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CU-Boulder research efforts dates oldest petroglyphs known in North America
Aug 13th
The petroglyphs located at the Winnemucca Lake petroglyph site 35 miles northeast of Reno consist of large, deeply carved grooves and dots forming complex designs on several large limestone boulders that have been known about for decades, said CU-Boulder researcher Larry Benson, who led the new effort. Although there are no people, animals or handprint symbols depicted, the petroglyph designs include a series of vertical, chain-like symbols and a number of smaller pits deeply incised with a type of hard rock scraper.
Benson and his colleagues used several methods to date the petroglyphs, including determining when the water level the Winnemucca Lake subbasin—which back then was a single body of water connecting the now-dry Winnemucca Lake and the existing Pyramid Lake—reached the specific elevation of 3,960 feet.
The elevation was key to the study because it marked the maximum height the ancient lake system could have reached before it began spilling excess water over Emerson Pass to the north. When the lake level was at this height, the petroglyph-peppered boulders were submerged and therefore not accessible for carving, said Benson, an adjunct curator of anthropology at the University of Colorado Museum of Natural History.
A paper on the subject was published this month in the Journal of Archaeological Science. Co-authors on the study included Eugene Hattori of the Nevada State Museum in Carson City, Nev., John Southon of the University of California, Irvine and Benjamin Aleck of the Pyramid Lake Paiute Tribe Museum and Visitor’s Center in Nixon, Nev. The National Research Program of the U.S. Geological Survey funded the study.
According to Benson, a white layer of carbonate made of limestone precipitated from the ancient, overflowing Winnemucca Lake had coated some of the petroglyph carvings near the base of the boulders. Previous work by Benson showed the carbonate coating elsewhere in the basin at that elevation had a radiocarbon date of roughly 11,000 years ago.
Benson sampled the carbonate into which the petroglyphs were incised and the carbonate that coated the petroglyphs at the base of the limestone boulder. The radiocarbon dates on the samples indicated the carbonate layer underlying the petroglyphs dated to roughly 14,800 ago. Those dates, as well as additional geochemical data on a sediment core from the adjacent Pyramid Lake subbasin, indicated the limestone boulders containing the petroglyphs were exposed to air between 14,800 and 13,200 years ago and again between about 11,300 and 10,500 years ago.
“Prior to our study, archaeologists had suggested these petroglyphs were extremely old,” said Benson, also an emeritus USGS scientist. “Whether they turn out to be as old as 14,800 years ago or as recent as 10,500 years ago, they are still the oldest petroglyphs that have been dated in North America.”
While Native American artifacts found in the Lahontan Basin—which encompasses the Winnemucca Lake subbasin—date to the time period of 11,300 to 10,500 years ago, it does not rule out the possibility that the petroglyphs were carved as early as 14,800 years ago, Benson said.
The oldest dates calculated for the Winnemucca Lake petroglyph site correspond with the time frame linked to several pieces of fossilized human excrement found in a cave in Oregon, said Benson, who also is affiliated with CU’s Institute of Arctic and Alpine Research. The caves, known as the Paisley Caves in south central Oregon, held not only fossilized human coprolites that dated to roughly 14,400 years ago, but also bones of horses and camels that went extinct in North America prior to 13,000 years ago.
The younger time interval calculated for the Winnemucca petroglyphs corresponds to dates obtained from a second significant archaeological finding in the region—Spirit Cave Man, who was discovered more than 70 years ago some 60 miles east of Reno and whose hair, bones and clothing were dated to about 10,600 years ago. The remains of the man, who was found partially mummified in a shallow grave in Spirit Cave, Nev., were discovered with a fur robe, a woven marsh plant shroud and moccasins.
Petroglyphs near Long Lake in central Oregon—which were previously thought to be the oldest examples of rock art in North America—share similar features with some of the rock art the Winnemucca site, said Benson. At least one of the petroglyph panels from Long Lake was buried by ash from an eruption of the nearby Mount Mazama volcano roughly 6,700 years ago, proof that it was carved sometime before the eruption.
“We have no idea what they mean,” Benson said of the Winnemucca Lake petroglyphs. “But I think they are absolutely beautiful symbols. Some look like multiple connected sets of diamonds, and some look like trees, or veins in a leaf. There are few petroglyphs in the American Southwest that are as deeply carved as these, and few that have the same sense of size.”
Benson obtained permission to non-invasively examine the petroglyphs from the Pyramid Lake Paiute Tribe, which owns the land. Study co-author John Southton, a faculty member at University of California, Irvine, radiocarbon dated the material for the study.
-CU-
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Boulder Rangers have a quiet week, goats to invade
Aug 9th
The goats are coming; the goats are coming!
Approximately 300 goats will move onto the Stengel l property (Tallgrass West area) sometime this weekend. The goats are part of a long term project established in 2011 looking at ways to reduce chicory, a blue flowered exotic perennial that has invaded our tallgrass communities. Staff is looking at how goats, cattle and prescribed fire when appropriate effect chicory densities and its’ spread. Thanks to Lynn, Ann Lezberg and others for making this happen.The contractor will be on site 24/7 as permitted by the City. Educational signs have been posted at all access points.
Rangers:
Rangers responded to:
• A report of an injured hiker on the Royal Arch trail. The hiker fell and injured her right ankle.Rangers worked with RMR and AMR on this call.
• A report of a lost hiker in the area of the Royal Arch.
Rangers were able to talk the person back down to the trails.
