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Table Top Jasper/Chert (Grand/Larimer Co. Colorado)
Table Top Jasper/Chert (Grand/Larimer Co. Colorado)
The larger piece to the right:
Photo courtesy of [Chase]
[addition by painshill]:
This material (with spellings of both Table Top and Tabletop) suffers from some potential naming confusions, both with respect to its origin and its type. The Colorado Geological Survey refers to the general area as “Middle Park”, straddling Grand and Larimer Counties in the north-central part of the state, but provides this cautionary note with its map:
“Because nature did not know that humans were going to try and name various topographic features, these features were not created in the most orderly fashion. Thus, human-designed pigeonholes for naming topographic features can get a bit messy. Moreover, various features have been named by more than one person. Local usage can also lead to confusion, and the boundaries of various features are not particularly clear-cut. With those disclaimers, this map is the compiler’s best attempt at showing the names and locations of various significant features in Colorado. Where possible, preference was given to the original designers of the features.”
There is a potential for confusion with the “Table Mountains” to the southeast (North and South Table Mountains in Jefferson County, central Colorado) and also with the “Flat Top Mountains”, west of Grand and Larimer Counties in the area where Routt, Rio Blanco, Garfield and Eagle Counties meet. Hence, there are multiple flat-topped table landforms, plateaus, mesas and buttes in the general region which have local nicknames that are not necessarily aligned with their recognised geological names. There is also a possibility of confusion with Table Top/Tabletop/Table Mountain Chert/Jasper from Pinal Co. Arizona which coincidentally has a similar appearance to the Colorado material. It’s neither a chert nor a jasper, but an uncommon highly altered rock type known as a brecciated jasperoid.
From an archaeological point of view, the Colorado Rocky Mountains area is peppered with diverse cherts and jaspers intermixed with volcanic rocks and lava flows, many of which outcrop in very small patches that are virtually exhausted by prehistoric procurement. These materials have also acquired specific local names that are not necessarily aligned to recognised geological formations.
In “Denver: An Archaeological History”, Sarah Nelson reproduces Kevin Gilmore’s source map (below) for lithics in the Greater Denver region. It places the material in Grand County, along with the more well-known Kremmling chert, and refers to the material as a jasper. (Original source - Gilmore, Kevin P. 1991 Bayou Gulch: Geoarchaeology of a Multicomponent Site In Central Colorado).
Jessica Anderson also places the material in the same locality (together with Kremmling Chert, Barger Gulch Chert and Buffalo Peaks Chert) but refers to it as a chert in her 2012 thesis. (ref: “Archaeological Investigations of the River Bluffs Open Space, Windsor, Colorado: a Case Study in Co-Operation between Artefact Collectors, the Public, and Archaeologists” submitted to Colorado State University to support her MA degree.) She provides this locality map:
As she observes: “The geology of the eastern portion of Middle Park consists of volcanic breccias, arkosic sandstones and conglomerates and mudstones (Mayer and Surovell 2005: 605). The geology of the western half of the park consists of claystones, siltstones and conglomerate rocks from the Miocene Troublesome Formation (Mayer and Surovell 2005: 606). The Troublesome Formation produces lenses of high quality chert which have been utilized by prehistoric people throughout history (Kornfeld et al. 2010; Mayer et al. 2010). Most archaeological work conducted in this area of Middle Park focuses on Paleoindian occupations and use of the vast lithic resources that the Troublesome formation provides (e.g. Kornfeld et al 2001; Mayer and Surovell 2005; Surovell et al 2005). The visual appearance of chert ranges considerably, and shows variation in color within the same source.”
Anderson worked closely with Garry Weinmeister, a long-time local collector of artifacts and was able to use items from his extensive collection to map the sources of the lithics used in different time frames and relate them to population mobility.
She uses Andrefsky’s (2005) definition of chert: “this sedimentary rock is defined as fine-grained, cryptocrystalline, silicate quartz and occurs in nodules and layers sandwiched within geologic parent material” which is way too loose a definition for a geologist. It’s a jasper and it looks to be brecciated. She also says “for the purposes of this analysis, as well as to maintain consistency with existing publications (Andrefsky 2005), chalcedony is included within the chert sample” which, again, rides roughshod over the geological distinctions.
Trawling through Weinmeister’s projectile point collection, she (macroscopically, not microscopically) “matched” the points to the comparative collection of lithics housed at the Center of Mountains and Plains Archaeology at Colorado State University.
For example she matched one of his points to a reference sample labelled “Unidentified Chert, Grand County/Table Mountain Jasper” collected by James Benedict from a hill south of 5GA157, Grand County, Colorado (pictured below). It was described as “Orange, brown and red with clear, thin lines running through the rock.” This interchangeable use of the terminology underlines the manner in which archaeologists struggle to come to terms with the more precise names used by geologists. However, since the material appears to be brecciated (rock fragments cemented together by pressure and heat), it may well have chert fragments intermixed with jasper. She goes on to say: “the source of this chert also originates from the Troublesome Formation, which dominates the chert raw material sources in Middle Park (Shroba 2010). The matching projectile point falls into the Foothills Corner Notch typology, as evidenced by the serrations on the blade of the tool.”
