Ancient Families
To log this EarthCache, please send and email with the following information.
- List your first line as: Ancient Families: Walker Lake EarthCache GC4YG0J
- Estimate the thickness of the pre-Paleozoic Era fossils (the white layer)
- Describe the pre-Paleozoic Era fossils (the white ones)
- Estimate the thickness of the Devonian Period (grey layer)
- Describe the Devonian Period fossils.
- (Optional, but would be very helpful), Photograph the fossils you find.
Walker Lake has a very long history! The rocks in this location represent 8 geologic time periods covering almost 400 million years.
The Great Basin Desert covers the area south of Reno Nevada to Las Vegas Nevada. Early in Earth’s history before the Paleozoic Era, this area was an ocean floor. Life consisted of colonies of micro-organisms, corals, small simple clams and other marine life. Around 550 million years ago, life began to multiply and diversify. The first complex life forms started to show up and are found on the bottom layers of the exposed rocks at this location. These fossils are almost bleach white and are abundant in this location.
Plate tectonics isolated this location from the open ocean and it eventually became a freshwater shallow sea. Over the next 50 million years, the land continued to rise, the sea began to shrink and eventually disappear. Lush forest groves covered this land for the next 100 million years. About 400 million years ago, plate tectonics caused this lush, forest and grassland to sink again and become a shallow sea once again.
During the Devonian period, trilobites, fish and other complex sea creatures dominated this region. Those fossils can be found above the Paleozoic layer. These fossils are grey and not very well preserved. Isolated shells and parts of animal remains can be found scattered on the ground.
Little evidence remains from 400 to 250 million years ago, but fossils found from the Triassic and Jurassic periods (250-150 million years ago) can be found in isolated spots along this road. Very weathered bones and plants can be found preserved in dark limestone and sand beds near the top layers along the road. Plant and animal remains suggest this area was a savannah habitat with abundant food for large herbevores and the great predators.
Plate tectonics once again caused this location to become a sea again. Sediments suggest this sea was no more than 1000 feet deep for nearly 50 million years. The great K-T event 65 million years ago that killed the dinosaurs is very evident in many of the rock layers all along the lake and the road way. A thin, dark layer near the top is rich in iridium. There are very few fossils above this layer, suggesting this region once again rose above sea level.
During the last great ice age, this land once again underwent a massive climate change. The pressure of the massive ice sheets north caused the southern edge of the continent to rise, raising this region nearly 1 mile above sea level. The lush savannah environment, gone, replaced by arid cool temperatures.
About 10,000 years ago, when the great ice age finally ended, massive amounts of water rushed south, carving the great valleys and gouging the basins in the west. You are standing in one such river channel. Walker Lake next to you is a man made lake that has backed up water from the Walker River and is all that remains from that ice age river system.
Your task is to locate fossils from as many of the eras you can. Please photograph your finds and upload your pictures to help create a fossil record for others to enjoy and learn. If you can identify any of your finds, that is a bonus!
A very special THANKS to the Nevada Department of Transportation for allowing and encouraging this earthcache!