Fossil Provides Center Piece for a Carmel Home

Posted by Ben Licari on Mar 18, 2015

Gar Fish Fossil (Lepisoteus simplex) from the Eocene Epoch, approximately 50 million years old 

Customer Delights at Discovery

Graniterock sells hundreds of different natural stones from all points of the globe. Most of the natural stone comes from the United States and some of the stone is clearly sourced from very specific locations. As with all things in nature, serendipitous discovers are often a delight. So was the tale of a beautifully preserved fish fossil found in a palette of stone delivered to a Carmel, California job site and eventually affixed to the center focal space on a beautifully remodeled natural stone fireplace in that home.

Graniterock gets many requests for light-colored stone reminiscent of the native stone used in the area for centuries. It is often referred to as Carmel Stone or Monterey Stone. The true stone is no longer harvested in the area and Graniterock has sourced a number of products that are equal to, and better, in many cases. One such stone is known as Monterey Cream.

This is the stone that yielded the ancient fossil. The contractor was observant enough to realize this specimen had to be put in a prominent location, which he did. He then sealed the stone, as it is close to a diatomaceous earth, and needed to be sealed to prevent permanent staining. When the sealant was applied the beautiful fossil miraculously turned a wonderful blue hue.

Word got back to the Robin Steudler, the Graniterock Account Manager responsible for the original sale. Robin thought finding out just how old the fossil was, and what type of fish created it, would make for a very interesting story. Robin contacted one of Graniterock’s Geologists, Ben Licari, and his research resulted in the following report. 

Green River Formation

The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and represents one year. The sediments of the Green River Formation present a continuous record of six million years. The mean thickness of a varve here is 0.18 mm, with a minimum thickness of 0.014 mm and maximum of 9.8 mm.

The sedimentary layers were formed in a large area named for the present-day Green River, a tributary of the Colorado River.  The area of the formation exists as three separate basins around the Uinta Mountains of northeastern Utah; the largest area, in northeastern Utah and western Colorado south of the Uintas, known as Lake Uinta.

Lithology and formation

The formation of intermontane basin / lake environments during the Eocene resulted from mountain building and uplift of the Rocky Mountains.  Tectonic highlands supplied the Eocene sedimentary basins with sediment from all directions: the Uinta Mountains in the center; the Wind River Mountains to the north; the Colorado Rockies to the east; the Uncompahgre Plateau and the San Juan Mountains to the south and finally, the Wasatch Mountains of Utah and the ranges of eastern Idaho to the west.

The lithology of the lake sediments is varied and includes Sandstones, mudstones, siltstones, oil shale, coal beds, saline evaporite beds, and a variety of lacustrine (lake) limestone and dolostone.  Volcanic ash layers within the various sediments from the ten active Absaroka Volcanic field to the north in the vicinity of Yellowstone and the San Juan volcanic field to the southeast provide dateable horizons within the sediments.   The Green River Formation is the type locality for eight rare minerals and 23 other valid mineral species.

Within the Green River Formation of southwest Wyoming in the area known as Fossil Lake, two distinct zones of very fine-grained lime mud deposits are particularly noted for preserving a variety of complete and detailed fossils.  These layers are an Eocene Lagerstätte, a rare place where conditions were right for a rich accumulation of undisturbed fossils. The most productive zone—called the split fish layer—consists of a series of limey mudstone about 6 ft (1.8 m) thick which contains abundant fish and other fossils. These are easily split along the layers to reveal the fossils. This thin zone represents some 4000 years of deposition. The second fossil zone, the 18 inch layer, is an unlaminated layer about 18 in (46 cm) thick that also contains abundant detailed fossils, but is harder to work because it is not composed of fissile laminae.

The Green River fossils date about 50 million years ago (mya), but cover several million years, including the transition between the moist early Eocene climate and the slightly drier mid-Eocene. The climate was moist and mild enough to support crocodiles, which do not tolerate frost, and the lakes were surrounded by sycamore forests.

The source for our Monterey Cream is a quarry in central Utah.  The deposit is located right in the center of the Eocene Lake Uinta.  The following maps show the location of Lake Uinta.

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