Flat Uplift

Llano Uplift tsohuwar tsohuwar ƙasa ce, ƙananan ƙuƙwalwar ƙasa wanda ke da nisan kilomita 90 (kilomita 140) a diamita  galibi yana cikin Yankunan Blanco, Mason, San Saba, Gillespie, da Blanco, Texas. Ya ƙunshi tsibirin tsibirin Precambrian igneous da metamorphic duwatsu kewaye da outcrops na Paleozoic da Cretaceous sedimentary strata. A mafi faɗin su, duwatsun Precambrian da aka fallasa sun kai kimanin kilomita 65 (kilomita 105) zuwa yamma daga kwarin Kogin Colorado  a ƙarƙashin wani kwandon da ke da faɗi, mai laushi wanda Kogin Llano ya zubar. Dutsen Precambrian ne ke ƙarƙashin kwandon da aka rage kuma yana da iyaka da tsaunuka masu tsawo. Wadannan tuddai sune gefen da aka rarraba na Edwards Plateau, wanda ya kunshi shimfidar Cretaceous sedimentary strata. A cikin wannan kwandon da kuma gefen shi akwai tubalan da suka lalace da ragowar lalacewar Paleozoic wanda ya samar da manyan tuddai.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.

Llano Uplift sananne ne ga manyan gine-Ginin dutse, irin su Enchanted Rock . Yankin ya haɗa da manyan wuraren dutse da yawa kamar Dutsen Granite wanda ke hakar dutse mai ruwan hoda. Bugu da ƙari, yankin ya ƙunshi kawai sanannun ajiyar llanite.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

A cikin 1992, Ma'aikatar Lafiya ta Texas ta gano yankin a matsayin ɗaya daga cikin yankuna huɗu waɗanda ke da babban yuwuwar kasancewar matakan haɗari na iskar radon. Ilimin ƙasa

Ana iya ɗaukar Llano Uplift a matsayin haɓaka ta hanyar ko dai tsarinsa a kan taswirar ƙasa ko tsarin saman duwatsun Precambrian. Ya cancanci a matsayin mai ɗagawa saboda ya ƙunshi babban ginshiki na Precambrian wanda aka fallasa ta hanyar farfajiyarsa da ke kwance a sama da farfajiyar da ke kewaye da Precambarian. Koyaya, Llano Uplift bazai taɓa ɗagawa a matsayin wani abu na musamman ba kuma a lokaci guda a matsayin babban ginshiki. Maimakon haka, yankunan da ke kewaye da shi ne suka ragu a kusa da shi da kuma duwatsun Precambrian da ke ƙarƙashinsa an ɗaukaka su ta hanyar kafawa da hulɗa na Tsarin ƙasa da yawa a lokuta da yawa a lokacin Carboniferous da Cretaceous.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

 Duwatsu na Precambrian 
Precambrian rocks directly underlie the surface of the central and topographically lowest part of the Llano Uplift within a low-relief basin drained of the Llano River and eastward to the valley of the Colorado River. These rocks consist of about  of Middle Proterozoic crystalline basement exposed in an 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.

Duwatsun Precambrian sun kunshi duwatsu masu yawa, metasedimentary, Metavolcanic da metaplutonic waɗanda ke cikin shekaru daga 1.37 zuwa 1.23 Ga. Wadannan duwatsun metamorphic sun shiga cikin 1.13 zuwa 1.07 Ga, syntectonic zuwa post-tectonic granites. 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 Wadannan duwatsu za a iya raba su zuwa bangarori uku masu iyaka da ake kira yankuna. Ana kiransu yankunan Valley Spring, Packsaddle, da Coal Creek. Kowane ɗayan waɗannan yankuna suna ƙunshe da nau'ikan dutse da shekaru daban-daban kuma an fashewa su, an shiga su, ko kuma an ajiye su a wurare uku daban-daban sannan daga baya aka haɗa su a lokacin Grenville Orogeny. Yankin bazara na kwarin ya ƙunshi gneiss wanda ya ƙunshi Quartz da micro-line feldspar tare da ƙananan Biotite da hornblende. Wataƙila, wannan gneiss ya ƙunshi manyan duwatsu masu tasowa, dutsen wuta, da duwatsu masu haɗari waɗanda suka haɗa da kwararar rhyolite da yaduwar ash; intrusions na igneous; da arkose da aka haɗa da ƙaramin dutse, da shale. Shekarar waɗannan duwatsun metamorphic sun kasance daga 1.29 zuwa 1.23 Ga. Yankin Packsaddle ya ƙunshi galibi schists wanda ya ƙunshi hornblende, Biotite, Muscovite, da actinolite; marbles da duwatsun calc-silicate; Quartzites; da quart-feldspar gneiss. Wadannan duwatsu sun kasance asalin dutse mai laushi, shale, da sandstone da aka haɗa da duwatsun dutse na mafic da felsic da sills masu shiga tsakani. Sun kasance daga 1.27 zuwa 1.25 Ga. An sanya sills na granitic wanda ya shiga cikin waɗannan duwatsu daga 1.255 zuwa 1.250 Ga. Yankin Coal Creek ya ƙunshi kilomita 6.4 (4.0  -tsawon taro na serpentinite (The Coal Creek Serpentinite) wanda ke kewaye da meta-igneous quartz-plagioclase gneiss na Big Branch Gneiss. An sanya kwanan wata na gneiss a 1.33 zuwa 1.30 Ga kuma an canza shi game da 1.29 Ga, a baya fiye da kowane dutse na Llano. Yankin Coal Creek kuma ya ƙunshi diorite plutons, gabbro, amphibolite, mafic schist, ƙananan talc, da ƙananan jikin serpentinite, dukansu sun canza game da 1.26 Ga. Yankin Coel Creek ya bayyana yana wakiltar raguwa na tsibirin tsibirin tare da slice na mantle na teku da ya lalace a ciki.

