Page 34 - 2008 DT 12 issues

Out of the Pits 100 tar pits have yielded an unprec-
edented assortment of predators and
n the heart of Los Angeles lies a prey, large and small. More than one
portal to another world. Occupying million fossils representing 50 mammal
Ijust a couple of square blocks along species, 125 types of birds, and dozens
Wiltshire Blvd., Rancho La Brea is, never- of reptiles, insects and other inverte-
theless, one of the largest and most famous brates have been recovered. Remarkably
Ice Age fossil sites in the world. Its tar preserved disarticulated skeletal com-
pits have produced the most diverse as- ponents of entire animals have, in some
semblage of plant and animal fossils ever cases, included even the bone marrow.
found—over one million fossils since In 1901, geologist William Orcutt
1908, representing 650 species of ani- uncovered a small armored segment
mals and plants that populated the area of a ground sloth’s hide. With further
between 10,000 and 40,000 years ago. excavation, he soon had a complete Dire Wolf skeleton
The first written documentation of skull of a sabertoothed cat, along with a
the tar springs was made in 1769 by treasure trove of other fossils. Although in Venezuela have barely begun,
extensive excavations have they are yielding astonishing results.
been made at the La Brea site, Known since the 16 century, but
th
it is Pit 91—measuring 28’ largely ignored, the Venezuelan seeps
by 28’ and 14’ deep—that has are found in a variety of ecosystems
contributed most of the fossils, and so may hold a wider variety of
including more than 3,000 dire creatures. Because the sites are near
wolves, more than 2,000 saber- where the Isthmus of Panama joins
tooth cats, as well as coyotes, South America, their fossils may reveal
camels, bison, horses, and even information about migrations of animals
mastodons. In 2000 alone, more and plants to or from either continent.
than 1,600 fossils were recov- One Venezuelan site, Inciarte, is
ered, mostly mammals and more than a kilometer long and 500
birds. Also recovered
A La Brea Tar Pit were 90 plant fossils,
Juan Crespi, a Franciscan friar with 6 seeds, and 62 rocks.
the Spanish expedition of Gaspar de Carnivores represent about
Portola. In Spanish, “brea” means 85% of the animal fossils at La
“tar.” At the foot of the Santa Monica Brea, and meat-eating birds,
Mountains lay a grass covered alluvial 70% of the avian species, lead
plain about 45 miles in circumference. by eagles. These ratios are puz-
In the center were about 20 acres of tar zling, given the known ratio of
vents and sandy, bubbling black puddles predators to prey. Eagles, for
that hardened at the surface into small example, are relatively rare com-
mounds. Toward the center of the field, pared to other bird species, yet Harlan’s Ground Sloth
however, the asphalt remained soft and are abundantly represented here.
semi-fluid. The tar springs and asphalt Were the large predators lured by the meters wide, at least 10 times the size
seeps were well known to the local site of struggling prey mired in the tar? of the tar pits at Rancho La Brea. It has
Indians, who used the tar to seal their Thousands of sites in Southern already yielded the remains of more than
canoes and to attach handles to blades. California duplicate the stratigraphy 100 species, including 43 mammals, 56
But it wasn’t until 1828 that the land was found at La Brea, yet only a few have birds, 11 lizards, and 4 frogs. A dozen
exploited for its bubbling black ooze. yielded substantial numbers of fossils. or so of the fossils belong to bats and in-
Since 1865, when the first fossils By contrast, although excavations of clude skulls, jaws, teeth and a humerus.
were excavated from the tar, La Brea’s similar petroleum seeps, or menes, Because the Inciarte tar was covered by
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