Paleontology and Finding Fossils:

It wasn't until hiking on the Colorado Plateau, specifically along a trail in the Grand Canyon, that the pursuit of Geology brought me face-to-face with Paleontology. The Grand Canyon (discussed extensively in my first book Spirit of the American Southwest) is a prime classroom for studying sedimentary rock and geologic time as told by the rocks. It is layer upon layer of sediment laid down by seas as they came and went during the Paleozoic Era (approx. 550 - 250 million years ago). The top layer, the youngest, over much of the Grand Canyon is called the Kaibab Formation. It formed about the time that North America was part of a huge continent, called Pangea (aka Pangaea). At the time, Pangea was the only continent on earth, surrounded by ocean. It was the end of the Paleozoic -- the Permian Extinction was imminent. Ninety percent of marine organisms were about to disappear. There was one last advance of the sea before the climate dried. The sea covered much of the Colorado Plateau area, a basin at the time. As sea creatures (marine invertebrates) died, their shells piled up at the bottom of the sea. The pieces eventually cemented together to form limestone. Then after many millions of years of erosion, along with periods of uplift of the Colorado Plateau, the fossilized limestone appeared as the Grand Canyon cap. Fossils of sea creatures are typically found in limestone formations and there it was, a beautiful specimen within the Kaibab Limestone -- a Brachiopod (above), over 200 million years old. My interests swung from Geology to Paleontology although both disciplines study fossil remains found in rock. The fossils are used to date and compare formations across the world.

Life evolves and fossils document the process:

To understand the evolution of life, a basic knowledge of the geologic time scale helps. Fifteen billion years ago, the Universe begins to form, then Earth takes its shape about 4.6 billion years ago. Water appears (from gases spewed by volcanic vents) surrounding small continents. Life was as barren as the land, mostly composed of single cell organisms. Then came an explosion of life in the water, called the Age of Fishes, the Paleozoic Era around 550 million years ago. Then the smothering extinction of 90% of marine life around 250 million years ago. Followed by the Age of Reptiles, starting 250 million years ago. First the amphibians came out of the water, then reptiles evolved. By the end of the Mesozoic Era, about 65 million years ago, the giant dinosaurs dominated life. But all died out during another grand extinction -- the Cretaceous Extinction. Mammals survived and dominated the final era, the Cenozoic. Paleontology can be pursued, as an amateur, by considering your era of interest. Most remains (fossils of flora and fauna) are found in limestone and other sedimentary rock, most are small sea creatures (invertebrates). The Colorado Plateau is a good place to start. Also, to be found on the Plateau are the remains of dinosaurs. If you start from the Grand Canyon, mostly Paleozoic Era rock, and move outward in any direction, you begin to encounter younger rock, the burial ground of the great dinosaurs. There are many locations in the west where dinosaur fossils, even their footprints, can be found. As mentioned in the Geology section, one of the most spectacular collection of bones is at Dinosaur National Monument, located on the northern borders of Utah and Colorado. When dinosaurs died, their bones were often swept up by floods and deposited in a central location, usually in a swamp, pond or lake. Over the years sediment is swept into the body of water covering the bones. The deposits harden, the lake dries up and millions of years later through erosion and uplift, the burial ground is exposed. At Dinosaur NM, they are exposed in one huge wall of rock (a cross-section of a former swamp) that stands almost three stories. Leg bones, the size of a man's body, and large vertebra protrude from the wall like great messengers of history.

If you're into reptiles, this is the place to start. As for mammals, their remains are scattered all over North America but because the geology of the west is so young, they are best exposed there. Utah has many sites with dinosaur finds and as you fan out from there, mammals appear in the younger rock strata and can be identified as camel, sabertooth tigers, small horses, strange looking beaver and giant mammoths, many of which have been found in the Ghost Ranch area of New Mexico. So, you can start at the oldest (billion year old) primitive, single cell organism fossil locations deep within the great gorge of the Grand Canyon (below) and end in northern New Mexico (Ghost Ranch and Clovis), where paleoindian spear points have been found well placed within mammoth and bison chest bones.

In John McPhee's book Basin and Range, he talks about how difficult it is for us to comprehend the lengths of geologic time in terms of millions and billions of years. Some geologists like to compare it to a calendar. The Precambrian Era extends from January 1st through the end of October. The Paleozoic Era consumes November and some of December. The dinosaurs (Mesozoic Era) appear in mid-December and die out in the extinction on Christmas Day. When do humans appear? McPhee says to hold your arms straight out. All of the above geologic time would run from one finger tip on your right hand to a finger tip on your left hand. If you scratched a nail on one hand with a file, the shavings would indicate human presence on earth.

Precambrian Era - 4.5 billion years to 550 million years ago.

Paleozoic Era - 550 to 250 million years ago.

Mesozoic Era - 250 to 65 million years ago.

Cenozoic Era - 65 million years to the present.

Hominids who walked upright (bipedal) - appear around 4 million years ago.

Earliest Homo sapiens, about 1 million years ago.

Ourselves, Homo sapiens sapiens, about 50,000 years ago, depending on which Anthropologist you talk to.

The Morrison Formation, the Dakota Formation, dinosaur and early humans:

Wherever you find the Morrison Formation of rocks, you'll find the great monsters of the Jurassic and Cretaceous periods of the Mesozoic Era. If you've ever traveled north from Phoenix, AZ up to the Colorado Plateau, which begins many miles south of Flagstaff, AZ, you'll drive through what geologists call the Transition Zone -- the zone that exists between the Basin and Range province to the south and the Plateau to the north. During plate collisions many millions of years ago, Himalayan-size mountains rose in that zone that cuts across the center of Arizona into western New Mexico. Eventually those mountains eroded and the debris remains were carried north by great rivers, all the way to the Dakotas (an excellent location for dinosaur fossils). The dinosaurs were caught in this sediment flow more than once and are best exposed at Dinosaur National Monument in a slab of rock which is the Morrison Formation. At Ghost Ranch in New Mexico, the Morrison can be seen about half-way up the tall cliffs that surround the ranch. Capping these cliffs is the Dakota Formation -- its sediment was accumulating when a great inland sea (called the Western Interior Seaway) cut North America in half, it ran from the Arctic to the Gulf of Mexico. The sedimentary rock of the Dakota Formation is another burial ground of the last of the great dinosaurs and it is also the marker for the time when a huge asteroid collided with earth, killing the dinosaurs. Most of these locations have wonderful trails. At Ghost Ranch (below) try the Chimney Rock trail and the Kitchen Mesa trail.

Please note: Ghost Ranch and its trails are thoroughly covered in my first book, Spirit of the American Southwest.

As the Western Interior Seaway pushed its shores to the west, it left the Dakota deposits at Ghost Ranch. Much of those deposits were sand, a hard sand composed mostly of Quartz. As it collected and hardened to rock, the Quartz sand grains fused to become Quartzite, a very hard rock and one favored by the earliest humans to the area, the Clovis People. Millions of years after the sea dried up and man appeared in North America during the Pleistocene Epoch (over 10,000 years ago), the hard Quartzite rock was favored for tools and weaponry. These lithic artifacts are now scattered all over the west -- at Archaeological and Anthropological sites and digs.