Geology Raven Run Nature Sanctuary

GEOLOGY OF THE RAVEN RUN NATURE SANCTUARY completed March, 1985 @over Picture; The stone foundation of Evans' mi11. GEOLOGY OF RAVEN RUN NATURE SANCTUARY Introduction to the trail quide Geology is the science of Lhe earth and L11o~:owho study geology are called geologists. Part of a geologist's job is to determine how the rocks we see today in quarrys, r-oadcuts, parks, and other areas, were ori y inall y formed. Haven Run Nature Sanctuary is located on Lhe eastern edge of the Bluegrass region in cent;ral Kentucky. This region is a broad, oval platform that geologists call the Jessamine Dome. The Jessamine Ilorne is part of an even larger feature called the CincinnaLi Arch. Figure 1 shows how millions of years ago the sediments in central Kentucky were raised relative Lo I eastern and western Kentucky. The area that was relative1 y uplifted is called an arch. The areas ttml; PENN. 1. plan. ORD. LATE PALEOZOIC 220 nllllon vm.18 ago 4 ARCH END OF PALEOZOIC 100 mllllon v.818 ago REGIONAL EVOLUTION of the CINCINNATI ARCH CENTlAL IlNTUCIY were relativc?ly downdropped on either side of the arcti are called basins. After the arch was formed erosion re- moved great quantities of rocks and sediments form the arch. This left older rocks exposed on top the arch and younger rocks exposed in the basins. Since Raven Run is located near the top of the arch, some of the oldest exposed r-ocks i ri the state are found here. Most of !;he rocks you can see in the park are called carbonabes. 'rhese types of lacks are predominantly rnatle-up of the mineral calcite. Carbonates are formed irl warm, shallow seas,often or in part from the remains of small sea creatures. When these remains are preserved Lhey are called fossils. Figure 2 shows how geologists subdivide the carbo- nat,e rocks in the park. The lower and therefore older carbonates are called the High Bridge Group. The group is divided into three formations. Formations are used to classify rocks that are similar and can be mapped over large areas. At Raven Run, the High Bridge Group consists of Ltie Carnp Nelsorl Limeston Format ion, the Oregon Forma- tion and the Tyrone Limestone Formation. The upper and therefore younger carbonates are part of the Lexington 1,imest;one Format ion. The L,exington Limestone Formation can he further subdivided into specific members. Members are sin~plya more detailed c1assifical;ion. Three of the lower members of the Lexington 1,imestone are present in Ltlc park. 'T'hese are Ltie Curdsville Member, the Grier Mem- ber and the Tanglewood Member. The members of the Lex- irlg tori I,in~estone Formati on are general 1y buried beneath the soil on the upper. slopes and'ridgetops of the park. liowevor., the format,ions of the High Bridge Group are s~)ect,acularlyexposed in the gorges and along the trails of Raven Run.. 'I'he carbonate rocks that make up these formations were fornted in a shallow sea that covered much of the c?asLerri [Jriited States over 460 million years ago. This Lime was part of what geologisLs call the Ordovician period. Iluri ng the Ordovician period the Raven .Run area probably looked 1 ike the tidal flats and shallow seas of the Bahama Tsl ands today. However, many of the creatures that, lived in this Ordovician sea were very different I HIQH BRlOQE QROUP LEXINQTON LS. 1 rora \,he creatures we see today. Figure 3 is a i llustra- Lion of what the Ordovician seas of the Raven Run area might have looked like 460 million years ago. In those seas were squid-like creatures with shells called ceph- alopods, strange cousins of the horseshoe crab called t,ri lobi tes, creatures that resembled underwater flowers called crinoids, prin~itive snai ls called gastropods, prim- itive clam-like organisms called brachiopods, small coral- 1 i ke creat:t~rescalled bryozoans, as well as many rela- Lives of the modern corals and marine worms. F'icjure 4 is a geological map of the park. It js on pnye 6 of' I,his pampl~let. Geological maps are used to show the: rock formations occuring at the earth's surface. When you start out at the barn, the map indicates that I.l~erocks right below your feet are part of the Lexing- Lon Limestone Formation. When you get down to the water- falls at stop 4 the map indicates that you are standing or1 rocks which are part of the Camp Nelson Formation. - 'I'hjs pamphlet is a trail guide to the Raven Run Not,ur.e Sanctuary. Points ol- geological interest along Lhe Red Trail are marked on the map (page 6). Brief des- criptions of the points are listed in the following pages 61s geological stops. 