Bright Angel Shale

**Bright Angel Shale** yana ɗaya daga cikin tsarin ilimin ƙasa guda biyar waɗanda suka ƙunshi Cambrian Tonto Group . Shi da sauran tsari na Tonto Group a cikin Grand Canyon, Arizona, da sassa na arewacin Arizona, tsakiyar Arizona, kudu maso gabashin California, kudancin Nevada, da kudu maso gabobin Utah. Bright Angel shale ya ƙunshi burbushin halittu na gida, kore da ja-launin, micaceous, fissile shale (mudstone) da siltstone tare da gida, gadaje masu kauri na launin ruwan kasa zuwa launin ruwan kasa da dutse mai laushi. Yana da kauri daga   . Yawanci, takalma masu laushi da sandstones suna haɗuwa a cikin sikelin cm. Har ila yau, suna nuna tsarin da ya dace wanda ya haɗa da halin yanzu, oscillation, da rikice-rikice. Bright Angel Shale kuma a hankali ya sauka zuwa ƙasa a cikin Tapeats Sandstone. Har ila yau, yana da rikitarwa tare da Muav Limestone. Wadannan haruffa suna sa lambobin sadarwa na sama da na ƙasa na Bright Angel Shale sau da yawa da wuya a bayyana. Yawanci, ƙananan shimfidar shimfidar wuri da sandstones sun lalace zuwa gangaren kore da ja-launin da ke tashi daga Tonto Platform har zuwa tsaunuka da aka kafa ta dutsen da ke kan Muav Limestone da dolomites na Dutsen Faransanci Dolostone . 

## Nomenclature
A cikin 1875, G. K. Gilbert  ya gane cewa ɓangarorin da aka fallasa kusa da ƙasan ɓangarorin Grand Canyon suna kama da waɗanda aka sani a wasu wurare a Arizona a matsayin Tonto Group. Dangane da wannan kamanceceniya, ya sanya sassan da suka zama mafi ƙasƙanci na sassan Phanerozoic a cikin Grand Canyon zuwa Tonto Group. Ba tare da sanya nau'ikan yankuna ba, ya kuma raba Tonto Group zuwa kashi uku, daga ƙarami zuwa tsofaffi, dutse mai laushi, *Tonto shale*, da *Tonto sandstone*.

A shekara ta 1914, L F. Noble  ya sake ba da sunan yankunan Gilbert na Tonto Group. Ya sake ba da sunan Tonto sandstone a matsayin *Tapeats Sandstone* da Tonto shale a matsayin *Bright Angel Shale* . Ya ba da suna Bright Angel Shale bayan Bright Angel Canyon saboda a cikin ganuwar wannan canyon, wannan tsari yana da kyau.

Daga baya a cikin 1922,  an sake bayyana dutsen Marbled kuma an sake masa suna a matsayin *Dutsen Muav* na L. F. Noble . Dangane da ma'anar Noble, Muav Limestone ya ƙunshi saman gadaje na dolomite da ƙananan gadaje na dutse. An bayyana ƙananan gadaje na dutse na Noble a matsayin Muav Limestone kuma yanzu an bayyana Dutsen Dolostone na Faransanci a matsayin gadaje na sama na Noble.

E. D. McKee da C. E. Resser  galibi sun riƙe sunan Noble. Koyaya, sun raba Bright Angel Shale zuwa wasu ƙananan ƙungiyoyi, membobin, bisa ga manyan gadaje na dutse da sandstone a ciki. Koyaya, waɗannan membobin sun sami rikice-rikice kuma ba su da taimako wajen fahimtar stratigraphy na Bright Angel Shale kuma galibi ana watsi da su kuma ba a amfani da su sosai a cikin wallafe-wallafen da aka buga.

