Tsarin Blytt-Sernander

Rarrabawar **Blytt-Sernander**, ko jerin, jerin lokutan yanayi ne na Arewacin Turai ko matakai  bisa ga nazarin tsaunuka na Danish da Axel Blytt (1876) da Rutger Sernander (1908). An haɗa rarrabuwa a cikin jerin yankuna na pollen daga baya wanda Lennart von Post, ɗaya daga cikin waɗanda suka kafa palynology ya bayyana.

## Bayyanawa
Heinrich Dau ne ya fara lura da yadudduka na peat a cikin 1829. Royal Danish Academy of Sciences and Letters ta ba da kyautar ga duk wanda zai iya bayyana su. Blytt ya yi la'akari da cewa an ajiye yadudduka masu duhu a lokutan fari kuma sun fi haske a lokutan danshi, suna amfani da kalmominsa *Atlantic* (mai dumi, mai laushi) da *Boreal* (mai sanyi, bushe). A cikin 1926 C. A. Weber  ya lura da sararin samaniya mai kaifi, ko *Grenzhorizonte*, a cikin peat na Jamusanci, wanda ya dace da rarrabawar Blytt. Sernander ya bayyana lokutan subboreal da subatlantic, da kuma lokutan glacial na ƙarshe. Sauran masana kimiyya tun daga lokacin sun kara wasu bayanai.

An tsara rarrabuwa kafin ci gaban hanyoyin da suka fi dacewa, kamar C-14 Dating da isotope ratio cycles. Masana ilimin ƙasa da ke aiki a yankuna daban-daban suna nazarin matakan teku, peat bogs, da samfurori na kankara ta hanyoyi daban-daban, da niyyar ci gaba da tabbatarwa, da kuma inganta jerin Blytt-Sernander. Sun sami cikakkiyar rubutu a duk faɗin Eurasia da Arewacin Amurka.

Canjin canjin yanayi ya fi rikitarwa fiye da yadda Blytt-Sernander periodizations zai iya ganowa. Misali, samfurori na baya-bayan nan a Roskilde Fjord da Lake Kornerup a Denmark sun gano nau'ikan pollen 40 zuwa 62 da za a iya rarrabewa, bi da bi.  Koyaya, ba a gabatar da samfurin maye gurbin da aka yarda da shi a duniya ba.

## Matsalolin

### Dating da daidaitawa
A yau an tabbatar da jerin Blytt-Sernander ta hanyoyi daban-daban na kimiyya, galibi kwanakin radiocarbon da aka samu daga peat. Ranar radiocarbon da ta gabata galibi ana barin su ba tare da daidaitawa ba; wato, an samo su ne ta hanyar zaton maida hankali ga radiocarbo na yanayi. Matsakaicin radiocarbon na yanayi ya bambanta a tsawon lokaci kuma don haka ana buƙatar daidaita kwanakin radiocarmon.

### Haɗin kai tsakanin horo
An yi amfani da rarrabawar Blytt-Sernander a matsayin tsarin lokaci don al'adun archaeological na Turawa da Amurka. Wasu sun tafi har zuwa gano matakai na fasaha a arewacin Turai tare da takamaiman lokuta; duk da haka, wannan tsarin sauƙaƙe ne wanda ba a yarda da shi ba. Babu wani dalili, alal misali, dalilin da ya sa ya kamata 'yan arewacin Turai su daina amfani da tagulla kuma su fara amfani da baƙin ƙarfe ba zato ba tsammani a ƙananan iyakar SubAtlantic a 600 BC. A lokacin zafi na Atlantic, al'adun Mesolithic sun mamaye Denmark, maimakon Neolithic, duk da shaidar yanayi. Bugu da ƙari, matakan fasaha sun bambanta sosai a duniya.

## Tsarin
Matakan Pleistocene da kimanin kwanakin da aka daidaita (duba sama) sune:

* Tsohon Dryas na filin wasa, 14,000-13,600 BP (Kafin Yanzu) 
* Allerød interstadial, 13,600-12,900 BP
* Matashi na Dryas a filin wasa, 12,900-11,640 BP

Matakan Holocene sune:

* Preboreal
* Boreal, sanyi, bushe, hauhawar zafin jiki, 11,500-8,900 BP
* Atlantic, dumi, danshi, matsakaicin zafin jiki, 8900-5700 BP
* Subboreal, 5700-2600 BP
* Yankin Atlantika, 2600-0 BP

## Nau'in alama
Wasu nau'ikan shuke-shuke masu alama ko nau'ikan da aka yi nazari a cikin peat sune

* *Sphagnum*
* *Carex limosa*
* *Scheuchzeria palustris*, Rannock rush
* *Eriophorum vaginatum*, ciyawa
* *Allurar rigakafin oxycoccos*, cranberry
* *Andromeda polyfolia*, rosemary
* *Erica tetralix*, mai laushi mai laushi
* *Calluna vulgaris*, heather
* *Pinus*, pine
* *Betula*, birch

Ƙarin sphagnum yana bayyana a lokutan rigar. Lokacin fari yana nuna karin bishiyoyi, na birch da pine.

## Manazarta