'These stops can be seen from the desiynated trai 1s as shown on the map. Walking off the Lrail can be very dangerous and is discouraged. Please do not remove or vandalize the rocks or fossils in the park. 'This park is meant to be enjoyed by everyone. Leave on1 y footprints, take only memories. LIFE IN THE ORDOVICIAN SEAS 4 60,000,000 years ago fig.3 1 1) horn corm1 3) brachlo~ods 5)aloe. 7)marlne worm 8) lrlloblta 2) colonlal coral 4) crlnolds 6) ca~halo~od 8) 0a~lro~od 10) bryoroan GEOLOGIC MAP of the RAVEN RUN NATURE SANCTUARY CncLTinuM TO?^ flg.4 after Black (1967) STOP 1 As you came down the hillside on the ~edTrail you were walking over the Lexington Limestone Formation. These rocks are called limestones, because they.are pr-e-- dominantly made up of calcium carbonate or "lime". Figure 5 is a sketch of the creek at skop I.;.When you look into Lhe creek bed. you can seef'tkat. there are many parallel cracks in the limestone..Geo~ogistscall these straight cracks in the roc~~;,~:jo.i.rits~Atthis SLOP the joi.nts are all alligned. in.the. .. sarne direction. At other. points along the t,F+"iii..yow'may see an additional set of joints alligned:.approx-iinately 80" from this set. Joir~ts can make the rockvery weak, so that it is easily broken apart. As yoi1.walk along the creek you can see how water falls have formed where rocks have broken a.Long the :joir~l:s: JOINTS BLOCK DIAGRAM of the RAVEN RUN AREA -- -- - - - A). Park entrance 8). Barn and parklno C). South Fork Raven Run Ck. 0). Mlddle Fork Raven Run Ck. El. North Fork Raven Run Ck. F). Rlver overlook VIEW (3). Chandler Ck. FROM ACROSS THE RIVER (ehrt) 'The secontl stop is located 200 feet past the trai 1 jurlction. If you look to your right about 20 feet up from Lhe trail you can see a protuding ledge of rock. The ledge is made up of limestone from the Curdsville Member of the Lexing Lor) Leimestone Formation. The 1imestone beneath the ledge is from the Tyrone 1,imestone Formation. When two formations meet like this, it is called a stra- tigraphic contact. Note the differences between the two types of limestone. 'I'he Cur-dsville Limestone is very rough to the touch ;iri$ contains many fossils. The fossils are more easily seen onzthe underside of the ledge. On the other hand, the TyronehLimestone is much snroother to the touch, and (:on tsiris much fefnler fossi1 s. * '- COMMON FOSSILS horn corals crinoids bryo roans burrows Figure 6 shows sonre of the fossils you can see in the ledge rock. These fossils are the remains of creatures that lived here over 460 million years ago. Figure 6 also shows the curious straight lines that you can see in the Tyrone Limestone, beneath the ledge. They represent a different kind of fossil. While the fossils in the ledge represent the actual remains of an organism, these 1 ines l.epr.esen t the tracks or-ganisms leave behind. They were orlc:e the burrows cjf small worms and clams. When burrows are straight-up 1 ike these, geologists call them 'verti- cal bur~.ows'. They are evidence that creatures were living in the mud on the ancient tidal flats. Apparently when the tides came iri, the creatures came out of their t)urrows to feed. Then when the tides withdrew, Lhey re- t,r-eated back into their moisL burrows so that they would not dry-01~1, in the hot; sun. STOP 3 Water seeps out of the limestone rocks at sevr-a1 places throughout the park. When these seeps are large enough they are called natural springs. Figure 7 stlows how a spring may form. Rain falling on the earth's surface seeps into the ground. As the 'groundwater' travcls through the soil it becomes mildly acidic. CarbonaLe rocks, such as limestone can be dissolved underground by these acidic waters. Often the groundwater works i t's way down joints like you saw at stop 1. As the acidic water moves underground it en1 arges the joints, for-ming solutional cavities. Over a long period of time, largc amounts of the limestone may be dissolved away, f'orminy a cave. Another feature that may form in this situation are bowl-shaped depressions called sinkholes. All of these features; the seeps, springs, sinkholes, solution cavities, and caves are called 'karst' by geologists. They are common throughout Ken Lucky. In fact, Kentucky is one of the most famous karst areas in the world. rock debrla SEEP NATURAL uCREEK KARST FEATURES There are many things to see in this area.

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