Editing Llano Uplift

{{Short description|Geologic dome in Texas, United States}}
{{Infobox mountain
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| country = [[United States]]
| state = [[Texas]]
| region = [[Texas Hill Country]]
| district_type = County
| district = [[Llano County, Texas|Llano County]]
| settlement_type = Municipality
| settlement = [[Llano, Texas]]
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| range_coordinates = {{coord|30|10|27|N|99|03|55|W|type:mountain_scale:300000|format=dms|display=inline,title}}
| range_coordinates_ref=
| highest = 
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| length_mi = | length_orientation = 
| width_mi = | width_orientation = 
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<!-- *** Features *** -->
| geology = Precambrian and Paleozoic [[Inliers and outliers (geology)|inlier]] surrounded by Cretaceous uplands.
| orogeny = Grenville orogeny
| period = Mesoproterozoic
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| map = USA Texas
| map_relief = yes
| map_size = 220
| map_caption = location of Llano Uplift in [[Texas]]
}}

The '''Llano Uplift''' is a geologically ancient, low [[Dome (geology)|geologic dome]] that is about {{convert|90|mi|km|sp=us}} in diameter and located mostly in [[Llano County, Texas|Llano]], [[Mason County, Texas|Mason]], [[San Saba County, Texas|San Saba]], [[Gillespie County, Texas|Gillespie]], and [[Blanco County, Texas|Blanco counties]], Texas. It consists of an [[Inliers and outliers (geology)|island-like exposure]] of [[Precambrian]] [[igneous]] and [[metamorphic]] rocks surrounded by outcrops of [[Paleozoic]] and [[Cretaceous]] [[sedimentary]] [[strata]]. At their widest, the exposed Precambrian rocks extend about {{convert|65|mi|km|sp=us}} westward from the valley of the [[Colorado River (Texas)|Colorado River]] and beneath a broad, gentle topographic basin drained by the [[Llano River]].  The subdued topographic basin is underlain by Precambrian rocks and bordered by a discontinuous rim of flat-topped hills. These hills are the dissected edge of the [[Edwards Plateau]], which consist of overlying Cretaceous sedimentary strata. Within this basin and along its margin are [[Graben|down-faulted blocks]] and erosional remnants of Paleozoic strata which form prominent hills.<ref name="BarnesOthers1962a">Barnes, V.E., Bell, W.C., Clabaugh, S.E., Cloud, P.E., Jr., Young, K., and McGehee, R.V., 1962. ''Field Excursion No. 1, November 10–11, 1962: Geology of Llano Region and Austin Area,'' in Rainwater, E.H. and Zingula, R.P., eds., Pp 58-61. ''Geology of the Gulf Coast and Central Texas, and Guidebook of Excursions.'' Houston Geological Society, Houston, Texas. 391 pp.</ref><ref name="BarnesOthers1972a"/><ref name="ClabaughOthers1972a">Clabaugh, S.E., and McGehee, R.V. 1972, ''Precambrian rocks of Llano region,'' in Barnes, V.E., Bell, W.C., Clabaugh, S.E., Cloud, P.E., Jr., McGehee, R.V., Rodda, P.U., and Young, K., eds., Pp. 9-23. ''Geology of the Llano region and Austin area.'' Texas Bureau of Economic Geology Guidebook 13, University of Texas, Austin, Texas. 77 pp.</ref>

The Llano Uplift is well known for its large, [[granite dome]]s, such as [[Enchanted Rock]]. The area includes several major rock quarries like [[Granite Mountain (Texas)|Granite Mountain]] that mine the distinctive pink granite. Further, the area contains the only known deposits of [[llanite]].<ref name="PetrossianOthers2016a"/>

In 1992, the Texas Department of Health identified the area as one of four regions with high potential for the presence of hazardous levels of radon gas.{{Citation needed|date=May 2024}}

