Sub-Cambrian peneplain

Yankin sub-Cambrian shine tsohuwar, mai laushi sosai, yanayin rushewa (peneplain) wanda aka tono shi kuma ya fallasa shi ta hanyar rushewa daga ƙarƙashin Cambrian strata a kan manyan yankuna na Fennoscandia. Gabas, inda wannan peneplain ya nutse a ƙasa da Cambrian da sassan duwatsun rufe Paleozoic. Yankunan da aka fallasa na wannan peneplain suna da faɗi sosai tare da sauƙi na ƙasa da 20 m. Dutsen da ke rufewa ya nuna cewa teku mai zurfi sun mamaye peneplain a lokacin farkon Paleozoic. Kasancewa mafi tsufa da za'a iya ganewa a yankin sub-Cambrian peneplain ya cancanci zama na farko peneplain.

Arvid Högbom ne ya fara gano farfajiyar a cikin littafin 1910, tare da Sten Rudberg ya buga taswirar farko mai zurfi a shekara ta 1954. Karna Lidmar-Bergström ta inganta wannan taswirar tun daga shekarun 1980. 

 Yankin 
Yankin Sub-Cambrian ya shimfiɗa a matsayin kusan ci gaba da bel tare da gabar gabashin Sweden na kimanin kilomita  (430 mil) daga arewa zuwa kudu. Kusa da Stockholm da Hudiksvall peneplain yana da yawa ta kwari na hadin gwiwa kuma a Babban Tekun shine peneplain na Sub-Cambrian yana da tsawo sosai kuma ya lalace. Za'a iya gano ƙarin ciki a yankin ƙwanƙwasawa na Kudancin Sweden inda kwarin haɗin gwiwa suka rarraba shi. Yankin Sub-Cambrian a cikin yankin crestal na Kudancin Swedish Dome shine mataki mafi girma a cikin tsarin piedmonttreppen da aka gani a Småland. A kudancin Sweden, saman da ke kusa da shi ya karkata daga saman Kudancin Swedish Dome, zuwa arewa maso yamma a Västergötland, zuwa arewacin gabas a Östergötland da gabas a gabashin Småland. A wannan yanki na ƙarshe an yanke yankin sub-Cambrian zuwa yamma ta hanyar ƙayyadadden ƙira da kuma sanannen ƙira wanda ya raba shi daga yankin Kudancin Småland zuwa yamma. [A]
A cikin tsaunuka na tsakiya na Sweden, peneplain ya kara yamma yana da nisan kilomita  (mil 280) daga yamma zuwa gabas. Nan da nan gabas da kudancin tafkin Vänern peneplain ya karkata yamma da arewa bi da bi. Wannan yana nunawa a cikin cewa yankin kudu maso gabashin tafkin ba shi da zurfi amma yana ci gaba da zurfafawa zuwa arewa maso yamma. A Bohuslän, a arewacin iyakar Yammacin Yammacin Sweden, akwai wasu rashin tabbas game da ko tuddai sune Ragowar peneplain. Irin wannan yanayin yana faruwa a tsakiyar Halland .  Ƙarin yamma, an fassara wasu sassan Paleic a Norway don zama wani ɓangare na peneplain wanda aka ɗaga shi kuma a bayyane yake ya rushe ta hanyar kuskuren NNE-SSW. Kusa da tsaunin Hardangervidda mai tsawon mita 1,100 (3,600  a Norway shine filin Sub-Cambrian an ɗaga shi aƙalla mita 1,000 (3,300 ft),  duk da cewa Hardangervidta kanta wani ɓangare ne na ƙaramin filin da aka kafa a zamanin Miocene.
A Stöttingfjället a arewacin Sweden peneplain ya faru, sakamakon tasowa na tectonic, a kusan mita 650 (2,130 ft) yana ba da asali ga jerin gibin ruwa ciki har da na Ångermanälven, Indalsälven da Ljusnan. [1]
A arewa maso yammacin Finland Ostrobothnian Plain ci gaba ne na peneplain. A gabas da Sub-Cambrian peneplain ya ci gaba a matsayin rashin daidaituwa a ƙarƙashin Gabashin Turai. [B] A kan babban sikelin peneplain ba cikakke ba ne kamar yadda ya lalace. Wannan lalacewa shine amsawar isostatic ga rushewa da nauyin Phanerozoic sediments wanda ke sama da yawancin peneplain. Ana nuna alamar ta hanyar rashin inselbergs gaba ɗaya.   Ɗaya daga cikin banbanci ga wannan shine tsibirin Blå Jungfrun a cikin Tekun Baltic wanda shine tsohuwar inselberg da aka kafa a lokacin Precambrian kuma an binne shi a cikin sandstone bayan an kafa shi. Blå Jungfrun ya kasance an binne shi har sai rushewar Gabashin Turai ya 'yantar da shi a cikin 'yan kwanakin nan. Daga kudu maso gabas an gano jerin inselbergs da aka binne a saman peneplain ta hanyar nuna girgizar ƙasa a Lithuania.

