A brief history of time
VIC LEIPZIG AND LOU MURRAY
Ever since Vic and I moved here, I’ve been trying to make sense of
the fossil record of Orange County. When I lived in Colorado, the
fossil fuss was over dinosaurs, but it seems that all we ever hear
about here in Orange County is fossil fish, whales and sharks.
At the La Brea Tar pits in Los Angeles, the focus is on mammals of
the Pleistocene epoch, a time period that spanned from 1.8 million to
10,000 years ago. That’s where I first learned about the
saber-toothed cat, dire wolf, giant sloth and ancient bison. These
over-sized animals, along with mammoths and mastodons, roamed the
ground where we currently live. In fact, fossil remains of ancient
bison and mammoths have been found on or near the Bolsa Chica mesa.
The questions that bug me are why are there no dinosaur fossils in
Orange County, and what happened to the giant mammals of the
Pleistocene?
It took a trip back to Colorado last week with my cousin Laura
Klure to finally make sense of it all. On our long drive, we talked
about geologic time periods, evolution, Pleistocene gigantism and the
possible causes of extinction of those marvelous beasts. OK, maybe
you wouldn’t have wanted to be along on that trip, but we had fun.
We stopped at the Museum of Western Colorado in the tiny town of
Fruita, hoping to pick up some information. As we entered the museum
through a rock tunnel, we were greeted by grunts, growls and roars
coming from a huge hall filled with animatronic dinosaurs. Everything
moved. A top-heavy triceratops stepped menacingly toward us. A
vicious Utahraptor shook the bloody head that it had just ripped off
a long-necked dinosaur. But the real fun was when we narrowly avoided
being soaked by a spitting dilophosaurus.
This museum in the middle of nowhere was a fabulous surprise, but
its focus was clearly on the Cretaceous period of 144-million to
65-million years ago, not the more recent Pleistocene epoch. There
wasn’t a mammal in sight.
It took a visit to a rock shop in Nederland, Colo. to make it all
clear. There I found a laminated poster called “A Correlated History
of the Earth.” It went back 4.5 billion years to Earth’s formation.
It had different columns for movement of the land masses, names of
the geologic eras, periods and epochs, times of major meteor impact
craters and approximately when major plant and animal groups
appeared. I figured that this poster with its microscopic type wasn’t
one of their best sellers, but I snapped it up.
After studying the poster and searching the internet, I’ve finally
figured out what every school child in town probably already knows.
There were no dinosaurs in Orange County because the land was
underwater during the time when dinosaurs lived. Thus Colorado has
dinosaur tracks and bones and Orange County has marine fossils, as
well as more recent Pleistocene mammal fossils.
A huge meteor impact on the Yucatan Peninsula about 65-million
years ago is thought to be what put an end to the Age of Reptiles.
Mammals evolved, diversified and took over the ecological niches
occupied by the dinosaurs. All this time, the land masses were moving
on great tectonic plates. About 25-million years ago, the land that
we live on now was not only underwater, it was south of us around
what is now Ensenada, Mexico. With the formation of the San Andreas
fault, the land west of the fault moved northward a bit with each
jolting earthquake until it got where it is now.
About five million years ago, during the time period known as the
Pliocene epoch, the Santa Ana Mountains began to uplift and the Santa
Ana River deposited huge masses of alluvium that would become the
land of Orange County. During the end of the Pliocene and beginning
of the Pleistocene 1.8-million years ago, the land continued to rise
out of the ocean, exposing a series of marine terraces. You can see
evidence of those terraces today if you drive along Warner Avenue
toward the ocean.
The time of the Pleistocene ice ages was also when huge mammals
evolved. There are a lot of theories about why there were larger
species then. A radiation event may have caused the gigantism of the
Pleistocene, nutrients may have been more readily available, the cold
weather may have been a factor, or we may simply be in a period of
relatively dwarfed animals now.
Saber-toothed cats, our official state fossil, were one of the
huge mammals that roamed over our area. These cats were the size of
African lions, but were much heavier and had short tails like
bobcats. Like African lions, they lived in prides, but unlike African
lions they were more likely to stalk their prey than chase it. They
used their seven-inch-long canine teeth to rip open the bellies of
their prey. Now these beasts that existed for hundreds of thousands
of years are gone.
With the dramatic change in climate that ended the ice ages, the
large mammals of the Pleistocene disappeared from earth forever. The
arrival of humans with their advanced hunting skills or the loss of a
keystone species due to disease may have played a role in their
disappearance as well.
Now we are poised on the brink of another dramatic global shift in
climate. Ideally, we will learn from the past so that we can better
plan for the future.
* VIC LEIPZIG and LOU MURRAY are Huntington Beach residents and
environmentalists. They can be reached at vicleipzig@aol.com.
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