Oldest Dryas

The Oldest Dryas was a climatic period, which occurred during the coldest stadial after the Weichselian glaciation in north Europe. In the Alps, the Oldest Dryas corresponds to the Gschnitz stadial of the Würm glaciation. The three “Dryas” periods (younger, older, oldest) are named for a marker species, Dryas octopetala, detected in core samples of glacial ice and peat bogs. The Oldest Dryas corresponds to pollen zone Ia.Grassland (Inner Mongolia)Artemisia vulgarisBetula nanaDryas octopetalaGavia arcticaPodiceps nigricollisCygnus cygnusAquila chrysaetosGlacial streamLota lotaSalmo truttaSalvelinusMicrotus oeconomusMicrotus arvalisLepus timidusMarmota marmotaLynx (or Felis) lynxAlopex lagopusCanis lupusIcelandic horse, perhaps like Equus ferusRangifer tarandusCapra ibexWoolly rhinocerosMammoth The Oldest Dryas was a climatic period, which occurred during the coldest stadial after the Weichselian glaciation in north Europe. In the Alps, the Oldest Dryas corresponds to the Gschnitz stadial of the Würm glaciation. The three “Dryas” periods (younger, older, oldest) are named for a marker species, Dryas octopetala, detected in core samples of glacial ice and peat bogs. The Oldest Dryas corresponds to pollen zone Ia. The period was between 16,050-13,050 BC, from Roberts, 1998. A date from Kilkeel, Northern Ireland, extends the start of the period to as early as 17,050 BC. A strong sequence of carbon-14 dates derived from layered material in the Hauterive/Rouges-Terres excavations on the northwest shore of Lake Neuchâtel in Switzerland, 1992–1993, places the end of the Oldest Dryas at about 12,700 BC, calibrated. The same date from Antarctica and the south China sea is 14,600 and 14,700, respectively, and a Greenland ice core indicates 14,500. David Miles refers to the Oldest Dryas as the last Heinrich event (H1) and dates it to between 16,500 and 14,500 years ago. The ultimate standard to which all these dates are to be compared is the graph of the oxygen isotope ratio cycles, which gives change in isotope concentration on the y-axis, with time on the x-axis. The graph plots many events that are sharply defined, but others are not. The selection of a terminal point is sometimes partially arbitrary. The end of the Oldest Dryas is sharply defined. The beginning is a long, gently sloping band, probably no earlier than 17,050 BC, but the date might be set later by approximately 1000 years. Data derived from isotope variation of nitrogen and argon trapped in Greenland ice gives a high-resolution date for the end of the oldest Dryas at the sharp temperature rise of 14.67 ky BP. The complete sequence of late Pleistocene climatic periods, defined for Northern Europe, are the Oldest Dryas (stadial), the Bölling (interstadial), the Older Dryas (stadial), the Allerød (interstadial), and the Younger Dryas (stadial). The Holocene begins immediately afterward. The last three are also Blytt-Sernander periods. Sometimes, the Older Dryas is missing, as in the Jura Mountains of France, or it is negligible in the evidence. In that case, the initial part of the sequence appears to be Oldest Dryas (cold), Bølling-Allerød (warm), Younger Dryas (cold). The Bølling-Allerød corresponds to the Windermere interstadial in Britain. Often, however, the apparently-missing Older Dryas is a problem of resolution in the evidence. Some scientists have undertaken high-resolution studies, which combine a variety of climatological methods. They, like the ones conducted on Owens and Mono Lakes, in California, usually detect the Older Dryas. Even when it is detected, it appears to be no more than a few centuries of slightly-cooler weather on the oxygen isotope ratio graph. During the Oldest Dryas, Europe was treeless and similar to the Arctic tundra, but much drier and grassier than the modern tundra. It contained shrubs and herbaceous plants such as the following: