TV Show "La Brea" Inspires My Report On Mojave Desert Ice Age Fossils

[Inyo]

"La Brea" time travelers find a Mojave Desert man who fell into their Pleistocene zone. That inspired my fossil report:

Perhaps it is difficult to picture, but some 450,000 to 18,000 years ago a great fresh water lake covered roughly 83 square miles of the present-day Mojave Desert in southern California. This was ancient Lake Manix, some 200 feet deep at its highest stand, created by a combination of flood waters from the ancestral Mojave River and an increase in precipitation during an interglacial period of the Pleistocene Epoch.

Today, the remains of 21 species of mammals and 25 species of birds can be found in the sediments deposited in that relatively long-lived body of water--in addition to abundant ostracods, freshwater mollusks, and skeletal elements from a fish--the Tui Mojave Chub.

Geologists call the Late Pleistocene sediments that contain those fossils the Manix Formation, an Ice Age remnant which now yields an important diversity of nicely preserved vertebrate and invertebrate specimens that provide invaluable information on the historical geology of the Mojave Desert district.

The Manix Formation of San Bernardino County, California, has yielded one of the most significant fossil faunas of Late Pleistocene mammals and birds on the West Coast. Many of the species identified have also been recognized in the world-famous La Brea Tar Pits in Los Angeles.

In addition to the mammals and birds, several other varieties of animal life have also been recovered from the sediments of Ice Age Lake Manix. These include five species of ostracods, two species of fresh water pelecypods, nine species of fresh water gastropods, two species of fish (the Tui Mojave Chub and Three-spine stickleback), and one species of reptile (the Western pond turtle).

Most of the fossil bones have been collected from a narrow three-foot zone in the middle of the formation, vertebrate specimens dated by the Uranium-Thorium equilibrium method at 290 thousand years old. Two additional bone-bearing horizons also occur in the Manix Formation, although they yield far fewer specimens than the older zone. One lies a few feet above the main bone bed and has been dated by the Uranium-Thorium radiometric technique at 195 thousand years; the second is found throughout the uppermost 20 feet of the Manix Formation in strata approximately 60 to 19 thousand years old.

Two more age-constrained beds of fresh water mollusks also occur throughout the Manix Formation. The older zone yielded a Carbon 14 result of 49 thousand years, while the younger shell horizon, also dated by the famous Carbon 14 radiometric age method, was determined to be 19.1 thousand years old.

Some 25 varieties of fossil birds have been identified from the Late Pleistocene section, including such extinct forms as the Large-footed Cormorant, the Brea Stork, the Small Flamingo, Cope's Flamingo, Shufeldt's American Coot, and the Oregon Gull; living members of the avian fauna include the Arctic Loon, Eared Grebe, Western Grebe, American White Pelican, Double-crested Cormorant, Tundra Swan, Honker, Green-winged Teal, Mallard, Greater Scaup, Common Merganser, Ruddy Duck, Bald Eagle, Crane, sandpiper, a phalarope, a large gull, Golden Eagle, and the Great Horned Owl.

In analyzing the variety of bird fossils in the Manix Formation, it is germane to note that 96 percent of the specimens are considered waterfowl. Also, two-thirds of the living members of the fauna presently prefer to feed exclusively on small fish. From this line of evidence, it appears probable that the Tui Chub represented in the fossil record here provided a substantial diet for many of the birds at Lake Manix.

The life habits of living members of the fossil bird assemblage show that the primary Late Pleistocene habitats included open water, sandy beaches and abundant reedy marshlands. Many extant representatives of the fossil bird fauna range at present throughout southern California and can be found seasonally on the Salton Sea and other inland bodies of water; several living species prefer coastal marine conditions or inland areas in the San Joaquin Valley of California.

Among the 21 species of mammals identified from the Manix Formation, the following extinct types can be recognized: a medium-sized ground sloth; the Shasta Ground Sloth; a large ground sloth; a mammoth; the Dire Wolf; a short-faced bear; a scimitar cat; the Western Camel; the Minidoka Camel; a Large-headed llama; an Antique (Ancient) Bison; the small Mexican Horse; and a large Western Horse. Living members of the mammalian fauna include a jack rabbit, a mouse, Coyote, a bear, Puma, Pronghorn, and a Bighorn Sheep.