== Geology ==
[[File:Llano Uplift geologic map v1.jpg|thumb|Llano Uplift - geologic map]]
The Llano Uplift can be considered an uplift by either its pattern on a [[Geological map|geological]] or [[Structural geology|structural map]] of the top of the Precambrian rocks. It qualifies as an uplift because it consists of an extensive Precambrian [[basement high]] that is exposed by virtue of its surface lying significantly above in elevation the surface of surrounding Precambrian [[Basement (geology)|basement]]. However, the Llano Uplift may not have been ever uplifted as a distinct entity and at a single time as a basement high. Rather, it formed by the areas surrounding it having subsided around it and the Precambrian rocks underlying it having been elevated by the formation and interaction of multiple [[Structural geology|geologic structures]] at multiple times during the [[Carboniferous]] and Cretaceous periods.<ref name="Ewing2016a">Ewing, T.E., 2016. ''Texas Through Time: Lone Start Geology, Landscapes, and Resources''. Texas Bureau of Economic Geology, Austin TX; 431 p. {{ISBN|978-1-970007-09-1}}</ref>

=== Precambrian rocks ===
Precambrian rocks directly underlie the surface of the central and topographically lowest part of the Llano Uplift within a low-[[Topographic relief|relief]] [[Drainage basin|basin]] drained of the [[Llano River]] and eastward to the valley of the [[Colorado River (Texas)|Colorado River]]. These rocks consist of about {{convert|900,000|km2|sqmi|abbr=on}} of Middle [[Proterozoic]] [[crystalline basement]] exposed in an [[Window (geology)|erosional window]] eroded through overlying [[Phanerozoic]] [[sedimentary]] [[strata]]. The Precambrian basement is cut by numerous normal and oblique-slip faults, the result of the [[Ouachita Orogeny]], that juxtapose [[Paleozoic]] strata with the Precambrian rocks.<ref name="BarnesOthers1972a">Barnes, V.E., Bell, W.C., Clabaugh, S.E., Cloud, Jr., P.E., McGehee, R.V., Rodda, P.U., and Young, K., 1972, ''Geology of the Llano region and Austin area, field excursion '' The University of Texas at Austin, Bureau of Economic Geology, Guidebook no. 13, 77 p.</ref><ref name="Mosher1998a">Mosher, S., 1998. ''Tectonic evolution of the southern Laurentian Grenville orogenic belt.'' ''Geological Society of America Bulletin'', 110(11), pp. 1357-1375.</ref><ref name="MosherOthers2008a">Mosher, S., Helper, M., and Levine, J., 2008, ''The Texas Grenville Orogen, Llano Uplift, Texas, Field trip guide to the Precambrian geology of the llano uplift.'' Trip 405 for the Geological Society of America (GSA) Annual Meeting, Houston, Texas, GSA Structural Geology and Tectonics Division, Boulder, Colorado.</ref>

