Rock Clues at the Wind Farm Visitor Center

The Two Slope Records

1A wind farm visitor center stands between North Slope and South Slope. During a trail survey, geologists recorded rock layers at both places. The layers were undisturbed, so a lower layer formed before the layers above it. Each record is numbered from the bottom up, so N1 and S1 are the lowest layers. The rocks at the two slopes are not the same thickness, but each record has four labeled layers.

2At North Slope, N1 is a sandstone with rounded pebbles and shell fossils from animals that lived in shallow salt water. N2 is a mudstone with freshwater snail shells and fish scales. N3 is a sandstone with rooted plant impressions and fern spores. N4 is a shale with the same two groups of shallow-salt-water shell fossils found in N1.

3At South Slope, S1 is a sandstone with shallow-salt-water shell fossils. S2 is a mudstone with freshwater snail shells and fish scales. S3 is a sandstone with rooted plant impressions and fern spores. S4 is a shale with shallow-salt-water shell fossils. The survey team recorded each fossil in the layer where it was found rather than making one list for the whole slope.

4The visitor center plans a panel about the changing landscape. The team wants the panel to show what the evidence supports without claiming more than the rocks and fossils can reveal. The report does not give the exact number of years represented by a layer or the precise size of the ancient water areas.