EAS 423: Sedimentology and Stratigraphy Measuring Sedimentary Structures for Paleocurrent Reconstruction

Objectives: Today’s exercise will incorporate several field data collection skills with some common analytical tools to help us develop our abilities to gain valuable information from sediment structures commonly found in our region. During this exercise, which will admittedly take more than just today, we will complete the following tasks:

1. Use compasses in the field to measure sedimentary bedding and structures; 2. Practice observing and sketching features at various scales; 3. Take detailed, accurate field notes to document our data and experiences, including grain size and rock descriptions, stratigraphic relationships, and sedimentary structures; 4. Compile directional (orientation) data using a Rose diagram; 5. Use field measurements and rose diagram results for paleocurrent reconstruction.

Background: As most of you know, the Allegheny Plateau and the Appalachian Basin are underlain by the Catskill Delta, which contains a diverse suite of sedimentary rocks, indicative of their depositional environment (Figure 1). During the late Silurian through the Devonian, the Acadian Orogeny built up an early stage of the Appalachian Mountains. Sediments were shed off the western slopes of this mountain belt into an inland sea, creating thick sequences of shales, limestones, and sandstones. Later, during the Pennsylvanian Period, these sediments were buried even deeper as Pangea was uplifting what we recognize as the modern Appalachian Mts. during the Alleghenian Orogeny. That is a lot of exciting geology! But how do we know all this?

We’ve discussed basic sedimentology and stratigraphy at length, and the role that transgressions and regressions play in sedimentary environments. But there is more to the story which allows us to develop more detailed pictures of these past settings. Several of Figure 1: Catskill Delta formation during Devonian Period. the rock units in our region preserve From SEPM STRATA, Society for Sedimentary Geology; Illustration by Lynn S. Fichter of the Department of Geology “paleocurrent” indicators. These are structures James Madison University, Harrisonburg, Virginia. within the bedding of larger sedimentary packages that give clues to the energy and direction of depositional mechanisms (wind, water, ice, and mass movements). One such unit is the Pottsville Sandstone (Pennsylvanian) which, fortunately for us, outcrops in several convenient locations in Ohiopyle State Park!

Because the Pottsville Sandstone represents a changing near-shore environment, we must first identify the sedimentary structures and what they imply. You should look for (and be able to define) the following:

 Laminar bedding  Graded bedding  Ripple marks (various types)  Cross-bedding In the Field: Previously, we’ve worked with Brunton and Silva compasses to measure strike and dip of units. We will be using these functions for this exercise to measure the general orientation of the Pottsville Formation within Ohiopyle State Park. However, we will also use our compasses to measure the orientation of the aforementioned structural features in the field.

We will begin our day at Cucumber Falls in Ohiopyle State Park. Review the map of the park, provided as Figure 2 at the end of this packet. Our goal is to make 3-4 stops, of at least 1-2 hours. At each stop, you are to complete the following in your field notebook:

1. Note and describe your map location; 2. Measure and describe the rock units in general; 3. Sketch the outcrop, paying particular attention to those units that have evident sedimentary structures; 4. Measure and describe present sedimentary structures, keying them to your sketches;

Work in groups of 2-3 in completing this exercise. Each student should be completing steps 1-3 on their own. However the measurements should be done as a group with one or two people alternating the measurement and the other student writing down the results.

In the Lab: Now that you’ve got your measurements, we’ll compile them into a Rose diagram (Figure 3). This is simply a circular bar graph (histogram) that allows us to display orientation data in a way that matches that data with its compass direction. Rose diagrams offer a quick, clear visual aid to draw conclusions about trends in our data.

Ask your instructor for as many Rose diagram blank sheets as you’ll need, based on the number of rock units you’ll be analyzing. We’ll go through this simple procedure as a group. Once you’ve completed the diagrams, choose the three which give the clearest indication of trends. Using these three “best” examples, complete the following tasks and write up your results as a historical reconstruction of the time/space of the Pottsville Sandstone on which we focused. Your write-up should be 2-3 pages, and should be heavy on connections between your field observations and your paleocurrent and paleogeographic interpretations.

Your write-up should include:

1. A BRIEF introduction explaining the project and general geology of our site(s); 2. Explanation of your site selection and Justification for these diagrams as the “best;” 3. Results – an explanation of the data including (not in the page count) any tabular data as well as the rose diagrams themselves; 4. Analysis of results, including the interpretation and significance of the findings; 5. Conclusion that includes the implications of this site evaluation in the historical context of the region.

Write-ups will be graded on a 25-point scale, using the following criteria:

1. Neatness and Clarity: 5 points 2. Completeness: 5 points 3. Geological Reasoning/Accuracy: 15 points

River El. 980' 1500 To Normalville 2000 To PA 653 &

1400 & PA 711, 8 Mi. 1900 Laurel Highlands 2400 Hike/Bike Trail Continues Youghiogheny 1300 2500 1200 2000 Hiking Trail 55 Miles to McKeesport SOMERSET Laurel 2300 2200 1100 2300 Run 2200 2600 Bidwell 1100 FAYETT Run 1200 River 1100 1800 Dra 2100

1500 1400 1200 Bear Run Run Road 1600 1300 1700 ke Bruner Run, 2100 1400 1600 Center 2000 1300 Boater Take-out r E

No Bicycles Allowed 1900 Bea BEAR RUN SR 2017 1800 STATE GAME LAND 111 2500 Run (Road Very Steep & Narrow) Road 1700 Bear 1800 NATURE 2300 Run th 1500 1700 . 1600 1600 T-527 RESERVE N (High Clearance

Johnson Road Lick 1600 1300 Vehicles Only) 2400 1600 1400 1600 1600 1500 Burnswor ner Rd 2300 Entrance to COU 2200 1200 T-896 Bru 2500 COU 2100 Fallingwater 2000 1700 1500 Run 2300 NTY 1900