The Precambrian rocks consist of multiply deformed, [[Metasedimentary rock|metasedimentary]], [[Metavolcanic rock|metavolcanic]] and metaplutonic rocks that range in age from 1.37 to 1.23 Ga. These [[metamorphic rock]]s have been [[Intrusive rock|intruded]] by 1.13 to 1.07 Ga, syntectonic to post-tectonic [[granite]]s.<ref name="BarnesOthers1972a"/><ref name="Ewing2016a"/><ref name="Mosher1998a"/> These rocks can be divided into three [[Fault (geology)|fault-bounded]] blocks of strata called ''domains''. They are called the ''Valley Spring'', ''Packsaddle'', and ''Coal Creek'' domains. Each of these domains contain distinctive rock types and ages and were either [[types of volcanic eruptions|erupt]]ed, intruded, or [[Deposition (geology)|deposited]] in three separate areas and later tectonically juxtaposed during the [[Grenville Orogeny]]. The ''Valley spring domain'' consists mainly of [[gneiss]] that is composed of [[quartz]] and [[microcline]] [[feldspar]] with minor [[biotite]] and [[hornblende]]. Likely, this gneiss consists of highly metamorphosed sedimentary, [[volcanic]], and [[intrusive rock]]s that include [[rhyolite]] [[lava|lava flows]] and [[Pyroclastic flow|ash-flow]] [[tuff]]s; igneous intrusions; and [[arkose]] interbedded with minor [[limestone]], and [[shale]]. The age of these metamorphic rocks range from range from 1.29 to 1.23 Ga. The ''Packsaddle domain'' consists mainly of [[schist]]s composed of [[hornblende]], [[biotite]], [[muscovite]], and [[actinolite]]; [[marbles]] and calc-silicate rocks; [[quartzite]]s; and quart-feldspar gneiss. These rocks were likely originally marine limestone, shale, and [[sandstone]] interbedded with [[mafic]] and [[felsic]] volcanic rocks and intrusive [[Sill (geology)|sills]]. They date from 1.27 to 1.25 Ga. Granitic sills that intrude these rocks have been dated from 1.255 to 1.250 Ga. The ''Coal Creek domain'' consists of a {{convert|6.4|km|mi|sp=us}}-long mass of [[serpentinite]] (The [[Coal Creek Serpentinite (Texas geology)|Coal Creek Serpentinite]]) that is surrounded by meta-igneous quartz-[[plagioclase]] gneiss of the [[Big Branch Gneiss]]. The gneiss has been dated at 1.33 to 1.30 Ga and was metamorphosed about 1.29 Ga, earlier than any other Llano metamorphic rocks. Coal Creek domain also contains [[diorite]] [[pluton]]s, [[gabbro]], [[amphibolite]], mafic schist, minor [[talc]], and smaller serpentinite bodies, all of which were metamorphosed about 1.26 Ga. The Coal Creek domain appears to represent fragments of an [[island arc]] with a slice of oceanic [[Mantle (geology)|mantle]] faulted into it.<ref name="BarnesOthers1972a"/><ref name="Ewing2016a"/><ref name="Mosher1998a"/><ref name="MosherOthers2008a"/>

After 1.2 Ga, a global cycle of [[continental collision]] and the resulting [[mountain formation]], globally called the [[Grenville orogeny]], and locally called the Llano Orogeny, tectonically shoved and interleaved together these strata. They were also further altered by [[metamorphism]] into the rocks that [[outcrop]] today in the Llano Uplift. Large granitic plutons that locally form a large percentage of the outcrop in some areas and a llanite dike also intruded them. During the 400-million year interval between the emplacement of llanite and the start of Middle [[Cambrian]] [[Deposition (geology)|sedimentation]], [[erosion]] removed several kilometers of Precambrian rock.<ref name="BarnesOthers1972a"/><ref name="Ewing2016a"/><ref name="Mosher1998a"/>

=== Lower Paleozoic (Cambrian and Ordovician) ===
Within and around the Llano uplift are erosional remnants and down-faulted blocks of Lower Paleozoic sedimentary strata. Within the Llano Uplift, these remnants and fault blocks often form prominent hills. The Lower Paleozoic strata are composed of over {{convert|600|m|ft|sp=us}} of Cambrian sandstones, limestones, and [[Dolomite (rock)|dolomite]]s of the [[Moore Hollow Group]] and Lower Ordovician limestone and dolomite of the [[Ellenburger Group]].<ref name="BarnesOthers1972a"/><ref name="Ewing2016a"/> The Moore Hollow Group which consists of the [[Hickory sandstone]], [[Cap Mountain limestone]], and [[Lion Mountain sandstone]], and the [[Wilberns Formation]], which consists of sandstone, limestone, shale, and an upper mixture of limestone and dolomite.<ref name="BarnesOthers1972a"/><ref name="BarnesOthers1977a">Barnes, V.E., and W.C. Bell, 1977, ''The Moore Hollow Group of Central Texas.'' Report of Investigations 88, 169 p. University of Texas, Austin, Bureau of Economic Geology.</ref> The Ellenburger Group is an incomplete sequence of Lower [[Ordovician]] strata, which are divided, from the base up, into the [[Tanyard Formation|Tanyard]], [[Gorman Formation|Gorman]], and [[Honeycut Formation|Honeycut]] formations. These formations contain limestones and dolomites, which are typically [[glauconite|nonglauconitic]] and sparingly [[fossil]]iferous. An erosional, pre-[[Devonian]] [[paleosurface]] with well-developed paleo[[karst]] truncates the Ellenberger Group such that it thins from a thickness of {{convert|570|m|ft|sp=us}} in the southeastern corner of the Llano region to only {{convert|250|m|ft|sp=us}} in the northwestern corner of the region.<ref name="BarnesOthers1972a"/><ref name="CloudOthers1948a">Cloud, P. E., and Barnes, V. E., 1948, ''The Ellenburger Group of Central Texas.'' Publication 4621, 473 p. University of Texas, Austin, Bureau of Economic Geology.</ref>

