Creek. the 5th International Congress for Investigation of the gravels south Geologists in 1891. We will revisit west of the center gives clues to some of those same stops almost a the origin of the sediment. The century later and follow in the foot gravel is mainly cobbles that are steps of the early American pioneers: rourided and have the quartzite compo W. J. McGee, N. H. Darton, A. Keith, sition characteristic of the Blue G. Williams, and B. Willis. Ridge region (Weverton and Antietam Formations). This type of quartzite does not exist in the Rock Creek drainage basin. It also exists on the east side of the valley at the Carter Barron Amphitheater. Some of the gravel contains the fossils §skolithus linearis' which is inter preted as tidal flat vertical burrows from colonial worms. The gravels are Please NOTE: part of the ancestral Potomac gravel WATCH FOR poison ivy plants or roots deposits that make up the Atlantic BE CAREFUL of the auto traffic along Coastal Plain Province. Darton the roadside. labeled these gravels as Cretaceous Drivers will not expect you. and part of the Potomac Group (1947). SAMPLE COLLECTION is PROHIBITED These gravels also give a handle on in our National Parks. the age of Rock Creek,and the down- T209: 1 Figure 2: General Geology Map of District of Columbia Coastal Plain UnconsolidatedMaterials o 1 Artificialfill 2 Alluvium&sand o 3 Riverterracedeposits , c.: 4 Uplandgravel&sand 5 CalvertFormation " 6 AquiaFormation I - 7 MonmouthFormation ...... 8 PotomacGrp(clay&siltfacies) . 9 PotomacGrp(sand&gravelfcs.) \.,. Consolidated Rocks&Weathered Residuum PiedmontPlateau (, 10 Kensingtongneiss ~ ) 11 Georgetownmaficcomplex /. 12 Gmcomplex(ultramaficrocks) .. 13 Wissahickon Formation ~ J ., o (peliticschistfacies) • ' I '" miles 14 Wissahickon Formation (diamictitegneissfacies) STOP 2 CLASSIC PIEDMONT TOPOGRAPHY: The Piedmont is characterized by cutting of its valley. The gravel its rolling hills. The view from the boundary with the underlying bed woods across Glover Road (formerly rock exposed on the sides of the Ridge Road) shows the topographic hilly topography in the park leads changes. Drainage divides occur here to springs and stream headwaters. with Military Branch flowing east to Native Americans used these gravel Rock Creek and the southwesterly deposits behind the Nature Center ephemeral flows combining into Grant for tools such as tomahawks. Branch. Runoff from small parking Archeological surveys indicate the lots highlights the problems with Indians followed the ancient channel runoff volumes and point/non-point beds which make nice visible contour source pollution for stream and lines on the hillsides. groundwater quality. T209: 2 STOP 3 Washington (1921) of the nearby JOINT SYSTEMS in Carnegie Geophysical Labs and petro KENSINGTON GRANITE GNEISS logy fame (CIPW system). A.K. Sinha This roadside outcrop at the base and his students (1979) have most of Grant Road illustrates two major recently analyzed the rocks for the problems of the local bedrock. First geochemical fingerprinting of Mary is a joint system. Three major land plutons and age relations of fracture sets occur and form an Paleozoic tectonics. This abandoned intricate checker pattern that quarry is also the location for the allows tree roots and water to original radiometric studies by geo migtrate through and displace the chronologists from Carnegie Labs. rock blocks. Second is that moisture Using biotite and zircon minerals on the exposed rock surfaces as well from this quarry's rock, Davis as the joint plane fosters rapid (1958), Wetherill (1966) and others chemical weathering. Feldspars turn established the standards for com to clay very quickly and the biotite paring the dates from different mica leach their iron. Investigation atomic clocks to observe how the of the mineral percents in the out dates for each clock varied when crop demonstrate the mineralogy that taken from the same samples. will occur after breakdown. This This quarry was active during the stop shows the creation of saprolite preparation of the Geologic Atlas which is a clay-rich, soil-like of Washington area by the USGS in residuum that preserves the original 1901 (Keith). This stone has a structure and volume of the parent variety of names including Kensing rock but has few of the original ton granite gneiss; Rock Creek minerals and as little as half the granite;or metatonalite. The bridge original density. and the mill downstream document its use. Diaries and maps show the STOP 4 stream (Broad Branch) where the BROAD BRANCH or PIERCE QUARRY road is today while the quarry was The abandonned quarry was taken in operation. The fracture patterns by eminent domain from the Pierce observable in the quarry walls heirs in the creation of this park. indicate the ease of extracting Current environmental laws prohibit large blocks with smooth faces. resource extraction