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Fort Rock Basin / Christmas Valley

Paleolake Fort Rock
LocationOregon
TypeEndorheic pluvial lake
Max. depth75 metres (246 ft)

Paleolake Fort Rock

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The Fort Rock Basin is an endorheic basin in central Oregon. Increased moisture in this semiarid environment during the Pleistocene through increased cloud cover and cooler temperatures resulted in higher lake levels. At its maximum, the lake filled the basin to a depth of 75m (245ft) , with a surface area of over 2,300km2 (900mi2). While this is larger than any modern lakes in Oregon, Paleolake Fort Rock was smaller than any of the other paleolakes to the south.[1]

There are four major shorelines of Fort Rock Basin from the paleolake. These shorelines are identified through recording wave-cut and depositional terraces, lagoons, and convex sedimentary deposits such as bars, spits, and beach ridges. The floor of the Fort Rock Basin is relatively flat at around 1,315m (4,315ft) throughout much of the basin, so the depths of the lake at each level were fairly consistent.

The highest shoreline at 1,384m (4,540ft) is best seen at Fandango Canyon, but traces of beach sediments and wave-washed scarps have also been identified at Cougar Mountain and the southern end of the Connley Hills. The lake had an average depth of 70 meters (230 feet), with a maximum depth of 76 meters (250 feet) at the eastern edge of the basin. The Connley Hills and Buchgrass Butte formed two major islands.

The next shoreline at 1,364-67m (4,475-85ft) is seen at only a few places in the Fort Rock Basin, such as Fandango Canyon and Cougar Mountain. This level formed the caves at the top of the southern toe of the Connley Hills. The lake was 52 meters (170 feet) deep at this level and covered an area of 1,945km2 (1208mi2). The only islands exposed were the Connely Hills, Buchgrass Butte, and the Fort Rock tuff ring.

The 1,353-56m (4,440-50ft) shoreline is the most strongly developed, as it carved the notches in Fort Rock and the caves in the Connley Hills and Cougar Mountain. The lake was, on average, 38 meters (125 feet) deep and covered 1736km2 (1078mi2).

The lowest shoreline at 1,332m (4,370ft) is seen as wave-washed cliffs at Flatiron Ridge and beach ridges and bars all over the basin. The lake was relatively shallow at about 17 meters (55 feet) deep and 1323km2 (511mi2). This level was almost 1000km2 smaller than the lake at its high stand.[1]

Archaeology in Fort Rock Basin

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Fort Rock Cave

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Prior to the excavation of the Paisley Caves, Fort Rock Cave was the earliest evidence of human occupation in the Oregon. The cave was initially excavated by Luther Cressman in 1938 and during this summer his team discovered numerous well preserved sagebrush-bark sandals.[2] This collection has been named the oldest-dated footwear, as the oldest sandal dates to around 10,000 years old.[3] The cave is located approximately 1.5 miles (2.4 km) west of Fort Rock near Fort Rock State Natural Area in Lake County. Fort Rock Cave was declared a National Historic Landmark in 1961, and added to the National Register of Historic Places in 1966.[4]

Connley Caves

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The Connley Caves are six wave-cut notches in the Connley Hills that have been intermittently occupied from at least 11,200 BP to 3,140 BP. Volcanic ash from the Mazama eruption created a notable layer dating to 6,850 BP that was found in all the caves. The pre-Mazama archaeological deposits were rich in the bones of marshland animals, including birds such as ducks, sage-grouse, and grebes, small mammals like rabbits, gophers, and ground squirrels, and large animals such as pronghorn antelope, elk, and bison. These animals provide evidence for the previous wetland environment at the Connley Caves. Pine charcoal below the Mazama layer is an additional environmental indicator, as the tree only grows at cooler, wetter elevations.[5] Artifacts from 11,000 BP to 7,000 BP show that the site was a popular camping spot. The assemblage consists of obsidian and fine-grain-basalt projectile points, knives, scrapers, drills, milling stones, cordage, and a variety of other items.[5] Research is ongoing at the Connley Caves with the University of Oregon Archaeological Field School. [6]

Carlon and Boulder Village

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Carlon and Boulder Village are two boulder house sites in the Fort Rock Basin. Carlon Village consists of a number of stone house rings that are visible on the surface. Three test pits near the houses encountered three floors, which contained fish, rodent, rabbit, and large mammal bone were dated to 2040, 1890, and 1780 BP. [5]

