Page 50 - visitorGuide

■ Oil-Bearing Algal Structures
Algae have lived on Earth for billions of years. They range in size from sim-
ple, unicellular forms to giant seaweeds several meters long. Different algae
have different life cycles and physiological processes.This specimen was cut
through the center of limestone deposits produced by a colony of blue-green
algae. The algae lived along the shores of an ancient lake where sediments
were deposited.These would later become the oil shales of western Colorado
and eastern Utah. The dark stain is caused by oil trapped in openings in the
limestone. This specimen, part of the Douglas Creek Member of the Green
River Formation, is from algae beds near P.R. Springs, Utah, 110 km (70 miles)
south of Vernal near the Utah-Colorado state line.
Collected and donated by Michael Evetts and John Chronic.

■ Chalcedony in Petrified Wood
More than 40 species of fossil plants, as well as fossil fish, clams, amphibians,
and dinosaurs have been found in theTriassic Chinle Formation in and around
Petrified Forest National Park, Arizona. Most of the petrified wood is from
conifer trees that were distant relatives of today’s South Pacific Norfolk pine.
The conifers grew on nearby highlands, but they were carried by floodwaters
to the swampy lowlands and buried by silt, sand, and mud. Volcanic ash that
fell on the area provided silica to the groundwater that moved through the
sediments. Chemical reactions between the organic material in the wood and
the silica-rich groundwater resulted in the precipitation of chalcedony with-
in open wood cells and as a replacement of wood fibers. In some petrified
wood, the wood structure still remains, with original wood fibers locked into
the chalcedony that fills the cells.

■ Modern Solitary Coral
Coral is the hard, calcareous external skeleton secreted by
coral polyps for their support and habitation. Coral animals
live as individuals or as members of coral colonies or
reefs. This specimen, Fungia, is a solitary coral that lives
on or near reefs in many areas of the Pacific Ocean.

■ Fossilized Shark (Helicoprion) Teeth
This fossilized spiral of shark teeth, from the Permian
Phosphoria Formation near Soda Springs, Idaho, was
discovered in a phosphate mine. It came from the jaw
of an ancient shark that lived more than 280 million
years ago.The shark may have retained its younger
teeth, coiling them backward into and along its jaw
as newer teeth developed.
Gift from the Department of Geology, Idaho State University, Pocatello, through
H. Thomas Ore.

Native Copper

■ Native Copper
The shape of this slab of Precambrian native
copper, from the White Pine district in Michi-
gan, reflects the shape of the spaces that were
invaded by copper-bearing solutions about
1 billion years ago. Northern Michigan’s
Keweenaw Peninsula has yielded huge masses
of native copper weighing more than 450 metric tons
(roughly 1 million lbs).
Gift from the Copper Range Company, through Wayne S. Cavender.

40 VISITOR GUIDE