At home, my reading confirmed that the shells I saw are from the Cretaceous period, million years ago. During the Cretaceous period, all of Europe and half of North America were submerged in water. The North American seaway ran from the equator to the Arctic and was about meters deep. Most geologists also believe that North America was attached to Europe during this era Lambert. The shells I saw are clam-like shells that could be "pelecypods" Ratkevich.
The pelecypods probably fed off of blue-green bacteria or blue-green algae. Although the seaway, like the pelecypod, is long gone, blue-green algae survive today, alongside the White Cliffs trail, in cryptobiotic soil. Cryptobiotic soil forms where blue-green algae bind sand grains together. This keeps soil in place and prevents erosion. Cryptobiotic soil also helps to attract potassium and calcium, minerals fostering plant growth.
Cryptobiotic soil, then, is very important in a desert ecosystem. I have heard that it can take cryptobiotic soil anywhere from 50 to years to recover from one footstep. I will certainly avoid walking on any when I go off-trail. I looked for fossil cephalopods on White Cliffs trail, but I have found these spiral fossils only at a road cut in McGaffey National Forest, about 20 miles southeast of White Cliffs Figures A close look at Pyramid Rock revealed several layers of rock.
Since new layers of rock build on top of old layers, younger layers usually top older layers. However, faults and weathering rearrange and wear away rock, and some rocks, such as sandstone and limestone, are more resistant than shale and mudstone.
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At Pyramid Rock, Orange Wingate Sandstone Figure 10 represents the remains of a vast Sahara-like desert, formed during the late Triassic or early Jurassic era geologists are not agreed on the exact era. The next layer is Jurassic Entrada sandstone. The shells I found are from the Dakota Sandstone layer.
Before reaching White Cliffs, we saw to the east the ruins of an old coal mining operation. Coal forms when plants die in wet, acid conditions. Instead of completely rotting, the plants turn into soft, fibrous peat. Overlying sediments drive out the moisture and squash the peat, making it lignite, or soft brown coal. Greater pressure creates bituminous coal, which is harder, blacker, and has an even-higher carbon content.
This coal is hard, black and shiny, and has a higher carbon content then any other stage of coal. Coal is rich in carbon because it is made of plants. Most coals are remains of low-lying forests drowned by invading seas and buried under sediments. Coal in our area is Cretaceous in origin Lambert. Surrounding the White Cliffs are hogbacks, formed by steep, even-crested ridges. Hogbacks, common to the southern Rockies, form when the layers of rock dip sharply. They have steep slopes and a bed of resistant rock. But surrounding the resistant rock is a bed of easily eroded rock Lambert. Today I returned to the seashore.
I hoped to observe the plants and wildlife near the shells, as well as to find and photograph some new and more unique fossils. This time the flowers had all wilted and dried up. Only a few yuccas had blossoms. The flowers were wilted and their stems broken. We saw yucca fruit that had fallen off the plant. The cacti were bare. Cacti are harder to notice without their blossoms. This time we were not greeted by chirping cicadas.
Instead, we saw their skins. There were many skins on the ground, as well as skins attached to bushes and trees Figure We even saw several yuccas that had cicadas attached to them. We noticed some shells earlier than we had last month. We must have thought that they were just ordinary rocks mixed in the dirt, but this time we noticed right away that they were shells. But we didn't find any interesting fossils until we came to the main deposit.
We found two interesting fossils. One was an imprint of a small ruffled shell; the other was an imprint of a leaf Figures I had not found any other fossils like them before. From my reading, I think that the fossils are from the Cretaceous period, about million years ago. During this time much of Europe and about half of America were submerged in water. It is hard to imagine so much of the world covered in water.
On June 24, I was surprised at how dry it was. But it was dry because there was no rain or melting snow to feed the plants. In May, melting snow fed the flowers that bloomed alongside the trail. By June the snow was gone, but the summer monsoons had not yet begun. Throughout the Cretaceous era, ferns and coniferous trees grew here.
But at the close of the Cretaceous era, an important phenomenon occurred: plants flowered. This was a new development Fortey. I found the leaf imprint in a gully where it had washed down.
This fossil is probably from the topmost layer of the Dakota Sandstone and washed down with melting snow. The development of flowering plants during the latter part of the Cretaceous era is significant because it happened as other life forms reached extinction. The grasses and flowering plants that first appeared in the Cretaceous time flourished into the Tertiary period! Today we walked on White Cliff Road to visit the gully with the fossils.
It was sunny but not too hot. The rabbit brush and sage are still growing although the rabbit brush will seed soon. This way, the rabbit brush does not have to compete with its more colorful rivals to be pollinated Figure The beautiful mountain area is dense with trees, bushes, and shrubs including pine, oak, elm, and poplar. Geology of the Sacramento Mountains, compiled from several sources and field observation is mentioned briefly below. East of the Sacramento Mountains is the Great Plains.