Boulder Village is the largest of the stone house sites, with 122 stone rings visible on the surface. Excavations in 17 of the houses recovered 14 radiocarbon dates, ranging from 1510 to 100 BP. The artifact assemblage included projectile points, bifaces, unifaces, obsidian flakes, and ground stone tools. Seeds were recovered from flotation and include specimens of salt sage, chenopods, and juniper.[5]


Summer Lake Edit

There is archaeological evidence of human use of Lake Chewaucan during this time. The oldest known human remains in the Western Hemisphere come from the Paisley Caves, which are 10 miles from Summer Lake currently. Dennis Jenkins of the University of Oregon conducted multiple excavations of the Paisley Caves from 2009 to 2011 and recovered hundreds of coprolites, or desiccated feces. Multiple coprolites were found to contain human DNA, and using radio carbon dating, one was dated to 14,500 years ago. This fecal matter is the oldest known human remains in the Western Hemisphere.[7]

Peer Review

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Interesting topic. I suggest that you focus on the connection between the archaeology of the Paisley Caves and the history of human settlement there to the changing climate observed in paleorecords for the area (as available). It would be interesting to note some key archaeological findings in relation to the changing landscape over time. For example, what was the climate of that area when humans are believed to have first moved into the Paisley Caves? What changes took place as the lakes receded? I think the key for this article will be drawing these connections, and the challenge will be in making sure that it is not simply a discussion of Paisley Caves archaeology. Very interesting topic with lots of potential. Dtolson1 (talk) 17:45, 15 May 2017 (UTC)

Suggestions on Fort Rock Basin page

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It looks like there is room for expanding the article on the Fort Rock Basin especially with regard to environmental history and some archeology. But make links to the Summer Lake page and be sure to not repeat information (too much) from the article on that page. Answer.to.the.rock (talk) 14:52, 17 May 2017 (UTC)

  1. ^ a b Freidel DE. 1994. Palaeolake shorelines and lake-level chronology of the Fort Rock basin, Oregon. In Archaeological Researches in the Northern Great Basin: Fort Rock Archaeology since Cressman, Aikens CM, Jenkins DL (eds). Anthropological Papers 50, University of Oregon Department of Anthropology and State Museum of Anthropology: Eugene; 21–40.
  2. ^ "Fort Rock Sandals". pages.uoregon.edu. Retrieved 2017-06-13.
  3. ^ Connolly, Thomas J.; Finley, Judson Byrd; Smith, Geoffrey M.; Jenkins, Dennis L.; Endzweig, Pamela E.; O&#39, Brian L.; Neill; Baxter, Paul W. (2017/05). "RETURN TO FORT ROCK CAVE: ASSESSING THE SITE'S POTENTIAL TO CONTRIBUTE TO ONGOING DEBATES ABOUT HOW AND WHEN HUMANS COLONIZED THE GREAT BASIN". American Antiquity: 1–16. doi:10.1017/aaq.2017.12. ISSN 0002-7316. {{cite journal}}: Check date values in: |date= (help)CS1 maint: numeric names: authors list (link)
  4. ^ "Fort Rock Cave". oregonencyclopedia.org. Retrieved 2017-06-13.
  5. ^ a b c d Aikens and Jenkins.1994. Environment, Climate, Subsistence, and Settlement: 11,000 Years of Change in the Fort Rock Basin, Oregon. In Archaeological Researches in the Northern Great Basin: Fort Rock Archaeology since Cressman, Aikens CM, Jenkins DL (eds). Anthropological Papers 50, University of Oregon Department of Anthropology and State Museum of Anthropology: Eugene; 1-20.
  6. ^ "Archaeology Field School". pages.uoregon.edu. Retrieved 2017-06-13.
  7. ^ Jenkins, Dennis L.; Davis, Loren G.; Stafford, Thomas W.; Campos, Paula F.; Hockett, Bryan; Jones, George T.; Cummings, Linda Scott; Yost, Chad; Connolly, Thomas J. (2012-07-13). "Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves". Science. 337 (6091): 223–228. doi:10.1126/science.1218443. ISSN 0036-8075. PMID 22798611.