Bayan 1.2 Ga, sake zagayowar duniya na haɗari na nahiyar da kuma samo asali na dutse, a duniya ana kiranta Grenville orogeny, kuma a cikin gida ana kiranta Llano Orogeny, an tura shi da kuma haɗa waɗannan sassan. Har ila yau, an kara canza su ta hanyar metamorphism a cikin duwatsun da suka fito a yau a cikin Llano Uplift. Manyan plutons na dutse waɗanda ke cikin gida suna samar da babban kashi na fitowar a wasu yankuna kuma wani llanite dike ya shiga su. A lokacin shekaru miliyan 400 tsakanin wurin da aka sanya llanite da farkon tsinkaye na Cambrian, rushewa ta cire kilomita da yawa na dutsen Precambrian.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

 Ƙananan Paleozoic (Cambrian da Ordovician) 
A ciki da kewayen tsawo na Llano akwai ragowar erosional da tubalan da suka lalace na Lower Paleozoic sedimentary strata. A cikin Llano Uplift, waɗannan ragowar da tubalan kuskure galibi suna samar da manyan tuddai. Ƙananan Paleozoic sun ƙunshi sama da mita 600 (2,000  na sandstones na Cambrian, limestones, da dolomites na Moore Hollow Group da Lower Ordovician limestone da dolomite na Ellenburger Group.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 Ƙungiyar Moore Hollow wacce ta ƙunshi sandstone na Hickory, Cap Mountain limestone, da Lion Mountain sandstone, da Wilberns Formation, wanda ya ƙunshi sandstone, limestone. Kungiyar Ellenburger wani tsari ne mara cikakke na ƙananan Ordovician, waɗanda aka raba, daga tushe zuwa sama, cikin Tanyard, Gorman, da Honeycut. Wadannan tsari suna dauke da dutse da dolomites, waɗanda yawanci ba su da tushe kuma ba su da yawa. Wani lalacewa, pre-Devonian paleosurface tare da ingantaccen paleokarst ya yanke Ellenberger Group ta yadda ya ragu daga kauri na mita 570 (1,870  a kusurwar kudu maso gabashin yankin Llano zuwa mita 250 kawai (820  a arewa maso yammacin kusurwar yankin.

Kungiyar Moore Hollow ta rubuta ci gaban teku daga kudu maso gabas a fadin duwatsun Precambrian da suka lalace a lokacin Tsakiyar zuwa Ƙarshen zamanin Cambrian da kuma binnewa a ƙarƙashin bakin teku da kuma kusa da bakin teku. Tekun Cambrian ya bazu zuwa arewa a fadin yankin da aka rushe wani yanki na duwatsu na Precambrian wanda ke da taimakon gida mai girma kamar mita 240 (790 . A sakamakon haka, datti da ke kunshe da raguwa da aka samo a cikin gida, sau da yawa iska ta tara a matsayin mai laushi, mai laushi mai laushi wanda ke rufe Precambrian strata a gindin Moore Hollow Group. Bayan saukar da manyan duwatsun Cambrian da dolomites, Ƙungiyar Lower Ordovician Ellenburger (wanda ya ƙunshi Tanyard, Gorman, da Honeycut Formations) sun tara a cikin dandamali na carbonate mai zurfi. A ƙarshen Lower Ordovician, yankin Tsakiyar Texas ya karkata zuwa gabas kuma ya fallasa ga rushewar iska da karstification.