## Bayyanawa

A cikin Grand Canyon, Bright Angel Shale yawanci bambanci ne, wani lokacin burbushin halittu, cakuda shale, mudstone, siltstone, sandstone mai kyau, da gadaje masu zaman kansu na dutse. Babban lithology a cikin Bright Angel Shale shine greenish shale wanda ya ƙunshi mafi yawa daga illite da kuma bambancin adadin chlorite da kaolinite. Ana ba da launin ruwan kasa mai launin ruwan kasa ga wasu gadaje na sandstone da siltstone ta hanyar babban kashi na hematitic ooids da ƙarfe oxide cements da suke ciki. Gidajen da aka ware na sandstone mai laushi tare da ko dai basal conglomerate ko conglomeratic sandstone kuma suna faruwa a cikin Bright Angel Shale. Yankin dutse na waɗannan gadaje suna dauke da Quartz, ƙananan adadin potassium feldspars, raguwar dutse, da glauconite. Glauconite kuma yana faruwa a ciki kuma yana ba da launi mai launin kore ga yawancin siltstones da sandstones. Zuwa ga tushe, Bright Angel Shale ya zama mai tsanani tare da karuwar mitar gadajen sandstone har sai ya shiga sannu a hankali cikin Tapeats Sandstone.

Dutsen silt da sandstones na Bright Angel Shale suna nuna tsarin sedimentary a duk fadin Grand Canyon. Wadannan tsarin sedimentary sun hada da laminations na kwance, karamin- zuwa babban sikelin planar tabular da trough cross-stratification, da kuma wavy da lenticular beds. Yankin yashi da aka ware da kuma yashi mai yawa yawanci ba su da tsari kuma suna da tsayi kuma suna rufe wani wuri mai tsabta a cikin gida.

A cikin Grand Canyon, Bright Angel Shale gabaɗaya kusan    kauri. A yammacin Grand Canyon, Bright Angel Shale yana da kauri sama da    kuma yana raguwa zuwa gabas a kauri zuwa kusan    a Toroweap a tsakiyar canyon. Yana da kauri    a cikin Bright Angel Canyon. Rikitarwa mai rikitarwa na Bright Angel Shale tare da Muav Limestone mai zurfi shine babban dalilin bambancin a cikin kaurinsa. Kudancin Grand Canyon, yana raguwa a cikin kauri kawai a cikin Juniper Mountains arewacin Prescott, Arizona.  

## Abubuwan da aka samo asali

A cikin Grand Canyon, Bright Angel Shale shine mafi yawan burbushin halittu daga cikin tsari biyar da suka hada da Tonto Group. Ya ƙunshi burbushin jiki iri-iri kuma yana da wadataccen burbushin halittu. Gabaɗaya, idan aka kwatanta da sauran tsarin Cambrian na Tsakiya a yankin, burbushin jikin Bright Angel Shale suna raguwa kuma suna da wuya. Kodayake ba shi da yawa a cikin burbushin jiki, gadoji na mutum na iya zama mai wadata da burbushin jikin mutum. Gidajen mutum a cikin Bright Angel Shale suna da amfani kamar sauran tsarin Cambrian a cikin Great Basin da Rocky Mountain. Bright Angel Shale ya samar da akalla nau'ikan Trilobites 15 da nau'ikan brachiopods guda hudu. Bugu da kari, an sami nau'i daya na hyoliths, nau'i hudu na yiwuwar arthropods na ruwa, da nau'ikan eocrinoids guda biyu a ciki.

Abubuwan burbushin da aka samo a cikin Bright Angel Shale sun ƙunshi waƙoƙi da hanyoyi na arthropod, burrows na tsutsotsi, da kuma tsarin zama. Wasu daga cikin wadannan an gano su a matakin ichnogenus da ichnospecies. Bugu da kari, an samo tsarin wrinkle a cikin Bright Angel Shale a Yankin Sumner Butte. An rarraba su a matsayin tsarin da aka haifar da kwayoyin cuta.

