Desert Messenger

November 16, 2016 www.DesertMessenger.com 21 Potholes, arches, and really old critters ADVENTURES WITH ROCKS ™ www.RocksInMyHead.com The geology of Utah is amazingly di- verse. The layers of rock making up the state's landscape span hundreds of millions of years of geologic time. From the grayish mudstone and shale of the Wheeler Formation to the red and white layers of Navajo and Kay- enta sandstone, the rocks in Utah date from the Pre-Cambrian to Juras- sic ages. As one travels from west to east across the center of the state, the fl at expanses of Great Basin Des- ert butt up to the towering Wasatch Mountains, whose rugged peaks then give way to the candy-striped canyons and spires of the Colorado Plateau for which Utah is famous. A person traveling this route will experience over 500 million years of our planet's history in fewer than 250 miles. In the western part of the state, the ancillary, less rugged peaks of the House Range, in the Great Basin near Delta, are home to one of the best known Cambrian fossil beds in the world. Dating from about 550 million years ago, the Wheeler Shale within the Marjum Formation con- tains layers of shaley limestone and mudstone producing abundant tri- lobites. Fifteen separate genera of Trilobite have been identifi ed in the Wheeler Shale. The two most com- mon of the group are Elrathia kingi and Peronopsis interstricta. Elrathia is the most famous Wheeler Shale tri- lobite, and is quarried and sold to col- lectors all over the world. Prehistoric Great Basin tribes were the fi rst people to collect these fossils. Fossil trilobites have been discovered in Fremont archeological sites dating to 8000 years ago. In some instances, these specimens had been polished, drilled, and made into jewelry. The fi rst written account of the fos- sils found in this area of Utah is from Spanish missionaries in 1776. Early expeditions into western Utah were conducted by French and English fur traders and Spanish missionaries seeking to establish new routes to the west, and that fi rst written account of fossil mollusks and trilobites is found in the journal of the Dominguez-Es- calante expedition. The fi rst detailed scientifi c description and cataloguing of Great Basin fossils was published in 1845. Today, fossil enthusiasts from all corners of the globe travel to Delta to collect the world famous trilobites. On the other side of the Wasatch Range, Jurassic Period stra- tigraphy make up the landscape of Moab and the surrounding canyonlands. The fi ne-grained reddish- brown, white, or gray sandstones range in age from 250 to 65 million years old. It is within these layers that the arches, hoo- doos, slot canyons, and potholes known the world over are formed. Sediments from an ancient seabed, mixed with tiny grains of silica and compressed over time formed lay- ers known today as Kayenta, Navajo, and Wingate Sandstone. Geologic forces wrinkled and folded the rock creating cracks and fractures. Shifts and upheavals forced it to the surface where exposure to wind, water, and temperature eroded it into the beauti- ful formations we see today. Water carved deep slot canyons and potholes where cracks allowed a foothold, while wind eroded cliff faces and pinnacles into delicate arches and spires. It was this majestic and intriguing scenery that attracted explorers to the area in the early 1800s. Soon adventurers into the canyon- lands brought back reports of amazing formations, and the US Army Corps of Topographical Engineers felt com- pelled to lead mapping and scientifi c expeditions into the vast wilderness of southeastern Utah. In 1859, Captain John N. Macomb, a scientist Dr. John S. Newberry, and Paleontologist E.D. Cope were exploring a canyon south of present day Moab when they found parts of a front leg embedded in the sandstone. It was believed the leg was of a dinosaur and Dr. Cope named it Dystrophaeus viaemalae. Later they determined that the specimen was geo- logically the oldest sauropod dinosaur that had been found up to that time in North America. Since then, thou- sands of dinosaur fossils have been found in the sandstone formations of southeast Utah. Interestingly, it was not until fi fty years later that dinosaur fossils were found further east at the site which was eventually to become Dinosaur National Monument. Besides fossilized dinosaur bones, sandstone outcrops throughout southeast Utah contain footprints and trackways left by dinosaurs as they traveled through the Jurassic Period shorelines. Footprints are typically a few prints, while the term "track- way" is used to describe multiple prints in succession. Footprints are useful in determining the size, type, weight, and even age of the creature who made them. Trackways, on the other hand, present stories about di- rection, speed, purpose, stride length, and even number of animals present at the site which provide insights into dinosaur activities and habits. For example, by measuring the distance between tracks and determining the stride, a trackway can show if a di- nosaur was running or walking when that particular track was made. When visiting the Moab area, there are plenty of opportunities to see di- nosaur tracks within a short distance SEE POTHOLES PAGE 23 Food Handler Classes Food Handler cards are required for every person who handles or pre- pares food, and/or handles the eating utensils and food preparation equipment, including dishwashing. The cost is $15.00 per year and the card must be posted inside the food unit. Cards must be obtained prior to opening. Quartzsite, AZ: The Food Handler class and test will be given at: Quartzsite Senior Center, 40 Moon Mountain Road, on the following WEDNESDAYS: November 16- 10am & 2pm NOTE: Time changes in December and January DECEMBER CLASSES Dec. 7th and 14th 9am and 10:30am JANUARY CLASSES Jan. 4th, 12th and 18th 9am and 10:30am Note: If you need a Spanish video and test, please contact the Health Department at 928-669-1100. Spanish classes are available in Parker at the Health Department, 1112 Joshua Ave., #206, on Mondays and Wednesdays from 7:00 am - 4:00 pm. Dinasaur Ridge Trackway

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