An samo conodonts na Ordovician na Tsakiya (Chirognathus) a cikin ƙananan ƙananan kuma an adana aljihun dutse na Upper Ordovician, Burnam Limestone, a cikin Tsarin rushewa a cikin Burnet County. Conodonts da aka sake yi da Burnam Limestone sun nuna cewa yankin Llano Uplift mai yiwuwa ne a wani bangare kuma a takaice a cikin ruwa a lokacin Tsakiyar da Upper Ordovician kawai don a cire turɓaya a lokacin waɗannan ambaliyar ruwa ta hanyar rushewa daga baya.

 Tsakiyar Paleozoic (Silurian da Devonian) 
A cikin Llano Uplift, burbushin Silurian da Devonian sun faru an kiyaye su a matsayin cikawar mafita da rushewar tsarin da suka bambanta da girman daga manyan sinks na tsari zuwa cikawar 'yan inci ko ƙasa da faɗin. Abubuwan da aka ware na burbushin burbushin Starcke Limestone da aka adana a cikin tsoffin sinkholes da aka haɓaka a cikin Ellenberger Group suna ba da tabbacin shaidar yankin Llano da raguwa ruwa ya mamaye aƙalla sau ɗaya a lokacin Silurian Period. Fossil Devonian limestones na nau'o'i daban-daban waɗanda aka adana a cikin kogon, rushewar ɓacin rai, da sauran fasalulluka na paleokarst da suka bunkasa a cikin Ellenberger Group suma sun nuna cewa yankin Llano ya cika da ruwa a lokacin Devonian. A lokacin bayyanar iska, an cire waɗannan ajiya daga yankin Llano Uplift. Aljihun da ragowar sassan Devonian da aka adana a cikin paleokarst sun haɗa da Tsarin Bear Spring, Pillar Bluff Limestone, Tsarin Stribling, kuma, a wani ɓangare, Tsarin Houy. Breccias da aka samo a gindin aljihun Devonian strata mai yiwuwa suna wakiltar cakuda ragowar da aka haɓaka ta hanyar subaerial, a cikin rushewar dutse mai laushi da dolomites da ragowar lalacewa kuma sake sanyawa ta hanyar ci gaba da bakin teku.

 Late Paleozoic (Carboniferous da Permian) 
Kamar Devonian strata da aka samu a cikin Llano Uplift, farkon Carboniferous (Mississippi) strata, mafi ƙanƙanta baƙar fata na Houy Formation, crinoidal limestone na Chappel Limestone da baƙar fata shale Barnett Formation sun ƙunshi aƙalla 'yan mita na strata da suka adana a cikin tsarin rushewa da sauran palestokar. Kamar yadda yake ga Devonian da Silurian strata da aka samu a cikin Llano uplift, waɗannan strata suna wakiltar gajeren lokaci na ambaliyar yankin ta hanyar teku mai zurfi da kuma ruwa mai zurfi wanda ke canzawa tare da dogon lokaci na bayyanar ƙasa a lokacin da aka cire waɗannan ruwa na ruwa kusan gaba ɗaya ta hanyar rushewa.

Late Carboniferous (Lower Pennsylvanian) strata suna da yawa a cikin yankuna uku da ba su da iyaka. Na farko, wani yanki mai banƙyama na Smithwick Shale da Marble Falls Limestone yana faruwa a kusa da Marble Fall, Texas, yankin da ke kudu maso yammacin Burnet County. Na biyu, a kudu maso yammacin Mason County da arewa maso gabashin Kimble County, marigayi Carboniferous Marble Falls Limestone da ke rufe ƙananan ƙananan ƙananan Carboniferal an fallasa shi a cikin rabin dozin, ɓangarorin kuskure a gefen kudu maso yamma na yankin Llano. A ƙarshe, ƙarshen Carboniferous an fallasa su kamar yadda yake a cikin yanki mai siffar triangular wanda Kogin Colorado ya raba shi tare da arewa maso yamma, arewa, da arewa maso gabashin yankin Llano a cikin yankunan McCulloch, San Saba, da Lampasas. A cikin wannan yanki, Marble Falls Limestone, Smithwick Shale, da ƙananan Strawn Group suna da kyau. Yankunan ƙananan Strawn Group an yanke su ta hanyar rashin daidaituwa wanda ya mamaye ƙananan Cretaceous strata.  

