Cacapon Institute

• vol. 4, no. 3 Summer 1992 Cacapon PUBLISHED BY PINE CABIN RUN ECOLOGICAL LABORATORY Geology of the INSIDE Cacapon River Basin 6 Letters to the by Eberhard Werner,Morgantown, WV Editor Let's begin by looking at a map. Any plied slowly the rock layers will bend map will do as long as it shows the streams. (up to a point). 7 A drainage map of West Virginia, for ex As you can see in cross-section (figure Cacapon ample, reveals regional differences. In the 2), the surface of the earth may not mirror T-Shirts center of the state, streams do not form any the folding of the rocks. There are instances for sale! particular pattern - they simply wander where a ridge coincides with an anticline about in the general direction of the nearest and a valley with a syncline, but the reverse larger stream. In our part of eastern West also occurs. It all depends on the resistance Virginia, though, the larger streams run of the various layers to erosion, and how ac parallel. Only a few short segments of the tive the erosional process has been. We will mainstems flow in a direction other than discuss this further in a bit. northeast-southwest. If you follow the Fractures - Sometimes forces in the Cacapon (figure 1), you will see that it earth are applied fast enough or the bend proceeds for long distances in a north ing is so extensive that the rocks break. easterly direction, occasionally jogging Look carefully at an outcrop and you will sharply right or left. see some breaks. Most of these are simple To understand what has caused this fractures with no significant movement of curious drainage pattern we need to ex one piece with respect to theother; these plore the rocks underlying the surface. are called fractures or joints. Where there has been significant mQve Structure ment along the break, it is called a faull. The field of geology concerned with the What movement is deemed significant arrangement of rocks is known as struc depends on many factors. Sometimes it tural geology. The geological structures must be far enough to show up on a map, relevant here are folds and fractures. sometimes just being able to see that the Folds - You may have noticed that layers no longer line up is enough. Basically rock layers in the basin are either flat or it depends on who is looking and why. bent. Keep in mind that most folds are too The major structures of the Cacapon 8 large to be seen in their entirety; you only River basin are shown in figure 3. At this scale only the largest folds show up. Lab see a small part. Folds come in two basic News types: anticlines, where rock layers are Smaller folds and faults can be seen on folded upward at the center and slope more detailed maps (e.g., Tilton and others down away from the center; and synclines, 1927, Dean and others 1985). 9 which are like anticlines turned upside Cacapon down (figure 2). Kinds ofRocks Natural Folding comes about when forces Geologists divide rocks into three basic History within the earth compress a piece of the types: igneous - those formed from mol earth's crust (See "Cacapon Natural His ten ma terial either on the surface or within tory", p. 9 this issue.). If the forces are ap the earth, metamorphic those altered I r lab from previously existing rocks by heat of these and quartz, the normal name is needs: and/or pressure but without actually melt sandstone. Sandstone is mostly quartz, but ing them, and sedimentary - those formed it contains other minerals as well. For ex from tiney pieces of various kinks of ample, calcite ("lime") and hematite ("iron") canoe trailer materials laid down in water. commonly cement the grains together. The With minor exceptions, the only type of same idea applies to shale and siltstone. photocopy rock that occurs in the Cacapon River basin Limestone is different from other machine is sedimentary. Sedimentary rock usually sedimentary rocks in that it is built of foTITIS in the ocean near shore, or where material taken out of oceanic water by rivers slow down so they no longer carry plants and animals that build their shells or the load. As materials pile up on the bottom skeletons out of calcite ( and other related of the water body, their own weight com minerals). These skeletal remains are the presses the bottom layers. Minerals from grains which form limestone. Most caldte water in the pores come out of solution and grains are deposited near where they were ~S-:acapon £~ cement the grains together, and the result is created by organisms, unlike sandstones is published quarterly, rock. whose grains have been carried long distan with the arrival of each ces by rivers and ocean currents. equinox and solstice, by Pine Cabin Run Ecological Laboratory, Rock Layers Route 1, Box 469, Cacapon River Basin In the Cacapon River basin, different High View, WV 26808; o IOm!l!!!