Plant remains in the Late Pleistocene beds are rare, but a few poorly preserved specimens have been encountered, mainly carbonized wood and leaf fragments that have not appreciably helped to determine the kind of vegetation that once existed here.

In an attempt to better understand the Ice Age vegetation of Lake Manix time, paleobotanists have also analyzed the plant remains in packrat middens that date from the Late Pleistocene. Based on the fossil gatherings of such rodents in southern Nevada, Arizona and southeastern California, there is convincing evidence to suggest that modern-day woodlands now restricted by altitude were some 3,000 feet lower during deposition of the Manix Formation. This means that Pinyon pine and juniper, presently kept to a regional minimum elevation of 5,850 feet, were in all likelihood thriving at 2,600 feet 200 thousand years ago in the neighboring Alvord, Cady, Calico and Newberry Mountains. Today these mountains are practically barren of any kind of vegetation.

From the available evidence, it appears that juniper, sagebrush and creosote brush covered the alluvial slopes surrounding Lake Manix. Slightly higher elevations supported a Pinyon pine-juniper-evergreen live oak woodland, while white fir likely formed a dense forest in the Newberry and Ord Mountains at an altitude of 3,950 feet; present-day conditions keep white fir a a minimum elevation of 7,150 feet. Bordering the lake were marshlands that probably supported reeds, rushes, pondweed, duckweed and cattails. Patches of grasslands certainly existed in the drier flats, much like they do in present-day regions characterized by a similar pine-juniper-oak woodland.

Today, the luxuriant growth of Pleistocene plants has vanished. In their place is an extensive barren badlands of pastel sediments which yield a wealth of fossils. The most commonly encountered mammalian remains belong to the Western Camel (the George C. Page Museum of La Brea Discoveries in Los Angeles has an excellent skeletal reconstruction), the Large-headed llama, the large Western horse, the Mexican Horse and the mammoth. Among the birds--whose hollow, delicate bones are miraculously well preserved in the Manix Formation-- the most frequently reported species include the Western Grebe, the Small Flamingo, The American White Pelican, and the Honker. Specimens of the Tui Chub and Three-spine stickleback, while found scattered throughout the fine silts and sands of the upper half of the Manix Formation, are often concentrated in the middle of the sedimentary section in strata roughly 290 thousand years old.

Also living in ancient Lake Manix were numerous gastropods and pelecypods. Such mollusks are among the most abundant fossil forms found in the Late Pleistocene section. The two widespread beds crammed with well preserved snails and clams occur near the top of the formation in distinct zones about 18 feet apart. Their original shell material has been preserved intact, although it is extremely brittle.

Both mollusk-bearing beds yield a bewildering mixture of species that, individually, prefer different fresh water habitats--such as rivers, streams, ponds, lakes, bogs and swamps. Apparently this unusual assemblage of snails and clams resulted from deposition due to flooding. Mollusks from every local habitat were jumbled together by the rising waters of Ice Age storms, then transported and dumped into the reaches of Lake Manix by engorged streams.

Today, when visiting the 450 to 18 thousand-year-old Manix Formation (presently part of Mojave Trails National Monument), take some special time to enjoy the view afforded. Below is stark desert, a blistered region of subdued hues, a harsh and unforgiving landscape where vegetation is scarce and visible animal life apparently nonexistent.

That a great Ice Age lake once covered this land seems improbable, but the fossils in the sediments prove the case--that 19 thousand years ago you would have seen flamingos, pelicans, ducks, eared grebes, gulls, storks, cranes and loons swimming and wading in Pleistocene Lake Manix, a vast 83 square miles of pristine glacier-fed waters that teemed with fish for the hungry birds. Above the lake would circle Bald Eagles and Golden Eagles and Great Horned Owls--large predatory birds, raptors, ready to seize the unwary in their powerful talons.

Amid the surrounding countryside a Shasta Ground Sloth might be seen leisurely browsing on the upper branches of a juniper tree; a pack of hungry Dire Wolves is cutting off a large Western Horse from the herd; and a scimitar cat has just brought down a baby mammoth on a open grassy plain. There is blood gushing from the punctured jugular and the vulturous condors soar high above.