scars, but A detailed study of the joints in nature is slowly reclaiming this this quarry was part of a regional hole by biological succession. study conducted by R. Lopez (1982). The Kensington granite gneiss is He discovered a joint set particular a syntectonic pluton named for a to the Kensington itself. small Maryland town to the north. This bedrock was also a major This fold axis intrusion is a "salt building stone for northwest DC and pepper" rock with the biotite at the turn of this city. generally oriented as a foliated The Connecticut Avenue corridor layer. This rock was detailed by claimed as many as twenty-two Hopson (1964) as part of his re active quarries at one time. gional study. Carroll (1964) called this rock a metatonalite. It was first described by G. Merrill (1895) TABLE 1: Radiometric Ages of the Smithsonian,later by R.S. TABLE 2: Joint System TABLE 1: Pierce Quarry Radiometric Dating Results Mineral Sr/Rb87 Ar/K~O Pb/U Pb/U Pb/Pb Pb/Th 87/87 40/40 206/238 207/235 207/206 208/232 1. Biotit~ 305 380 1. Zircon 370 395 550 2. Biotite 350 2. Zircon 400 420 510 350 (FROM Davis) T209: 3 TABLE 2: ATTITUDE OF JOINT SETS IN ROCK CREEK PARK SET STRIKE DIP MAXIMA 1 N5- N22E 60-65W 8% 2 N12-N50E 20-40SE 5?t6 3 N58-65W 651'JE-8SSW 5% 4 N80-86W 75-85N 8% STOP 5 relate to the changes in trans MINI FALLS of BROAD BRANCH portation and the problems of The bed of Broad Branch changes fording a creek. Floods were also downstream near Brandywine St. involved with the downfall of The majority Piedmont bedrock the mill. The mill and spillway appears in the form of mica schists, (50 foot contour) were reconstructed metagreywacke and amphibolite layers during the WPA days of the 1930s. that are folded. The resistant Velocity of the river flow over the psammitic beds provided a stretch spillway created undercutting of of falls, pools, and mini potholes. the banks. Gabions on the east bank have lasted and provided strong bank stabilization here unlike the situa STOP 6 tion along other streambank zones. PIERCE MILL GROUNDS Inside the mill is the flood level Just after Soapstone Run marker for Hurricane Agnes in June, enters Broad Branch, we come 1972. This flood event is the high upon the confluence of Broad est recorded on the creek to date. Branch and Rock Creek. This region The local side street is named for is the upper limit of the mill the descendants of the Pierce complex owned by the Pierce family Family, the Shoemakers. in the last century. Typical of the mill era of the nineteeth century, the restored gristmill STOP 7 complex still has a false race, BLAGDEN'S MILLSITE & BOULDER BRIDGE overshot wheel for power, dam and Thomas Bladgen was a prominent mill pond plus some interesting landowner. He imported Irish hands building design. The national to work on stone and run his mill. park brochure for the mill shows His mill complex included a bone the orig-inal land tracts. A small mill to produce potash for fertili portion of the original Pierce zer as well as a grist mill. The Mill Road still exists on the promontory across from the mill was east side of the creek. The history known locally as "Pulpit Rock" be of the mill reflects the changes cause of the Sunday sermons given in D.C. from agriculture to the workers. The millrace is still urbanization, and from reliance visible but filled in. on natural resources to reliance Boulder bridge is a classic and geo on human controlled energy. The logic masterpiece built in 1902. Pierce springhouse lies in the Parallel pebble and cobble bridges median strip for Tilden St. but no longer exist except in photos. still has a cool flow most of the A topographic benchmark lies on the year. The Tilden St/Park Road bridge southwest end of the bridge and re over Rock Creek has its own cords 85 feet above sea level (Wash hundred year history. The different ington West Quad.). The boulders are stones on the abutments clearly local. The roadway called Beach T209: 4 Drive was built by a chain gang of strife in the United States from city prisoners and designed by Col. 1861-1865. A series of forts was Lansing Beach of the US Army Corps constructed around the nation's capi of Engineers. Intended as a scenic tal to protect it from attack by parkway, it is now a commuter high southern forces. Fort DeRussy and way until the weekend. Fort Stevens guarded the valley of Rock Creek. Fort DeRussy was built STOP 8 in 1861 by soldiers of the 4th New The FALL ZONE OF ROCK CREEK: York Heavy Artillery and was named The drop of Rock Creek in the short for their commander Col. Gustavus A. stretch from Military Road to Pierce De Russy. Fort Massachusetts was Mill is over 50 feet in a mile. Pot built on the top of the east valley holes, debris jams, and gravel point wall in 1861 but was lated renamed bars are quite evident along with after Brig. Gen. Issac Stevens killed the babbling stream. The Fall Zone in