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 [email protected].