Tsarin Carboniferous a ciki da kusa da Llano Uplift ya rubuta yadda aka bayyana raguwa da cikawa da ke kusa da Fort Worth Basin ta hanyar ci gaba zuwa yammacin Delta da tsarin kogin masu alaƙa daga tsaunukan Ouachita zuwa gabas. Chappell Limestone da Barnett Shale suna wakiltar ambaliyar ruwa ta farko ta Carboniferous na yankin Llano ta biyo bayan nutsewa da kuma samar da dandalin carbonate wanda Marble Falls Limestone ya tara a matsayin gefen daidai da ruwa mai zurfi Smithwick Shale. Yayin da Fort Worth Basin ya zurfafa kuma ya nutse a cikin martani ga Ouachita Orogeny, an ajiye Smithwick Shale a kan tsoffin shafuka na Marble Falls a cikin yankin Llano Uplift. A cikin zurfin ɓangaren yankin Llano, shale-fill shale da kuma ajiyar fan na karkashin ruwa waɗanda suka samar da ƙananan Strawn Group sun tara. Kamar yadda kwandon ya cika a lokacin ragowar Carboniferous da Permian, ruwan da ke cikin kogi-deltaic da kuma abubuwan da ke tattare da su na ruwa na sama na Strawn, Canyon, da ƙungiyar Cisco sun tara a cikin Fort Worth Basin.  

 Mesozoic 
Dutse na Mesozoic kawai da aka sani a yankin Llano sune na tsarin Cretaceous. A duk lokacin Triassic da Jurassic, yankin Llano ya lalace. Tattara Triassic, jan gadaje na duniya na Dockham Group na iya kaiwa ga gefen yammacin yankin Llano. Koyaya, an rushe su zuwa matsayinsu na yanzu kuma an rushe ƙananan ɓangarorin a lokacin Triassic da Jurassic don amsawa ga karkatawar yanki da haɓaka.

A lokacin da yankunan Llano Uplift suka rufe sannu a hankali da ajiyar sedimentary na Cretaceous, an rage shi ta hanyar rushewa zuwa ƙasa mai sauƙi mai suna Wichita paleoplain .  Abin da aka gudanar da bincike a kan Wichita paleoplain ya kiyasta cewa kusan mita 33 (108  na taimako ya wanzu a kan wannan farfajiyar da aka yanke a cikin ƙananan sassan. A lokacin Cretaceous, an ci gaba da binne wannan farfajiyar ta hanyar tarawa na ruwa da na bakin teku na Trinity Group kuma daga baya ta Walnut, Comanche Peak, da Edwards.Ewing, T.E., 2016. Texas Through Time: Lone Start Geology, Landscapes, and Resources. Texas Bureau of Economic Geology, Austin TX; 431 p. 

 Cenozoic 
Rushewar da ta faru tun lokacin da aka janye teku na Cretaceous ya haifar da juyawa. A sakamakon haka, tsofaffin duwatsu masu tsawo suna faruwa a mafi ƙasƙanci. Inda duwatsun Cretaceous ke gefen tsaunuka na Llano, tsaunuka masu tsawo ko tsaunuka sun zama ruwan dare.

 Yankin Ma'adinai na Tsakiya 
Yankin Llano Uplift kuma ana kiransa yankin Mineral na Tsakiya na Texas saboda faruwar ma'adanai iri-iri da aka samu a ciki da kuma ramukan neman ma'adinai da yawa da aka tono a cikin duwatsun Precambrian da aka fallasa da Lower Paleozoic strata. A cikin shekarun da suka gabata, wasu ƙananan ma'adanai sun samar da yttrium da sauran ma'adinai masu ban sha'awa, Magnetite, feldspar, vermiculite, serpentin, da kuma topaz mai daraja. A takaice dai, an haƙa galena a matsayin ma'adinai na gubar daga dutse mai laushi wanda ya kasance a kan tuddai na dutse kafin a nutsar da shi ta hanyar hauhawar matakin teku a cikin Cambrian. An sami ƙananan nune-Kunnen zinariya, azurfa, jan ƙarfe, tin, bismuth, molybdenum, tungsten, da ma'adanai na uranium kuma an bincika su a cikin ramuka. Kafin a rufe shi a cikin 1980, ma'adinin graphite na Kudu maso Yammacin arewa maso yammacin Burnet, Texas, shine kawai babban mai samar da graphite mai tsabta a Arewacin Amurka na shekaru da yawa. A baya an tono adadi mai yawa na sabulu daga wuraren da ke kudu da Llano, Texas, da ƙasa don amfani da shi azaman mai ɗaukar maganin kwari da mai cikawa a cikin samfuran daban-daban. Babban albarkatun ma'adinai da aka samar a halin yanzu daga yankin Ma'adinai na Tsakiya sun hada da yashi mai fashewa ("Frac yashi"), dutse mai murkushewa, da dutse mai gini. An fitar da dutse daga kusan wurare da yawa kuma samar da dutse mai girma yana ci gaba a yau daga wani dome na dutse mai ruwan hoda na Town Mountain Granite kusa da Marble Falls, Texas.

 Manazarta 

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