The Moore Hollow Group records the advancing of a sea from the southeast across eroded Precambrian rocks during Middle to Late Cambrian times and subsequent burial beneath coastal and nearshore marine [[sediment]]s. The Cambrian sea spread northward across the eroded surface an area of Precambrian rocks that had a local relief as great as {{convert|240|m|ft|sp=us}}. As a result, sediments composed of locally derived [[residuum (geology)|residuum]], often wind-abraded accumulated as a thin, discontinuous [[Cobble (geology)|cobble]] [[Conglomerate (geology)|conglomerate]] overlying Precambrian strata at the base of the Moore Hollow Group. Following the deposition of the uppermost Cambrian limestones and dolomites, the Lower Ordovician Ellenburger Group (composed of the Tanyard, Gorman, and Honeycut Formations) accumulated within shallow-water [[carbonate platform]]s. At the end of the Lower Ordovician, the Central Texas region was tilted eastwards and exposed to subaerial erosion and [[karst]]ification.<ref name="BarnesOthers1977a"/><ref name="CloudOthers1948b">Cloud, P.E. and Barnes, V.E., 1948. ''Paleoecology of the early Ordovician sea in central Texas.'' In ''National Research Council, Division Geology and Geography, Report of The Committee on a Treatise on marine ecology and paleo-ecology.'' 8, pp. 29-83.</ref><ref name="CloudOthers1957b">Cloud, P.E. and Barnes, V.E., 1957. In H.S. Ladd, ed. ''Treatise on marine ecology and paleoecology.'' ''Geological Society of America Memoir'' 67:163– 214.</ref>

Possible reworked Middle Ordovician [[conodont]]s (Chirognathus) have been found in younger strata and a pocket of Upper Ordovician limestone, the Burnam Limestone, is preserved in a [[sinkhole|collapse structure]] in Burnet County. The [[Reworked fossil|reworked conodonts]] and the Burnam Limestone indicate that the region of the Llano Uplift was likely either partially and briefly submerged during the Middle and Upper Ordovician only to have the sediments deposited during these inundations removed by later erosion.<ref name="BarnesOther1953a">Barnes, V.E., Cloud Jr, P.E. and Duncan, H., 1953. ''Upper Ordovician of central Texas.'' ''American Association of Petroleum Geologists Bulletin'', 37(5), pp. 1030-1043.</ref><ref name="Seddon1970a">Seddon, G., 1970. ''Pre-Chappel conodonts of the Llano region, Texas.'' Texas Bureau of Economic Geology Report of Investigation no. 68, University of Texas, Austin, Texas. 130 pp.</ref>