The faulted blocks of the Basin and Range were formed by the extension of the crust in the past 65 million years. Geologists believe this part of the area, the Tularosa Basin, was formed from the downthrown block from the crustal extension of the Rio Grande Rift Zone which began approximately 28 million years ago Seager, et.
The strata in the Sacramento Mountains dip gently from west to east. Residents in the Artesia, New Mexico area obtain water that rises through the wells without the use of pumps Halka, The sedimentary layers are mostly massive limestone layers of the San Andreas Figure 5 and sandstone and shale of the Yeso Figure 6 Formations.
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Gypsum layers are also exposed at few places. These formations were deposited in the marine environment during the Pennsylvanian and Permian Periods about ,, years ago. Travelers will find sedimentary rocks are sparsely exposed due to the dense vegetation in the area. However, they can observe excellent exposed rock formations along the roads and hiking trails, all within 20 miles radius of Cloudcroft. Many places along the roads and trails do have markers describing geology and rock formations at the observation points.
Travelers should stop at Tunnel Visa at US 82, just west of High Rolls to observe excellent view of Pennsylvanian and older sedimentary rocks and faults see Figure 7. In several places where the limestone layers are exposed, the travelers expect to see abundant fossils such as brachiopods Figure 9A , ammonoids Figure 9B , crinoids Figure 9C , fusulina Figure 9D , and corals Figure 9E.
Not shown in photos, bryozoans, gastropods, pelecypods, and cephalopods can also be found in the exposed limestone layers. The area within mile radius of Cloudcroft is truly an excellent hunting ground for fossil hunters and rockhounds. Cloudcroft residences like to pick fossils for their home or landscape decorations.
For example, the golf course at the Lodge has limestone boulders around the fairways as parts of the landscapes. Golfers should take the time and check out the boulders for ammonoid and brachiopod fossils Figure Geologists believe the southern part of the Sacramento Mountains and the surrounded area were part of the marginal marine to marine environment during much of the Pennsylvanian to Permian Periods Figure The events occurred about million years ago see SE NM in. The kind of the depositional environment and climate is believed to be similar to the present day Great Barrier Reef, just north of Australia or the Bahamas Islands east of Florida.
Mountains such as Appalachian and Ancestral Rocky Mountains appeared. During late Permian to early Triassic, the western part of North America and South America was uplifted to become land mass and the Pedernal Uplift around Cloudcroft were born. Note: Pedernal Uplift is not the same mountain range as the Sacramento Mountains. Pedernal Uplift appeared during Triassic to Cretaceous Periods.
The Sacramento Mountains formed as faulted block from event during the formation of the Rio Grande rifting. Figure 4 shows most of the Sacramento Mountains lack sedimentary rocks of the Triassic to early Cretaceous Periods pre-Dakota in the north central part of the geologic map in Figure 4.
Geologic Map of New Mexico
Dinosaurs are thought to roam the area. The Dakota Group Kdg in Figure 4 is made up of sandstone, shale, and coal? Geologists believe approximately 85 million years ago the area was undergoing subsidence from the compressive stress when the western part of the North American Plate was going over the Pacific Oceanic crust. The post-Dakota strata may have been deposited but were eroded away during the Cenozoic Era. Geologic map also shows few small intrusions of magmatic origins Ti in Figure 4 in the western part of the Sacramento Mountains.
Roadside Geology of New Mexico
Allen , however, prepared interesting report about Lake Otero just east of Alamogordo in the Tularosa Basin that occurred during glacial time 45, — 28, years ago. Thus the pluvial lakes were formed at the time during the glacial stages when the climate was moist from heavy precipitation. Perhaps, the meltwater from the glaciers or heavy snow in the surrounded mountains Sacramento and San Andres dissolved and transported gypsum into Tularosa Basin forming Lake Otero.
Because of the evaporation, gypsum was left behind. The wind blew the gypsum to form sand dunes in the White Sand Dune Figure Acknowledgements: The author appreciates the following people who have made this report possible. Staff members of the Lodge provided the author information and places to observe geological features.
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Steven Henry of Cloudcroft, a geologist, took me out to the field and showed me sedimentary rocks and faults. Ed Woten also of Cloudcroft showed me his fossil collection and took me to a place where fossils can be found. People at Cloudcroft Forest Service Office were very courteous and helpful in giving the author information on mines, trails, and geology in the Sacramento Mountains.
References cited: Allen, B. Chapin, C. Seager, W. Readers may like to see pictures of the fossils.