Tsofaffin Dryas

Tsohon Dryas wani lokaci ne mai sanyi (sanyi) tsakanin Bølling da Allerød interstadials (saukan zafi),  kimanin shekaru 14,000 Kafin Gabatarwa, zuwa ƙarshen Pleistocene . Ba a fayyace kewayon kwananta da kyau ba, tare da kiyasin ya bambanta da shekaru 400, amma an yarda cewa tsawon lokacin ya kasance kusan ƙarni biyu.

Rashin zafi a hankali tun lokacin Last Glacial Maximum (shekaru 27,000 zuwa 24,000 BP) an katse shi da sanyi biyu: Tsohon Dryas da Matasa Dryas (c. 12,900-11,650 BP). A arewacin Scotland, kankara sun fi kauri kuma sun fi zurfi a lokacin Tsohon Dryas fiye da Younger Dryas da suka biyo baya, kuma babu wata shaida game da aikin ɗan adam na Burtaniya. A Arewa maso yammacin Turai akwai kuma Tsohon Dryas na baya (18.5-17 ka BP 15-14 ka BP).  Ana kiran Dryas ne bayan wani nau'in mai nuna alama, tsire-tsire na Arctic da Alpine Dryas octopetala, wanda aka samo ragowar a cikin mafi girma a cikin ajiya daga lokutan sanyi.

Tsohon Dryas ya kasance mai sanyi, lokacin Blytt-Sernander mai bushewa, wanda aka lura a cikin shaidar yanayi a wasu yankuna kawai,  wanda ya dogara da latitude. A yankunan da ba a kiyaye shi ba, ana ɗaukar Bølling-Allerød a matsayin lokaci guda. Shaidar Tsohon Dryas ya fi karfi a arewacin Eurasia, musamman wani ɓangare na Arewacin Turai, kusan daidai da Yankin Pollen Ic.

 Ranar da aka yi 
A cikin rikodin isotope na oxygen na Greenland, Tsohon Dryas ya bayyana a matsayin tudu mai saukowa wanda ke kafa karamin rata tsakanin Bølling da Allerød. Wannan tsari yana gabatar da wahala wajen kimanta lokacinsa, saboda ya fi wani batu fiye da wani sashi. Sashe yana da ƙanƙanta don tserewa daga ƙudurin mafi yawan jerin carbon-14, saboda maki ba su da kusanci sosai don samun ɓangaren.

Ɗaya daga cikin hanyoyin da za a iya amfani da shi ga matsalar yana ba da ma'ana sannan ya zaɓi wani sashi na son rai. Tsohon Dryas wani lokacin ana ɗaukarsa "tsakiya" kusa da 14,100 BP ko kuma ya kasance tsawon shekaru 100 zuwa 150 "a" 14,250 BP.

Hanyar ta biyu tana samun carbon-14 ko wasu kwanakin kusa da ƙarshen Bølling da farkon Allerød kamar yadda zai yiwu sannan ya zaɓi wuraren da suka dogara da su: misali, 14,000-13,700 BP.

 Bayyanawa 
Arewacin Turai ya ba da sauyawa na tsaunuka da wuraren tundra dangane da layin permafrost da latitude. A cikin yankuna masu laushi, a kusa da tabkuna da rafi, akwai bishiyoyi na dwarf birch, willow, buckthorn na teku, da juniper. A cikin kwarin kogi da tsaunuka, a kudu, akwai gandun daji na birch.

Itacen farko, birch da Pine, sun bazu zuwa Arewacin Turai shekaru 500 da suka gabata. A lokacin Tsohon Dryas, kankara ta sake ingantawa, kuma bishiyoyi sun koma kudu, don maye gurbin su da cakuda ciyawa da nau'ikan alpine masu sanyi. An kira wurin "Park Tundra," "Arctic tundra,"" "Ar Arctic pioneer vegetation," ko "birch woodlands". "Yanzu yana cikin canji tsakanin taiga da tundra a Siberia. Sa'an nan kuma, ya shimfiɗa daga Siberia zuwa Biritaniya, a cikin wani yanki mai zurfi.

 Manazarta