Clayton Dinosaur Trackway EarthCache

An easy half-mile walk will bring you to Clayton Lake's spillway and an internationally significant dinosaur trackway, containing more than 500 footprints dating back more than 100 million years. The best times to view the tracks are in the morning and late afternoon.

To log this EarthCache:

NOTE: If you don't know how an EarthCache is different and why there is no container here in this State Park, read this. Please do not leave the boardwalk to get a picture of yourself with the dinosaur tracks. Instead, take a picture of yourself with your GPS in front of the Dinosaur Pavilion or at the bottom of the boardwalk and post it in your log. Then send me the answers to the following questions whose answers can be found on the interpretive signs (if you get your information elsewhere I'll know):

1. At least how many different kinds of dinosaurs walked on these mudflats?
2. How many were bipedal versus quadrupeds?
3. What was the specific name of the flying dinosaur originally thought to have made tracks here?
4. BONUS: Take time to visit the Visitors Center if open. If you do, dig up some fossils and tell me total available to be found.

History of the Park

In 1954, the New Mexico State Game Commission obtained the land to construct Clayton Lake, with the intent of establishing habitat for migratory waterfowl. Construction of a dam across Seneca (or Cinegilla) creek began in 1954, and was completed approximately two years later. Until 1965, the Game Commission and Union County jointly maintained the lake. On August 10, 1965, the New Mexico State Park and Recreation Commission signed an agreement with the Game and Fish Commission, creating Clayton Lake State Park (CLSP). The State Park and Recreation Commission held a formal Dedication Ceremony on June 28, 1968. In 1982 a flood down Seneca Creek caused the lake to overflow and the excess water flowed over the spillway. When the flood was over and things dried up it was discovered that a layer of silt was washed away and uncovered a bonanza of dinosaur tracks, preserved in the Early Cretaceous sandstones of the upper Dakota Group, dated at about 100 million years old.

Geology

Clayton Lake State Park offers a diverse geologic setting. It lies in the Raton section of the Great Plains physiographic province, which is characterized by rolling hills, flat plains, and mesas that were intruded by numerous volcanoes forming lone mountain peaks and cones of various heights above the plains. The southern end of the Raton section is formed by the Canadian escarpment, north of the Canadian River. Basalt flows from the volcanoes protected the underlying sedimentary rocks from erosion and formed the tops of the mesas and flat plains.

The uppermost mesa above Clayton Lake is formed by Quaternary basalt flows that probably erupted from Rabbit Ear Mountain. Rabbit Ear Mountain is actually two summits that were once part of a single volcano, now largely eroded, similar in lithology and emplacement to the younger Capulin Mountain now protected as the Capulin National Monument east of Clayton (See Capulin Volcano Earthcache). The basalts were erupted as continuous flows 9 to 100 ft thick composed of olivine, plagioclase, and augite phenocrysts in a microscopic groundmass of augite, plagioclase, olivine, and magnetite. Many vesicles or small cavities or voids in the basalt formed by gas bubbles as the lava cooled. Some vesicles are filled with calcite crystals. These basalts are part of the Raton–Clayton volcanic field and are about 1.8 million years old (Stormer, 1972). As the visitor descends into the park, the contact between the basalt flow and underlying sediments can be observed along the road.

The basalt flows overlie the red to brown caliche sands of the Ogallala Formation of mid-Miocene to early Pliocene (4–12 million yrs ago) age (Frye et al., 1978). The Ogallala Formation is one of the most widespread units in the United States, extending from South Dakota to southern New Mexico and northwestern Texas, forming the Llano Estacado. The Ogallala Formation, the primary reservoir of ground water throughout the region, is responsible for man changing the appearance and character of the Great Plains. The Ogallala is 0–15 ft thick at Clayton Lake and consists of eolian sand and silt and fluvial sandy clay, siltstone, sandstone, and local gravel derived from the Rocky Mountains about 4–12 million yrs ago (Reeves, 1971; Hawley, 1984). Caliche beds are common throughout the unit. Caliche is composed of fractured and permeable deposits of gravel, sand, silt, and clay that is cemented by calcium carbonate (McGrath and Hawley, 1985).