In the distance, a violent storm is developing, a storm that will create a rushing flood of waters destined to sweep along the carcasses of both mammals and birds to the momentarily placid lake; there, the bones will be covered by fine silts, sands and clays, to remain hidden for some 19 thousand years until they are seen for the first time by human eyes in the middle of a great desert.


A metapodial from an extinct Western camel; Manix Formation, about 19,000 years old.

[Inyo]

Just a supplementary observation on the inaccurate botany portrayed in the new television program "La Brea," where numerous Los Angeles folks in the immediate vicinity of the La Brea Tar Pits fall into a mysterious sinkhole and instantly find themselves at the La Brea Tar Pits in 10,000 BC--that is to say, 12,000 years ago during the latest Pleistocene Epoch (at least one unfortunate individual is transported to their locality from an apparently related sinkhole on California's Mojave Desert).

But there's a geographic problem. In actual fact the show is shot in Australia, a rather dubious decision that obliterated all opportunity, save through prohibitively expensive additional computer generated imagery--the special effects extinct Pleistocene mammals created with cgi have thus far been impressively impactful (a dire wolf, a saber tooth tiger, camels, a giant ground sloth, and a giant bear)--to achieve at least a modicum of late Pleistocene age vegetational verisimilitude.

A natural caveat of course is that no place on Earth today bears a botanical biota identical to Los Angeles area late Pleistocene-age plant communities. At that rather recent date (geologically speaking), for example, you had Coast redwoods living in proximity to sagebrush, in addition to several exotic species no longer found in North America--most notably, perhaps, a juniper (Juniperus cf. J. barbadensis), now native to the Bahamas, Cuba, Jamaica, and Saint Lucia.

Nevertheless, the closest modern-day geographic and associated Ice Age-environmental counterpart to LA's late Pleistocene botanic scene would be around Monterey, California, approximately 315 miles north of the La Brea Tar Pits, near where Coast redwoods now live, gymnospermous conifers that would have extended southward to Los Angeles during a period of optimal late Pleistocene climatic conditions.

Here's an abbreviated list of botanical specimens secured from the late Pleistocene La Brea Tar Pits, focusing for the most part on tree species described--excluding, therefore, many varieties of diatoms (microscopic single-celled photosynthesizing organisms usually allied taxonomically with algae, though older floral lists sometimes continue to categorize them as plants), grasses, sedges, heathers, perennials, stonewarts, pondweeds, and annuals, among others):

Pinus muricata Don (bishop pine)
Pinus radiata Don (Monterey Pine)
Pinus sabiniana Dougl. (digger pine)
Sequoia sempervirens (Lamb) Endl. (Coast redwood)
Cupressus forbesii Jeps. (Tecate cypress)
Cupressus goveniana Gord. (Californian cypress )
Cupressus macrocarpa Hartw. (Monterey cypress)
Juniperus cf. J. barbadensis (a juniper now native to the Bahamas, Cuba, Jamaica, and Saint Lucia)
Juniperus californica (Carr.) Antoine (California juniper)
Juglans californica S. Wats. (California black walnut)
Salix lasiolepis Benth. (arroyo willow)
Celtis reticulata Torr. (hackberry)
Alnus rhombifolia Nutt. (white alder)
Quercus agrifolia Nee (coast live oak)
Quercus dumosa Nutt. (Nuttall's scrub oak)
Quercus lobata Nee (valley oak)
Berberis sp. (barberry)
Umbellularia californica Nutt. (California bay)
Platanus racemosa Nutt. (Western sycamore)
Rubus vitifolius Cham. and Sch. (California blackberry)
Toxicodendron diversiloba Torr. and Gray (Pacific poison oak)
Acer negundo L. (box elder)
Rhamnus californica Esch. (California coffeeberry)
Cornus californica C. A. May (dogwood)
Ceanothus sp. (California lilac)
Artemisia sp. (sagebrush)

[Big Band Guitar]

One big glowing error is a wedding ring of gold can not be carbon dated. There is no carbon in a gold ring.

[Gdjjr]

Interesting reading. IF, I could go back in time, knowing what I know now, I would study anthropology- fascinating stuff to be learned from the past.