> FAX & phone kinds of rocks are found at various depths. (304) 856-3911. Rocks of the vertical column can be as signed to different formations. The name ap BOARD OF plied to a formation is the place where it DIRECTORS Nancy Ailes was first described. For example, the George Constantz Helderberg Group is named for the Helder Michael Dixon berg escarpment of east-central West Vir Ronald Knipling ginia. Identification of layers is based on Jane Licata James Matheson characteristics of the rocks themselves and fossils within, or more recently on ages STAFF determined by the rock's level of radioac Dr. George Constantz tivity. Most of the Cacapon River basin's Director rocks, listed below by increasing age, are Nancy Ailes Cacapon Editor ,.. detailed by Cardwell and Erwin (1968) and David Malakoff by Hobba (1985): Senior Associate I. Mississippian Rocks (formed 360 - 320 million years ago) SCIENTIFIC ADVISORY B.JARD - Pocono Group (570 feet thick) - gray or Dr. Joe Calabrese tan, massive, fairly hard sandstones Dr. Stephen Fretwell topping ridges in the western part of Dr. Robert Kahn Dr. Michael Masnik Figure 1. Stream network of the Cacapon .RIver basin the Cacapon River basin. Dr. Chris Sacchi as shown on the U.S. Geol. Surv. 1:250,000 scale maps. II. Devonian Rocks (formed 408 - 360 mil The two small arrows show the location of the cross lion years ago) COUNSEL section in figure 2. Charles Licata, JD - Hampshire Formation (2000' thick) mostly shales and fine-grained Sedimentary rocks can be classified by PHOTOGRAPHER sandstones, with some coarser grained, James Holmes the materials making them up; and most people recognize their names: shale, massive sandstone beds; mostly red or brown; generally on hillsides in the Pine Cabin Run siltstone, sandstone, and limestone. Al Ecological Labortory though that classification looks simple, western half of the basin. is a non-profit, tax there are complications. Shale, siltstone, -Chemung Group (2500 - 3000' thick) exempt grassroots alternating sandstone and shale beds, organizaHon and sandstone are named for the size, not dedicated to the composition, of the particles making them with each bed only a few inches thick; ecological preservation up. One can find sandstone made of calcite, mostly yellowish brown in color; very of the Lost, North, and fossiliferous in some places; mostly on Cacapon rivers. quartz, or hematite. Although no one would normally call a rock made entirely of hillsides in the basin. Printed on recycled sand-sized grains of calcite or hema tite a - Brallier Formation (1300-2170' thick) @paper. sandstone, most geologists would call them mostly greenish-gray, very thin limestone or rock hematite. If it is a mixture bedded shales and siltstones, other- 2 • Cacapon vol. 4 no. 3, summer 1992 Published by Pine Cabin Run Ecological Laborato?1j wise fairly nondescript; weathers III. Silurian Rocks (formed 438-408 mil readily and tends to slump into masses lion years ago) of shale chips. • Tonoloway formation (200-400' thick) -Harrell Shale 025-300' thick) dark gray, sometimes very dark, thin brown or gray to black, thinly bedded limestones or dolomites; often laminated shale; with a few fossils. containing appreciable amounts of -Mahantango Formation (300-1000' silica. thick)-mostlybrown sanay shales with -Wills Creek and McKenzie formations a few thin beds of sandstones and limy (400-800' thick)-limy shales qr shaly sandstones; may be very fossiliferous. limestones for the most part; most of - Marcellus and Needmore shales (500 the rock is actually gray but is almost 900'.thick)-dark brown or black shales always stained red from weathered with little variety, splitting easily into material washing onto it; the two for thin flakes; one or two limestone beds mations are sometimes separated by about 20 feet thick toward the base of the Williamsport sandstone which the formation. may be up to 100 feet thick. -Oriskany sandstone 000-500' thick) -Tuscarora Sandstone (50-300' thick) white to brown sandstone, locally mostly thick-bedded light gray limestone or sandy limestone; cemen sandstone, very resistant to weather tation varies from very strong to almost ing; tops the highest ridges in the east "With none; silica or calcite; chert layers are ern portion of the basin. mmor sometimes found at the top and bottom IV. Ordovician Rocks (formed 505-438 mil of the formation, although either or lion years ago) exceptions, both may be absent. -Juniata and Oswego formations (600 the only -Helderberg Group (300-600' thick) 1200' thick)-mostly red or gray, thick light colored, usually gray limestone; bedded sandstones; not as resistant to type of rock upper portion is thin bedded, with weathering as the Tuscarora, but still that occurs cherty layers at the top and shaly layers quite resistant.

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