The Ogallala Formation unconformably overlies the Cretaceous Graneros Shale, which forms covered slopes in the park. The Graneros Shale is predominantly gray shale found in local arroyo cuts and was deposited by the Cretaceous marine sea about 97.5– 91 million yrs ago. Local invertebrate microfossils shaped like grains of rice, called Foraminifera, are found in the shale beds and confirm the Late Cretaceous (Cenomanian) age (Lucas et al., 1986).

The Graneros Shale unconformably overlies the Cretaceous Dakota Group. The Dakota Group consists of rocks that formed along the western shore of the Western Interior Seaway, a shallow oceanic strait that in Cretaceous time connected the Gulf of Mexico with the Arctic Ocean. These rocks were laid down in lakes, rivers, and river deltas, as well as the ocean. Dakota Group strata extend from central New Mexico more or less northward through Colorado to southern Wyoming (east of the present-day Rocky Mountains and extending westward into the Front Range of Colorado). From northern Colorado to central New Mexico, the upper layers of the Dakota Group (dating to the Albian-Cenomanian) are rich in dinosaur tracks and trackways. Crocodilian tracks, as well as the first Mesozoic bird tracks ever found, are also present in some outcrops of the Dakota Group. These tracks are given added importance by the fact that no dinosaur bones have been found in this part of the Dakota Group; the tracks are the only evidence that dinosaurs once lived in the region. Dinosaur Ridge (See Earthcache: GCMQGG - Dinosaur Ridge EarthCache) , just west of Denver, Colorado, is one well-known and publicly accessible tracksite in the Dakota Group.

The Romeroville Sandstone, the upper unit of the Dakota Group, consists of a thick quartzose sandstone unit that forms the lowest benches along the lake. It is yellowish orange to brown, fine to coarse grained, poor to well sorted, and bioturbated. Crossbeds and ripple marks are common locally, indicating fluvial deposition. Most of the beds surrounding the lake and above the spillway belong to the Romeroville Sandstone.

The Romeroville Sandstone overlies the Pajarito Shale. The Pajarito Shale, the middle unit of the Dakota Group, is approximately 12 ft thick and consists of interbedded gray silty shale, shaley siltstone, and quartzose sandstone (Lucas et al., 1986). The upper two horizons of dinosaur footprints are in the Pajarito Shale.

The Pajarito Shale overlies the Mesa Rica Sandstone, the basal unit of the Dakota Group. The Mesa Rica Sandstone is approximately 40 ft thick and consists of grayish-orange, medium- to coarse-grained, poorly sorted, quartzose sandstone (Lucas et al., 1986). Local beds contain crossbeds and ripple marks, indicating fluvial deposition. This unit also contains the stratigraphically lowest horizon (oldest) of dinosaur footprints. It overlies a micaceous shale belonging to the Cretaceous Glencairn Shale.

Clayton tracks

The most exciting geological feature at Clayton Lake State Park is the dinosaur footprints found at the dam spillway about 1982. Earlier studies suggested that the host rocks belonged to the Romeroville Sandstone, but more detailed studies by Lucas et al. (1986) and Hunt and Lucas (1996) showed that the host rocks belong to the Pajarito Shale and underlying Mesa Rica Sandstone, both of which are older than the Romeroville. These stratigraphic studies suggest that the footprints are about 91–100 million yrs old. Approximately 500 tracks of at least three species are found at the spillway; most of them pertain to ornithopod dinosaurs and theropods (Hunt and Lucas, 1996). The dinosaurs ranged in size from a baby Iguanodont that was approximately 1 ft long to adults that were 30 ft long. Most of the tracks are of bipedal herbivores or planteaters. The kite-shaped tracks were made by Iguanodonts walking in wet mud.

These tracks present excellent examples of the behavior of the dinosaurs. One set of prints was made by a swimming crocodile (Hunt and Lucas, 1996). Individual dinosaur tracks are along a single line, indicating that the dinosaur walked with his legs beneath him and not out to the side like modern reptiles. At one spot, the tracks suggest that a large planteater slipped in the mud and used his tail to keep his balance.