the Battle of Chantilly, Virginia. is a major geomorphic feature along in 1862. The only battle to occur in the east coast of the United States. DC was at Fort Stevens in July of This region is a zone of waterfalls 1864. The earthen mound for Fort at the transition between the Pied DeRussy still exists but the moat mont and Coastal Plain Provinces. is partially filled in and vegetation Besides waterfall evolution, knick is reclaiming the fort. Fort Stevens points and narrowness of valleys is a separate military historical document the zone on topographic park and is uniquely restored with maps. The Fall Line is the eastern stone logs. A military road connect end of the zone which extends from ed the fort system. The current New York City to Macon, Georgia. The Military Road is adjust~d for the Fall Line marks the end of tidewater oriented street plan for the city and the narrow valleys were heavily and no longer connects the circle used for water power or water supply of civil war forts. dams as on the Potomac or Susquehanna Rivers. STOP 9 FORT DeRUSSY: The defenses of Washington were Follow trail backto the Rock Creek very important during the civil Nature Center. T209: 5 SELECT REFERENCES: Clark, A.C., The Old Mills: Merrill, G.P., Disintegration of Rec. Col. Hist. Soc v.31-32, the Granitic Rocks of DC, GSA p.81-116, 1930. Bull.6, p.321-322, 1895. Coulter,H.W., and Carroll, G.V., Myer, D.B., Bridges and the City Selected geological localities of Washington, US Commission of in the Washington Area: Fine Arts, GPO, 96p., 1974. Jour. Wash Acad Sci. v.54,#5, National Park Service USDI, p. 153-159, 1964. Peirce Mill, brochure-GPO Darton, N.H., Sedimentary Forma 1975-585-439/86, 1975. tions for Washington, D.C. and National Park Service USDI, Rock vicinity: USGS Mineral Resource Creek Park Brochure, GPO, 1980. Map, Scale 1:31, 680, 1947. National Park Service USDI, NPS Davis, G.L., and others, Handbook 102: Washington, DC., The Ages of Rocks & Minerals: 1989. Carn. Inst. Wash. Yearbook 57, O'Connor, J.V., The City and Its p. 176-181, 1958. Creek: a Fluvial Case History, Fellows, R.E., Notes on the GSA Abstracts v.14,#1, p.68-69, Geology of Rock Creek Park, 1982. District of Columbia: Trans. O'Connor, J.V., The District of AGU vol. 31 #2, pp. 26 7- 277, 1950. Columbia, EARTH SCIENCE vol.38, Froelich, A.J., Prelim. Bedrock #3, p.11-15, 1985. Geology Map of D.C., USGS Open O'Connor, J.V., Urban Geology: File 75-537, 8p., Scale 1:24000. Satellite Parkland for the NPS 1975. Rock Creek Div.- UDC Geoscience Froelich, A.J., Thickness of Over Guidebook 12, UDC Press, 12p., 1986. burden Map, D.C., USGS Open File O'Connor, J.V., Landforms and Soil 75-538, 4p., Scale 1:24,000, 1975. Erosion in the Nation's Capital, Hopson, C., The crystalline rocks 5th Annual Erosion & Sed. Control of Howard and Montgomery Counties: Conf. Guidebook (UDC 13), 53p, 1986. in Geology of Howard and Mont. Cos., O'Connor, J.V. & Withington,C.F., MD., Md. Geol. Surv., p.27-215, 1964. Urban Geology of the Nation's Humphries, R.L., & Chambers, M.E., Capital in Ridky, R. (ed.) Guidebook Ancient Washington American Indian for Field Trips in Maryland & the Cultures of the Potomac Valley: GWU National Capital Area, NAGT/ES 26th Washington Studies f16, 36p., 1977. Annual Conf.(U of MD.), p.16-44, 1977. Keith, A. & Darton, N.H., USGS Geol Sinha, A.K. & others, Igneous Rocks ogical Atlas Folio 70 : Washington, of the Maryland Piedmont:lndicators D.C.and vicinity; Scale 1:62,500, 1901. of Crustal Evolution, Caledonides Lopez, R., (unpublished thesis), in the USA symposium, IGC Project, A Comparison and Analysis of the p.131-135, 1979. Joint Pattern of the Kensington Smith, H., Soil Survey of D.C., Gneiss and the Sykesville Formation USDA-SCS, GPO., 185p, 1976. in part of Rock Creek Park, Washington, H.S., Granites of D.C., Washington, D.C., Geology Dept. Jour. Wash. Acad. Sci. vol. 11, GWU, 48p., 1982 . #19, p.459-470, 1921. Inashima, P. Y., Archeological USGS, Washington West 7.5 Min. Quad Survey Report Erosion Control and Top0 graphic Map• Scale 1: 24000, 1965 . Bank Stabilization sites: Rock Wetherill, G.W. and others, Creek Park package 206-42, PS-NPS Age Measurements in the Maryland USDI-NPS Denver Service Center , Piedmont: Jour. Geop. Res. v.71, NPS Pub. 821-D30, 369p., 1985. #8, p.2139-2155, 1966. McClure, S.W., The Defenses of Wash O'Connor, J.V., Urban Geology of ington 1861-1865, USDI-NPS-NCP, the District of Columbia, in 49p., 1961. O'Connor,ed., Guidebook for McCormick, C.H., Milling in Rock the 39th NAGT/ES Annual Field Creek Park, USDI-NPS- Conf. Wash., D.C., UDC Geos. Div. of History, 1967. Guidebook 20, p.123-140, 1989. McGee, W.J., The Geology of Wash Owens, J. & Denny, C.S., Upper ington & Vicinity, Fieldguide Cenozoic Deposits of Central to 5th lUGS Congress, Washington, Delmarva Peninsula, MD & Del.: D.C., p. 39-63, 1891. USGS PP 1067-A, 28p, 1979. T209: 6