Day 6: Specimen Ridge Petrified Wood, Creationism, Waterfalls, Volcanism…and More

Petrified Forest Site Up on a very steep ridge Consists of 27 layers of many buried forests Located near a glacial basin with a river flowing through it What is petrification? How is it different from fossilization and replacement?

What We Were Looking For Vertical stumps Log Alignment Sedimentary structure Types of Trees Roots, Branches, Leaves, etc. Ripple Marks and indications of flow >> These all give indications of how petrification occurred.

What we Found Vertical stumps, horizontal logs and one instance of both combined. No alignment; very few horizontal specimens MSC found; sandstone found around roots. We don’t know what types of trees were petrified. Large root system found. Some branches found. Small indications of cross-bedding. No other flow marks found. So some trees were most likely transported in a mud flow or similar event; some may not have been.

Dating Method Older Method Carbon 14 Cosmogenic Life Relative Dating

Erosion of Trees Tree on hill - outside petrified, inside eroded Outside could be mineralized first, inside more slowly; not as stable so erodes quickly –Could be from inside rotting, not completely petrified –Animals live in root holes, also help to erode Explains the erosion gradient; couplets of rings –Light ring petrified, dark not –Could be wood (50million yrs old)

Waterfalls Recall the changing nature of rivers Base level rise Base level drop

Relative Dating and the Canyon Rhyolite deposits from Dave’s speech Dike intrudes; younger than the deposit Fault line; younger than the dike Top layer usually sedimentation This allows for relative dating

Application to the Canyon Radioactive dating- two different ages on different sides of the canyon Broad valley- lava flow into it; thick Rising of river- eroded part of valley and retreated –Three river valleys New basalt and gravel flow fills in other side –Discussed possibility of two different lava flows (relatively same dates) –Glaciation on top

Hoodoos Towers of rock, usually along a riverbed Formed with a erosion-resistant rock cap Column of more erodable rock beneath it is shielded by the tough rock cap by the river Can also be eroded by wind instead of water

Merry Yellowstone Christmas!