The larger piece to the right:
Photo courtesy of [Chase]
[addition by painshill]:
This material (with spellings of both Table Top and Tabletop) suffers from some potential naming confusions, both with respect to its origin and its type. The Colorado Geological Survey refers to the general area as “Middle Park”, straddling Grand and Larimer Counties in the north-central part of the state, but provides this cautionary note with its map:
“Because nature did not know that humans were going to try and name various topographic features, these features were not created in the most orderly fashion. Thus, human-designed pigeonholes for naming topographic features can get a bit messy. Moreover, various features have been named by more than one person. Local usage can also lead to confusion, and the boundaries of various features are not particularly clear-cut. With those disclaimers, this map is the compiler’s best attempt at showing the names and locations of various significant features in Colorado. Where possible, preference was given to the original designers of the features.”
There is a potential for confusion with the “Table Mountains” to the southeast (North and South Table Mountains in Jefferson County, central Colorado) and also with the “Flat Top Mountains”, west of Grand and Larimer Counties in the area where Routt, Rio Blanco, Garfield and Eagle Counties meet. Hence, there are multiple flat-topped table landforms, plateaus, mesas and buttes in the general region which have local nicknames that are not necessarily aligned with their recognised geological names. There is also a possibility of confusion with Table Top/Tabletop/Table Mountain Chert/Jasper from Pinal Co. Arizona which coincidentally has a similar appearance to the Colorado material. It’s neither a chert nor a jasper, but an uncommon highly altered rock type known as a brecciated jasperoid.
From an archaeological point of view, the Colorado Rocky Mountains area is peppered with diverse cherts and jaspers intermixed with volcanic rocks and lava flows, many of which outcrop in very small patches that are virtually exhausted by prehistoric procurement. These materials have also acquired specific local names that are not necessarily aligned to recognised geological formations.
In “Denver: An Archaeological History”, Sarah Nelson reproduces Kevin Gilmore’s source map (below) for lithics in the Greater Denver region. It places the material in Grand County, along with the more well-known Kremmling chert, and refers to the material as a jasper. (Original source - Gilmore, Kevin P. 1991 Bayou Gulch: Geoarchaeology of a Multicomponent Site In Central Colorado).
Jessica Anderson also places the material in the same locality (together with Kremmling Chert, Barger Gulch Chert and Buffalo Peaks Chert) but refers to it as a chert in her 2012 thesis. (ref: “Archaeological Investigations of the River Bluffs Open Space, Windsor, Colorado: a Case Study in Co-Operation between Artefact Collectors, the Public, and Archaeologists” submitted to Colorado State University to support her MA degree.) She provides this locality map:
As she observes: “The geology of the eastern portion of Middle Park consists of volcanic breccias, arkosic sandstones and conglomerates and mudstones (Mayer and Surovell 2005: 605). The geology of the western half of the park consists of claystones, siltstones and conglomerate rocks from the Miocene Troublesome Formation (Mayer and Surovell 2005: 606). The Troublesome Formation produces lenses of high quality chert which have been utilized by prehistoric people throughout history (Kornfeld et al. 2010; Mayer et al. 2010). Most archaeological work conducted in this area of Middle Park focuses on Paleoindian occupations and use of the vast lithic resources that the Troublesome formation provides (e.g. Kornfeld et al 2001; Mayer and Surovell 2005; Surovell et al 2005). The visual appearance of chert ranges considerably, and shows variation in color within the same source.”
Anderson worked closely with Garry Weinmeister, a long-time local collector of artifacts and was able to use items from his extensive collection to map the sources of the lithics used in different time frames and relate them to population mobility.
She uses Andrefsky’s (2005) definition of chert: “this sedimentary rock is defined as fine-grained, cryptocrystalline, silicate quartz and occurs in nodules and layers sandwiched within geologic parent material” which is way too loose a definition for a geologist. It’s a jasper and it looks to be brecciated. She also says “for the purposes of this analysis, as well as to maintain consistency with existing publications (Andrefsky 2005), chalcedony is included within the chert sample” which, again, rides roughshod over the geological distinctions.
Trawling through Weinmeister’s projectile point collection, she (macroscopically, not microscopically) “matched” the points to the comparative collection of lithics housed at the Center of Mountains and Plains Archaeology at Colorado State University.
For example she matched one of his points to a reference sample labelled “Unidentified Chert, Grand County/Table Mountain Jasper” collected by James Benedict from a hill south of 5GA157, Grand County, Colorado (pictured below). It was described as “Orange, brown and red with clear, thin lines running through the rock.” This interchangeable use of the terminology underlines the manner in which archaeologists struggle to come to terms with the more precise names used by geologists. However, since the material appears to be brecciated (rock fragments cemented together by pressure and heat), it may well have chert fragments intermixed with jasper. She goes on to say: “the source of this chert also originates from the Troublesome Formation, which dominates the chert raw material sources in Middle Park (Shroba 2010). The matching projectile point falls into the Foothills Corner Notch typology, as evidenced by the serrations on the blade of the tool.”
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