 Asalin 
Fassara na sandstone na Jotnian ya nuna cewa yawancin Baltic Shield sun sami sauƙi tun daga Mesoproterozoic,   amma babu wani dutse da aka gano daga wannan lokacin da aka adana.  [C] Ƙananan ƙasa mai sauƙi wanda dutsen yashi na Jotnian ya ajiye ya damu da Sveconorwegian orogeny a yammacin Sweden kimanin shekaru miliyan 1,000 da suka gabata sannan ya fara sake lalacewa cikin ƙasa mai sauƙi.

Tsarin peneplain ya samo asali ne bayan shekaru miliyan 600 da suka wuce amma kafin zaluncin Cambrian . Duwatsun da ke cikin ƙasan da suka kafa saman peneplain an hako su daga zurfin inda zafin jiki ya wuce  kafin samuwar peneplain.  Karna Lidmar-Bergström da abokan aiki sun ɗauka cewa peneplain ya samo asali ta hanyar zagayowar zaizayar ƙasa tare da ɗan gajeren zangon kwari da ya gabata kuma ya kai matakin ƙasa zuwa wani tsohon matakin teku .   Saboda rashin ciyayi na ƙasa a zamanin Precambrian ana tunanin wanke takarda ya kasance wani muhimmin tsari na zaizayar ƙasa wanda ke haifar da samuwar pediments mai yawa. Wanke takarda zai kuma hana samuwar bayanan yanayin yanayi mai zurfi. Lallai, a wuraren da ɓangarorin ɓangarorin Sub-Cambrian ke kaolinized ba zai wuce ƴan mita a zurfin ba.  A cikin Finnmark na Norway, peneplain yana da ɗan lokaci tare da samuwar kaolinite, smectite da rashin sani har zuwa  a ƙasa da haɗin saman ƙasa tare da dutsen sedimentary na zamanin Cambrian. 

 Rufin dutse 
Flatness na peneplain yana nufin cewa a lokacin Cambrian transgression manyan yankuna sun cika da ambaliyar ruwa da sauri suna samar da manyan teku masu zurfi a cikin sauye-sauye. Sabon taimako da aka kafa a saman tsaunuka na Cambrian ya kwantar da rashin daidaito a cikin peneplain. Yankin yashi na farko na Cambrian da ke rufe peneplain a kudancin Norway, Scania da Bornholm tabbas ba a sake amfani da su ba. Wannan yana nufin duwatsun iyaye na sandstone sun lalace kuma an sake yin Laifi da karfi kuma ya kai ga balaga ba tare da wani mataki ko hiatus ba. Yankunan tushe na waɗannan sandstones sune duwatsu na gida daga Transscandinavian Igneous Belt ko Sveconorwegian da Gothian orogens.

 Manazarta 

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