NTY River El. Trail Cam 1800 1700 1280' 1600 2400 p Bike/Hike Trail Continues Bruner 1700 1500 Summit Run 1400 Trail Approx. 2 Miles to Confluence 1400 Run Old Mitchell River 381 Place er Ramcat 2200 Riv 1200 CAVE Launch Area STATE GAME 2400 1400 & Trailhead Mitchell Youghiogheny HOLLOW Waterfall 2000 1500 Run 2300 You ghiogheny 1600 Cross-country 1700 LAND 51 Gate 2100 1800 1900 Run Ski Area & Maple 2000 1900 1900 1900 1800 1500 2100 Trail Waterfall Sproul Trail 1800 Trail Hall 2200 2000 Stulls 2200 er 2300 Sugar Sproul Rd. Sugar Run 1600 Riv 2400 0 Rock 200

1600 2100 Run 1700 1700 T-523 1400 1600 S 2000 2500 1800 u 1500 g Kentuck 1300 a Fechter Trail T-844 Spring 2600 1900 r 1500 T-868 Run 2700

Trail Trail TRAIL INFORMATION Road Run 1900 Rock 2800 Road Beech Trail Jim Hiking Trail Contact Loop Station Run Spring 1300 Road (High Clearance Mountain Bike Trail 2000 Group Tent Vehicles Only) 1800 2100 Road ghiogheny Cross-country Skiing Road Run Camping Run

2000 1700 an King 1800 You h Beech Snowmobile Trail at Run n Tower r Run Jo a 1700 1700 2900 i 1700 1900 r 1500 1800 Backpacking Equestrian Trail b 1600 Trail n 1600 1600 Great 1600 e Trailhead 1500 e Blackberry T-523 r il Trail Shelter G 1900 1800 Gorge Highlands 1500

Sheepskin

1600 Tra Youghiogheny 1400 e Fire Tower 2900 Tr. 1400 1400 Ohiopyle Laurel Fir River Trail Holland Heliport Jonathan Loop, Take-out Hostel 1300 (Great Allegheny Passage)

Active RR il

KENTUCK Great 1300 Youghioghen 1600 1300 Tra 1700 1900 Other Trail 1900 1800 1500 1400 1800 El. 2920' Middle Yough, Boater Take-out & Trailhead 1600 2100 2500 Kentuck 1500 1500 2000 2200 2300 1300 To Confluence & C 1400 2400 a Baughman PA 281, 3 Mi. m OHIOPYLE To THARP McCune Hill p Trail Trail Waterfall y g KNOB NATURAL AREA 1800 THE FLATS Dunbar Gorge FERNCLIFF r 2800 o T-796 u Sugarloaf n 2000 Sugarloaf 1600 Road d Whitewater Craft River Gate SR 2012 1700 1800 R Road o Playground Launch1500 Area & SR 2012 2700 a Long Road 1700 d Softball Park Office Trail 1700 Field Slides 1800 Train Station & 1900 1600 Sugarloaf Baughman Snowmobile & 2800 Visitor Center Cascades Rock SR 2019 1900 Well Mountain Bike Area 2600 Blue Symbols Mean Accessible 1800 Waterfall 2500 1900 Kentuck Run Cucumber Meadow 1400 Sledding 2700 Public Phone 2000 Road 2000 Falls Meadow Run Area SR 1055 l i Run Trail Gas First Aid Station a 1600 r Trails 1900

2100 2400 T Sugarloaf SR 2010 2300 2200 Sugarloaf d X Amphitheater 2500 e Knob Roa rg 1600 Gate 1700 o 1500 El. 2640' Restrooms G le

2200 Road Lyt 2000 t Wetland Dunbar Water 2100 a Guided Raft Tour 2200 Food Concession

e Treatment r Check-in & Parking Private Boaters Changehouse G Park Office System Run 1800 Grover Equestrian & Showerhouse/Restrooms Parking il STATE GAME 1500 T-463 Tra

2300 Run Road Picnic Area Branch Silbaugh LAND 51 2100 Road ge 2700 1700 1600 Picnic Pavilion 1900 1500 Rid 1800 North Cucumber Run 2000 2700 Camping 1700 1600 1800 Pressley 2800 1900 Road Sanitary Dump Station 1500 Linn Run D Mount Pleasant 2000 inn Overlook 1600 e 70 rb 2600 Yo Scottdale Laurel e 2400 ug 76 SR 2011ll 2300 h Summit R Laurel io d 2500 Rapids gh en 119 2200 y R Road 1500 iver 2100 Kooser 2600 201 1700 Parking Connellsville 31 2100

Laurel Hill Cucumber 1800 1700 2500 51 Dunbar Normalville 1800 State Highway Laurel Ridge 2400 381 653 e Ridge 1900 2300 FAYETTE l Hard Surface Road y 381 p 2200 Uniontown 2000 OHIOPYLE STATE PARK 2300 o Ohiopyle i 1700 Unpaved Road OHIOPYLE 281 h 1800 1600 O Middle 1/2 0 1/2 1 KILOMETER

N - 1900 State Park No Hunting

Farmington Confluence 2200 l

40 l SOMERSET i 2100

h State Park Hunting

k 1/2 1/4 0 1/2 MILE

l 1900

a Ferncliff Natural Area h MD. 1900 WEST VIRGINIA 68 C 1600 1700 1800 Archery Hunting Only To Chalk Hill & To Farmington SCALE: 1" = APPROX. 0.47 MILE 1800 US 40, 5 Mi. & US 40, 4 Mi. 1900 CONTOURS ARE ON 100 FT. INTERVALS 0

Figure 3: Rose Diagram