=== Middle Paleozoic (Silurian and Devonian) ===
Within the Llano Uplift, fossiliferous Silurian and Devonian strata occur preserved as the fills of solution and collapse structures that vary in size from large structural sinks to crack fillings a few inches or less in width. Isolated deposits of fossiliferous Starcke Limestone preserved in ancient sinkholes developed in the Ellenberger Group provide definite evidence of the Llano region having been inundated by marine waters at least once during the [[Silurian]] Period. Fossiliferous Devonian limestones of various types that are preserved in cave fills, collapse depressions, and other paleokarst features develop in the Ellenberger Group also demonstrate that the Llano region was also episodically inundated by marine waters during the Devonian period. During periods of subaerial exposure, these deposits were largely stripped from the region of the Llano Uplift. The pockets and remnants of Devonian strata preserved in paleokarst included the Bear Spring Formation, Pillar Bluff Limestone, Stribling Formation, and, in part, the Houy Formation. Breccias found at the base of the base of the pockets of Devonian strata likely represent a mixture of [[residuum (geology)|residuum]] developed by the subaerial, in situ dissolution of underlying limestones and dolomites and residuum eroded and redeposited by an advancing marine shoreline.<ref name="BarnesOther1953a"/><ref name="Seddon1970a"/><ref name="BarnesOther1947a">Barnes, V.E., Cloud, P.E. and Warren, L.E., 1947. ''Devonian rocks of central Texas.'' ''Geological Society of America Bulletin'', 58(2), pp. 125-140.</ref><ref name="CloudOthers1957c">Cloud, P.E., Barnes, V.E. and Hass, W.H., 1957. ''Devonian-Mississippian transition in central Texas.'' ''Geological Society of America Bulletin'', 68(7), pp. 807-816.</ref>

=== Late Paleozoic (Carboniferous and Permian) ===
Like the Devonian strata found in the Llano Uplift, early [[Carboniferous]] ([[Mississippian (geology)|Mississippian]]) strata, the youngest black shale of the Houy Formation, the [[crinoid]]al limestone of Chappel Limestone and the black shale Barnett Formation consist of at most a few meters of strata preserved within collapse structures and other paleokarst. As in case of the Devonian and Silurian strata found within the Llano uplift, these strata represent brief periods of inundation of the region by shallow [[Inland sea (geology)|epicontinental seas]] and marine sedimentation alternating with long periods of terrestrial exposure during which these marine sediments were almost completely removed by erosion.<ref name="Seddon1970a"/><ref name="BarnesOther1947a"/><ref name="CloudOthers1957c"/><ref name="GraysonOthers1987a">Grayson, R.C., Merrill, G.K. and Miller, J.F., 1987. ''Early and Late Paleozoic conodont faunas of the Llano Uplift Region, Central Texas-biostratigraphy, systemic boundary relationships, and stratigraphic importance. 21st Annual Meeting South - Central Section The Geological Society of America, Waco, Tx. March 28, 29, 1987.'' Geological Society of America, Boulder, Colorado. 154 p.</ref><ref name="LouksOthers2007a">Loucks, R.G. and Ruppel, S.C., 2007 ''Mississippian Barnet Shale: Lithofacies and depositional setting of a deep-water shale-gas succession in the Ft. Worth Basin, Texas.'' ''American Association of Petroleum Geologists Bulletin'', 91(4), pp.5 76-601.</ref>

Late Carboniferous ( Lower Pennsylvanian ) strata are in large part exposed in three non-contiguous areas. First, an isolated areal exposure of Smithwick Shale and underling Marble Falls Limestone occurs near [[Marble Falls, Texas]], area in southwestern Burnet County.  Second, in southwestern Mason County and northeastern Kimble County, late Carboniferous Marble Falls Limestone overlying relatively thin early Carboniferous strata is exposed within a half dozen, isolated fault blocks on the southwestern periphery of the Llano region. Finally, late Carboniferous are exposed as within a triangular shaped region that is bisected by the Colorado River along the northwest, north, and northeast periphery of the Llano region in McCulloch, San Saba, and Lampasas counties. In this area, Marble Falls Limestone, Smithwick Shale, and lower Strawn Group are well exposed. The strata of the lower Strawn Group are truncated by an erosional unconformity that is overlain by much younger Cretaceous strata.<ref name="BarnesOthers1972a"/><ref name="GraysonOthers1987a"/><ref name="LouksOthers2007a"/>

