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given the errors on the dates...

Posted by pike on 14 Jan 2016 at 20:31 GMT

...we are 95% confident that the volcano erupts twice between 19,000-43,000 years ago.

No competing interests declared.

RE: given the errors on the dates...

Sebi73 replied to pike on 15 Jan 2016 at 08:57 GMT

I see that you suggest that given the volcanoes uncertainty the spray shape signs could be much younger like the cave ...however our hypothesis is not solely based on the 40Ar/39Ar ages we obtained.
1) Volcanoes we are talking about are monogenic cone that produced several eruptions but within several months therefore a same cone cannot erupt twice. Of course considering the uncertainty we cannot tell it is 36000 ka but we suggested that because of the geochronological evidences in the cave itself (see below).
2) We have other information such as paleomagnetism and lavas superposition that suggest two periods on restricted between 30 to 40 ka and the other one between 15-20 ka. We dated 15 volcanic events in total and these data will be soon submitted.
3) Furthermore, it seems that you do not know all the literature concerning this region. Indeed on tephra layer was found in an Ardèche cave near the Chauvet-Pont-d'Arc few years ago (e.g. Aven du devès de Reynaud; see Debard and Pastre 2008). This tephra match in age and chemical composition the Suc du PAL (that we dated in this article). Base on 14C age this tephra give a age of 33.2 ± 1.5 ka (uncalibrated age. It means that volcanic material reached the Chauvet vicinity and that active volcanism existed between 35 and 38 ka.
4) The 14C date obtained on the rump of the megaceros proves that the spray shape signs below cannot be younger than 34 ka.
5) The goal of this article was to prove that volcanic activity existed during the 30 to 40ka period near the cave and to propose that the specific spray shape signs from the Pont-D'arc cave could represent strombolian eruptions. Even if the age of these signs is somehow younger and the volcanic eruptions too (we have doubt about that!) these representations will still be more than 10ka the older that the current oldest depiction of a volcanic eruption.

No competing interests declared.