Today we are driving south to examine the sedimentary rocks which straddle the Mississippian-Pennsylvanian unconformity in southeastern Ohio. We will spend our field time describing and interpreting these rocks and completing a series of exercises designed for you to apply the various skills you have learned in this course. The completed exercises are due at 8:00 a.m. on Thursday, May 4. You may work in groups on these projects, but you are responsible in the end for your own observations and interpretations. I will also freely dispense little nuggets of wisdom which you may use in your answers, provided you understand them.

We will see a variety of marine and terrestrial, siliciclastic and carbonate rocks on this trip. You will need your handlens, grain-size card, and geologic hammer to perform the rock identifications, and your notebook, ruler and a pencil to record the stratigraphic information. I will supply Jacob's staffs, a Brunton compass, and plenty of encouragement. The exercises below are keyed to the stops in the accompanying road log.

At this outcrop on the side of the highway we see our first exposure of the Mississippian-Pennsylvanian unconformity. The rocks below the surface are the Middle Mississippian Logan Formation (familiar to us in northeastern Ohio), and the rocks above resemble the Lower Pennsylvanian Sharon Conglomerate. Because this Pennsylvanian conglomerate exposed here cannot be traced directly into the real Sharon Conglomerate of northeastern Ohio, we are forced to refer to it in quotation marks as the "Sharon Conglomerate". Awkward, but scientifically honest. Watch out for fast-moving traffic.

1. On the accompanying graph paper, draw a scale diagram of a portion of the outcrop, showing the geometry of the unconformity and the rock types above and below. choose an appropriate scale so that you can show as much as possible without losing essential details. The Jacob's staffs make excellent scale indicators. Reproduced below is the USGS guide for some appropriate lithologic symbols. (I will give you extra graph paper sheets on Tuesday in class so you can recopy your field illustrations.)

2. What is the rock type of the Logan Formation just below the unconformity?

3. What depositional environment can you postulate for the sediments of the Logan Formation here? Please describe the evidence you are using for this conclusion.

4. What is the rock type of the "Sharon Conglomerate" just above the unconformity?

5. What depositional environment can you postulate for the sediments of the "Sharon Conglomerate" here? Please describe the evidence you are using for this conclusion. The nature of the unconformity itself is part of the story.

6. What type of unconformity is this?

We will spend considerably more time at this extensive outcrop. The base of the exposure is the Logan Formation, followed upwards by the "Sharon Conglomerate", the "Sharon Coal Zone", and then a series of siliciclastic units which have not been named. This outcrop can be climbed easily at its margins. Avoid falling off any cliffs.

1. On the accompanying log sheet, draw a detailed stratigraphic column of the lowest 40 meters of the outcrop (or more if you can). (Extra paper will be available back at Wooster for recopying.) Your columns should have a horizontal axis indicating average grain size, in a manner I will have demonstrated to you in class. The lithologic symbols should again follow the USGS standard previously illustrated. Your lithologic descriptions should start with the rock type and then include other features such as sorting, grain textures, sedimentary structures, and fossils.

2. After you have completed your detailed stratigraphic column, interpret the sedimentary history of the area, starting with the Logan Formation at the base. Describe the depositional environments, briefly citing the evidence for each interpretation, and the possible events leading to each lithologic change.

At this last outcrop we are examining Pennsylvanian rocks well above the unconformity. We will concentrate on the unnamed siliciclastics at the base of the exposure and then walk up the road to examine the rocks there. Watch for fast-moving traffic exiting the highway.

1. Describe and interpret the sedimentary structures in the siliciclastic sequence at the bottom of this outcrop. Draw a scale diagram of one sedimentary structure here. What sort of depositional environment do these structures indicate?

2. Find the rock unit which is about 23 cm thick and near the top of the exposure (up the road towards the highway). What type of rock is it?

3. If you can find them, what sort of fossils are associated with this rock? (Either in the rock itself or above or below it.)

4. What depositional environment do you postulate for this rock? Consider the units immediately above and below it as well.