The succession of Carboniferous strata within and adjacent to the Llano Uplift records the pronounced subsidence and filling of the adjacent [[Fort Worth Basin]] by the westward progradation of [[River delta|delta]] and associated [[fluvial]] systems from the uplifted Ouachita Mountains to the east. The Chappell Limestone and Barnett Shale represent episodic early Carboniferous inundations of the Llano region followed its submergence and formation of a carbonate platform within which the Marble Falls Limestone accumulated as a lateral equivalent to deeper water Smithwick Shale. As the Fort Worth Basin deepened and sank in responses to the Ouachita Orogeny, Smithwick Shale was deposited on former sites of Marble Falls sedimentation within the Llano Uplift region. In the deeper part of the Llano region, basin-fill shale and [[Abyssal fan|submarine fan deposits]] that form the lower Strawn Group accumulated. As the basin filled during the remainder of the Carboniferous and Permian, fluvial-deltaic sediments and associated shallow marine continental shelf deposits of the upper Strawn, Canyon, and Cisco group accumulated within the Fort Worth Basin.<ref name="GraysonOthers1987a"/><ref name="BrownOthers1987a">Brown, L.F., Cleaves, A.W. and Erxleben, A.W., 1973. ''Pennsylvanian depositional systems in north-central Texas: A guide for interpreting terrigenous clastic facies in a cratonic basin'', Guidebook 14, Bureau of Economic Geology, University of Texas at Austin, 122 pp.</ref><ref name="AlsalemOthers2017a">Alsalem, O.B., Fan, M. and Xie, X., 2017. ''Late Paleozoic Subsidence and Burial History of the Fort Worth Basin.'' ''American Association of Petroleum Geologists Bulletin'', 101(11) pp. 1813–1833.</ref>

=== Mesozoic ===
The only Mesozoic rocks that are known in the Llano region are those of the Cretaceous system. Throughout [[Triassic]] and [[Jurassic]]  periods, the Llano region was eroded. The accumulation of Triassic, terrestrial red beds of the Dockham Group may have reached to the western edge Llano region. However, they were eroded back to its present position and underlying strata eroded during the Triassic and Jurassic in response regional tilting and uplift.<ref name="Ewing2006a">Ewing, T.E., 2006. ''Mississippian Barnett Shale, Fort Worth basin, north-central Texas: Gas-shale play with multi–trillion cubic foot potential: Discussion. American Association of Petroleum Geologists Bulletin'', 90(6), pp. 963-966.</ref>

By the time that the regions of the Llano Uplift was slowly covered by Cretaceous sedimentary deposits, it had been reduced by erosion to a low relief erosion surface termed the Wichita [[paleosurface|paleoplain]].<ref name="Hill1901a">Hill, R.T., 1901. ''Geography and geology of the Black and Grand prairies, Texas, with detailed descriptions of the Cretaceous formations and special reference to artesian waters.'' ''United States Geological Survey Annual Report'', Vol. 21, Part 7, 666 pp.</ref> What little research has been conducted on the Wichita paleoplain estimates that as much as {{convert|33|m|ft|sp=us}} of relief exists on this surface cut into the underlying strata. During the Cretaceous, this surface was progressively buried by the accumulation of fluvial and coastal sediments of the Trinity Group and later by the Walnut, Comanche Peak, and Edwards formations.<ref name="Ewing2016a"/><ref name="Hill1901a"/><ref name="AtchleyOthers2001a">Atchley, S.C., L.M. Zygo, and J. Wallgren, 2001, ''Topographic Irregularities on the Base Zuni Supersequence Boundary and their Initial Cretaceous Sediment Fill, Central Texas.'' ''Gulf Coast Association of Geological Societies Transactions'', 51, p. 1–8.</ref>