## Yanayin da aka ajiye
Da farko, Bright Angel Shale, galibi akan kasancewar glauconite, an dauke shi da tarawa a cikin zurfin ɓangaren ruwa. Daga baya, ana fassara Bright Angel Shale a matsayin wani nau'i mai zurfi kuma ana fassara membobinta daban-daban don zama ƙananan laifuka da koma baya. Koyaya, an kuma fassara wasu sassansa kwanan nan kamar yadda suka haɗa da ƙuƙwalwar ruwa da saiti na ruwa wanda abubuwan da suka faru na guguwa suka rinjayi. Wannan fassarar ta dogara ne akan nau'in gado na giciye a cikin sandstones da kasancewar gado mai laushi ko lenticular heterolithic, dukansu biyu suna nuna canjin yanayin ruwa. A ƙarshe, rashin acritarchs a cikin shales, ana ɗaukar lithology mai rinjaye na kafa a matsayin shaida ga ƙaramin tasirin ruwa yayin da aka sauke su. Gidajen shale da aka ware a cikin Bright Angel Shale waɗanda ke ƙunshe da adanawa da kuma bambancin fauna na trilobites, brachiopods da sauran burbushin da za su iya wakiltar lokutan da ba su da zurfi a lokacin lokutan da ke da tsawo, matakan teku a yankin Grand Canyon.

## Shekaru
A cikin 1945, E. D. McKee da C. E. Resser  sun yi amfani da tarin burbushin trilobite don tantance shekarun Bright Angel Shale. Sun fassara trilobite Biostratigraphy don nuna cewa ya ƙetare layin lokaci kuma ya zama ƙarami zuwa gabas. A cikin fassararsu, tushe na Bright Angel Shale da ƙananan kashi ɗaya bisa uku na shi shine ƙarshen farkon Cambrian yayin da a gabashin ɓangaren tushe da dukan kauri shine Tsakiyar Cambrian. A cikin 2018, K. Karlstrom da sauransu  sun gano cewa Tapeats Sandstone ya fi ƙanƙanta fiye da yadda aka fassara a baya kuma ba ya zama ƙarami zuwa gabas. A sakamakon haka, Bright Angel Shale ya kasance gaba ɗaya a cikin Tsakiyar Cambrian.  
 Rukunin Tonto Group da Bright Angel Shale masu launi suna da sauƙin ganewa a matsayin jerin yanayin ƙasa a ƙarƙashin tsaunuka masu tsawo na Redwall Limestone (Redwall yana zaune a kan ɗan gajeren dutse mai tsayayya na Muav Limestone); Tonto Group kuma ana iya gani a gefen Granite Gorge na Kogin Colorado da Vishnu Basement RocksDutsen da ke ƙarƙashin Vishnu

## Dubi kuma

* Geology na yankin Grand Canyon
* Jerin sassan burbushin halittu a Arizona
* Paleontology a Arizona

## manazarta

## Ƙarin karantawa

* Blakey, Ron da Wayne Ranney, Tsohon Landscapes na Colorado Plateau, Grand Canyon Association (mai bugawa), 2008, shafuka 176,   
* Brandriss, M. (2004) Rashin daidaituwa tsakanin Proterozoic da Cambrian rocks, Grand Canyon, Arizona. GeoDIL, A Geoscience Digital Image Library, Jami'ar North Dakota, Grand Forks, North Dakota.
* Mathis, A., da C. Bowman (2007) Babban Zamanin Dutse: Zamanin Lamba don Dutse da aka fallasa a cikin Grand Canyon, Grand Canyon National Park, Arizona, National Park Service, Grand Canyon Nacional Park, Arizona.
* Share, J. (2102a) ''Babban rashin daidaituwa na Grand Canyon da Late Proterozoic-Cambrian Time Interval: Sashe na I - Bayyana shi.''
* Share, J. (2102a) ''Babban rashin daidaituwa da Late Proterozoic-Cambrian Time Interval: Sashe na II - Rifting na Rodinia da "Snowball Earth" Glaciations da suka biyo baya.''
* Timmons, M. K. Karlstrom, da C. Dehler (1999) Grand Canyon Supergroup Six Unconformities Make One Great Unconformity A Record of Supercontinent Assembly and Disassembly. Binciken kwata-kwata na Boatman. tashi. 12, No. 1, shafuffuka na 29-32.&nbsp;
* Timmons, S. S. (2003) ''Koyon Karanta Shafuka na Littafin'' (Grand Canyon Geology Training Manual) , National Park Service, Grand Canyon National Park, Arizona.