Primitive ornithopod dinosaurs, the iguanodonts, made most of the tracks at Clayton Lake. These are the three-toed footprints of animals that either walked bipedally, or occasionally leaned forward to walk on all fours. They are easily recognized because of their square heels and lack of claw marks. In contrast, a few footprints at Clayton Lake are those of theropods, meat-eating dinosaurs. They are easily recognized by their pointed heels and sharp, clawed toes.

The Clayton tracks teach us something very important about dinosaur evolution in North America during the Cretaceous. Prior to 100 million years ago, the Sauropod dinosaurs were the dominant dinosaurian plant eaters. Early Cretaceous footprint sites throughout Texas, Oklahoma and Arkansas were trampled by sauropods. But, at Clayton Lake and at other dinosaur tracksites of the same geologic age in northeastern New Mexico, Oklahoma and Colorado, there isn't a single sauropod footprint! Instead, the footprints suggest ornithopods were the most abundant and conspicuous plant eaters.

The most common tracks at Clayton Lake are broad, three-toed tracks. The largest of these tracks is about thirty centimeters in length, from the tip of the middle toe to the rear. Very similar tracks have been found in Brazil and in England. The tracks, which have been placed in the form genus Caririchnium, were made by ornithopod dinosaurs, large herbivores. The best-known ornithopods are the hadrosaurs, but the Clayton Lake tracks are a little too old to have been made by hadrosaurs. In all likelihood, tracks like the one shown here were made by iguanodontid dinosaurs, whose best-known representative is Iguanodon. Iguanodontids were close relatives and probable ancestors of the hadrosaurs.

The larger main track represents a hind foot impression. Iguanodontids had large hind limbs and smaller forelimbs, and are often reconstructed as being bipedal. However, this track, and countless others like it, is associated with a smaller impression, visible to the side of the main track. These are impressions of the forefeet. The ornithopod dinosaurs that left these tracks may have been quadrupedal, walking on all fours. Or they might have been facultative bipeds, able to switch between bipedal and quadrupedal walking.

You can also spot the ornithopod trackway, with its distinctive broad, three-toed hindfoot track shape associated with some rather unusual tracks, looking rather like kites, but clearly showing three toes at the front. These may be the tracks of small theropod dinosaurs, but could also be tracks of small ornithopods; the "kite shape" may result from the metatarsal part of the foot, which was normally off the ground, contacting the ground when these tracks were made. Definite theropod tracks are known from the Clayton Lake spillway. Another part of the spillway has yielded tracks that were originally thought to belong to a pterosaur. However, they are now known to have been made by crocodiles (Bennett, 1993).

The Environment

Today the park is located at the southwestern edge of the Great Plains. The landscape is characterized by rolling prairie, volcanic rock formations and sandstone bluffs. The average park altitude is approximately 5,050 feet. The average annual temperature is 53 degrees Fahrenheit. July temperatures average 74 degrees Fahrenheit, rarely, but occasionally reaching 100 degrees. January temperatures average 33 degrees Fahrenheit, occasionally dipping to below zero degrees Fahrenheit. The average annual rainfall is 14.12 inches; annual snowfall averages 21.3 inches.

In the Early Cretaceous it was very different. This area was the western shore of a vast inland sea. Here are fossilized features that can be used to reconstruct the environment in which the tracks were made. The markings that crisscross the rock surface are dessication cracks. These can be seen forming today on mud that is drying out; the mud cracks, in a polygonal pattern, as it dries. Also visible is a small patch of ripple marks. These marks formed, and form today, when steady, relatively gentle water currents flow over soft sediments. Ripple marks are also found cross-cut with the dessication cracks, showing that the cracks formed later. The picture that emerges from these clues is of a sandy or muddy flat, partly dried out, but still retaining pools and inlets of shallow water. Over this sand flat, sinking a bit in the not-fully-dry muddy sand, herds of dinosaurs once walked.