=== Cenozoic ===
Erosion that has occurred since the withdrawal of Cretaceous seas has resulted in a topographic inversion. As a result,  the oldest and structurally highest rocks tend to occur at the lowest topographic elevations. Where the Cretaceous rocks rim the Llano uplift, a sharp topographic rise or [[escarpment]] is common.<ref name="Rose2016a">Rose, P.R., 2016. ''Late Cretaceous and Tertiary burial history, central Texas''. ''GCAGS Journal'', 5, pp.141-179.</ref><ref name="Rose2019a">Rose, P.R., 2019. ''Evolution of the Central Texas Landscape and the Edwards Aquifers after Balcones Faulting''. ''GCAGS Journal'', 8, pp.231-267.</ref>

== Central Mineral region ==
The Llano Uplift region is also called the Central Mineral region of Texas because of the occurrence of the great variety of [[mineral]]s found in and the numerous [[ore]] prospecting pits dug into exposed Precambrian rocks and Lower Paleozoic strata. Over the decades, a few small mines have yielded [[yttrium]] and other [[Rare-earth element|rare-earth]] minerals, [[magnetite]], [[feldspar]], [[vermiculite]], [[Serpentine subgroup|serpentine]], and gem quality [[topaz]]. Briefly, [[galena]] as [[lead]] ore was mined from limestone lying unconformably upon granite knobs that were once hills before being submerged by [[Sea level rise|rising relative sea level]] in the Cambrian. Minor showings of [[gold]], [[silver]], [[copper]], [[tin]], [[bismuth]], [[molybdenum]], [[tungsten]], and [[uranium]] minerals have been found and explored in prospecting pits. Before it closed in 1980, the Southwestern Graphite mine northwest of [[Burnet, Texas]], was the only major producer of high-purity [[graphite]] in North America for several decades. In the past large quantities of [[soapstone]] were excavated from outcrops south of [[Llano, Texas]], and ground for use as insecticide carrier and inert filler in various products. The principal mineral resources currently produced from Central Mineral region consist of [[Hydraulic fracturing proppants|fracturing sand (“Frac sand”)]], [[crushed stone]], and building stone. Granite has been quarried from almost innumerable localities and the active production of [[dimension stone]] continues today from a dome of coarse pink Town Mountain Granite near [[Marble Falls, Texas]].<ref name="PetrossianOthers2016a">Petrossian, R., Michael Jacobs, P.G., Meinshausen, M., Guide, F., Mine, V.S. and Maymi, N., 2016. ''Economic Geology Resources of the Llano Uplift Region and the Historical Impacts to the Region’s Growth. Guidebook to the Texas Section- American Institute of Professional Geologists Spring Field Trip, Llano Uplift Region, Central Texas: May 14–15, 2016.'' American Institute of Professional Geologists, Houston, Texas. 71 pp.</ref><ref name="RainwatersOthers1962a">Rainwater, E.H. and Zingula, R.P., 1962. ''Geologic History of Central Texas: Precambrian Rocks of Llano Region.'' in Rainwater, E.H. and Zingula, R.P.,  eds., pp. 62-106,1962. ''Geology of the Gulf Coast and Central Texas and Guidebook of Excursions.'' Houston Geological Society, Houston, Texas. 391 pp.</ref>

<gallery mode=packed caption="Llano uplift context and features">
File:LLanno Uplift shaded relief wide.jpg|Llano area in relief context
File:Enchanted Rock near Fredericksburg.jpg|''Enchanted Rock near Fredericksburg'', painted by [[Hermann Lungkwitz]] in 1864, oil.
File:enchanted_rock_2006.jpg|Enchanted Rock
File:llanite.jpg|Llanite rock
</gallery>

== See also ==
* [[Geology of Texas]]

== Notes ==
{{reflist}}

{{Greater Austin}}
{{Texas}}
{{Mountains of Texas}}

[[Category:Geologic provinces of Texas]]
[[Category:Geologic domes]]
[[Category:Rock formations of Texas]]
[[Category:Landforms of Llano County, Texas]]