• A report of a fire in the five mile marker of Left Hand Canyon.
Rangers located three juveniles having a campfire and issued summonses for this offense.
Ranger Job Opening
The open OSMP Ranger Naturalist positions have been posted and we will be accepting applicants through 8/20. If you have any qualified seasonal staff, friends or former co-workers interested please direct them here:
https://bouldercolorado.gov/jobs-and-volunteer
Trail
On Aug 1st, members of the Mountain Bike Patrol joined OSMP staff to construct a temporary trail connection between Community Ditch and Coal Seam Trail. This temporary trail will allow visitors to make a loop on those trails, during construction of the Hwy 93 underpass. Once the underpass is complete, this trail will be closed and restored.
Xcel Energy will be starting the line / pole replacement project in the next couple days. Starting from the South, Plainview area, they will work North using Flatirons Vista access and on to Eldorado substation, their contractor will be using Greenbelt Plateau for employee parking with OSMP placards.
Community Outreach
OSMP started leading public Natural Selections programs into the Weiser property last weekend. Dave Sutherland took a large group to see the sandstone cliffs, turtle backs, rare plants and bald eagles that inhabit this special and fragile place. OSMP will continue to offer public guided hikes through August, September and October while the property is open for visitation. The area can only be visited with an OSMP guide, and the hikes are limited to 15 by reservation. At the end of October, a bald eagle nesting closure goes into effect until next August and the location will be closed once more.
Channel 8 covers the OSMP Art Show – https://vimeo.com/71605401
The art show is located in the Boulder Public Library Canyon Gallery (1001 Arapahoe Avenue, Boulder). The show is open to the public and will run from July 20 – August 28 during normal library hours. Drop in and see how Open Space inspires local artists!
CU: Set your internal clock–go camping for, a WEEK?
Aug 5th
Spending just one week exposed only to natural light while camping in the Rocky Mountains was enough to synch the circadian clocks of eight people participating in a University of Colorado Boulder study with the timing of sunrise and sunset.
The study, published online today in the journal Current Biology, found that the synchronization happened in that short period of time for all participants, regardless of whether they were early birds or night owls during their normal lives.
“What’s remarkable is how, when we’re exposed to natural sunlight, our clocks perfectly become in synch in less than a week to the solar day,” said CU-Boulder integrative physiology Professor Kenneth Wright, who led the study.
Electrical lighting, which became widely available in the 1930s, has affected our internal circadian clocks, which tell our bodies when to prepare for sleep and when to prepare for wakefulness. The ability to flip a switch and flood a room with light allows humans to be exposed to light much later into the night than would be possible naturally.
Even when people are exposed to electrical lights during daylight hours, the intensity of indoor lighting is much less than sunlight and the color of electrical light also differs from natural light, which changes shade throughout the day.
To quantify the effects of electrical lighting, a research team led by Wright, who also is the director of CU-Boulder’s Sleep and Chronobiology Laboratory, monitored eight participants for one week as they went about their normal daily lives. The participants wore wrist monitors that recorded the intensity of light they were exposed to, the timing of that light, and their activity, which allowed the researchers to infer when they were sleeping.
At the end of the week, the researchers also recorded the timing of participants’ circadian clocks in the laboratory by measuring the presence of the hormone melatonin. The release of melatonin is one of the ways our bodies signal the onset of our biological nighttime. Melatonin levels decrease again at the start of our biological daytime.
The same metrics were recorded during and after a second week when the eight participants—six men and two women with a mean age of 30—went camping in Colorado’s Eagles Nest Wilderness. During the week, the campers were exposed only to sunlight and the glow of a campfire. Flashlights and personal electronic devices were not allowed.
On average, participants’ biological nighttimes started about two hours later when they were exposed to electrical lights than after a week of camping. During the week when participants went about their normal lives, they also woke up before their biological night had ended.
After the camping trip—when study subjects were exposed to four times the intensity of light compared with their normal lives—participants’ biological nighttimes began near sunset and ended at sunrise. They also woke up just after their biological night had ended. Becoming in synch with sunset and sunrise happened for all individuals even though the measurements from the previous week indicated that some people were prone to staying up late and others to getting up earlier.
“When people are living in the modern world—living in these constructed environments—we have the opportunity to have a lot of differences among individuals,” Wright said. “Some people are morning types and others like to stay up later. What we found is that natural light-dark cycles provide a strong signal that reduces the differences that we see among people—night owls and early birds—dramatically.”
Our genes determine our propensity to become night owls or early birds in the absence of a strong signal to nudge our internal circadian clocks to stay in synch with the solar day, Wright said.
The new study, which demonstrates just how strong of a signal exposure to natural light is, offers some possible solutions for people who are struggling with their sleep patterns. For example, people who naturally drift toward staying up late may also find that it’s more difficult to feel alert in the morning—when melatonin levels may indicate they’re still in their biological nighttimes—at work or in school.
To combat a person’s genetic drift toward later nights, exposure to more sunlight in the morning and midday could help nudge his or her internal clock earlier. Also, dimming electrical lights at night, forgoing late-night TV and cutting out screen time with laptops and other personal electronic devices also may help internal circadian clocks stay more closely attuned with the solar day, Wright said.
Other CU-Boulder co-authors of the study are doctoral students Andrew McHill and Evan Chinoy; former undergraduate students Brian Birks and Brandon Griffin, both of whom are now professional research assistants; and former postdoctoral researcher Thomas Rusterholz.
-CU-
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