FURTHER READING

• Baldwin, B., and Muehlberger, W. R., 1959, Geologic studies of Union County, New Mexico: New Mexico Bureau of Mines and Mineral Resources, Bulletin 63, 171 pp.
• Bennett, S. C. 1993. Reinterpretation of problematical tracks at Clayton Lake State Park, New Mexico: Not one pterosaur, but several crocodiles. Ichnos 2:37-42.
• Folsom, F., 1974, An amateur’s bonanza: discovery of early man in North America: The American West, v. 11, no. 6, pp. 34–39.
• Foster, R., 1983, Clayton Lake: New Mexico Geology, v. 5, pp. 81–82.
• Frye, J. C., Leonard, A. B., and Glass, H. D., 1978, Late Cenozoic sediments, molluscan faunas, and clay minerals in northeastern New Mexico: New Mexico Bureau of Mines and Mineral Resources, Circular 160, 32 pp.
• Gillette, D. D. and Thomas, D. A. 1985. "Dinosaur tracks in the Dakota Formation (Aptian-Albian) at Clayton Lake State Park, Union County, New Mexico": New Mexico Geological Society, Guidebook to 36th Field Conference, pp. 283-288.
• Hawley, J. W., 1984, The Ogallala Formation in eastern New Mexico: Texas Tech University, Water Resources Center, Proceedings of the Ogallala Aquifer Symposium II, pp. 157–176.
• Hunt, A. P., and Lucas, S. G., 1996, A reevaluation of the vertebrate Ichnofauna of the Mesa Rica Sandstone and Pajarito Formations (Lower Cretaceous: Late Albian), Clayton Lake State Park, New Mexico (abs.): New Mexico Geology, v. 18, no. 2, p. 57.
• Julyan, R., 1996, The place names of New Mexico: University of New Mexico Press, Albuquerque, 385 pp.
• Lockley, M. G. and Hunt, A. P. 1995. Dinosaur tracks and other fossil footprints of the western United States. New York, Columbia University Press, 338 pp.
• Lucas, S. G. 1993.Dinosaurs of New Mexico. Albuquerque, New Mexico Academy of Science, 130 pp.
• Lucas, S. G., 1990, Type and reference sections of the Romeroville Sandstone (Dakota Group), Cretaceous of northeastern New Mexico; in Bauer, P. W., Lucas, S. G., Mawer, C. K., and McIntosh, W. C. (eds.), Tectonic development of the southern Sangre de Cristo Mountains, New Mexico: New Mexico Geological Society, Guidebook 41, pp. 323–326.
• Lucas, S. G., Hunt, A. P., Kietzke, K. K., and Wolberg, D. L., 1986, Cretaceous stratigraphy and iostratigraphy, Clayton Lake State Park, Union County, New Mexico: New Mexico Geology, v. 8, pp. 60–65.
• McGrath, D. A., and Hawley, J. W., 1985, Calcretes of the Santa Rosa area; in Lucas, S. G., and Zidek, J. (eds.), Santa Rosa–Tucumcari Region : New Mexico Geological Society, Guidebook 36, pp. 4–6.
• Reeves, C. C., Jr., 1971, Relations of caliche to small natural depressions, southern High Plains, Texas and New Mexico: Geological Society of America, Bulletin, v. 82, pp. 1983–1988.
• Scott, G. R., 1986, Geologic and structure contour map of the Springer 30’x 60’ quadrangle, Colfax, Harding, Mora, and Union Counties, New Mexico: U.S. Geological Survey, Map I–1705, 2 sheets, scale 1:100,000.
• Stormer, J. C., Jr., 1972, Ages and nature of volcanic activity on the southern High Plains, New Mexico and Colorado: Geological Society of America, Bulletin, v. 83, pp. 2443–2448.
• Young, J. V., 1984, The State Parks of New Mexico: University of New Mexico Press, Albuquerque, 160 pp.

Clayton Lake State Park

There is a $5.00 day use fee for vehicles. If you walk or bicycle in there is no charge. There are also campsites available so you can stay and enjoy the fishing. For more information concerning the park check out their brochure: Clayton Lake State park Brochure

This EarthCache was placed by following the NM State park Rules and Regulation Title 19 Chapter 5 part 2 section 22 and Geocache Guidelines

Thanks to the Clayton Lake State Park for allowing placement of this EarthCache! More information on the Dinosaur Trackway can be found at the Clayton Lake State Park Visitors Center, 141 Clayton Lake Rd in Clayton, NM.