[Rockhounds] Obsidian in Michigan (Paul van den Bergen)

[Paul van den Bergen]

Ah yeah. that makes sense.

On Thu, 22 Sept 2022 at 02:23, Paul <etchplain at att.net> wrote:

> On Mon, Sep 19, 2022 at 7:05 PM <gbrown at catspaw-minerals.com> wrote:
>
>  > Hi Kids...
>  >
>  > I'm in a Facebook argument about obsidian in lower Michigan.
>  > They don't believe me when I say NOPE.
>  > *sigh*
>  > Gary
>
> I agree with Gary. The volcanic rocks of the Canadian Shield are much
> too old to contain and be a source of obsidian. Any obsidian that these
> rocks once contained have long since been either recrystallize to chert,
> altered to clay minerals and zeolites, and / or recrystallized by
> metamorphism.
>
> The occurrence of obsidian in Michigan is discussed in the below open
> access paper:
>
> O’Shea, J.M., Lemke, A.K., Nash, B.S., Sonnenburg, E.P., Ferguson,
> J.R., Nyers, A.J. and Riebe, D.J., 2021. Central Oregon obsidian from
> a submerged early Holocene archaeological site beneath Lake Huron.
> PloS one, 16(5), no.e0250840.
>
> https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0250840
>
> https://www.researchgate.net/publication/351720833_Central_Oregon_obsidian_from_a_submerged_early_Holocene_archaeological_site_beneath_Lake_Huron
>
> Yours,
>
> Paul H.
>
>
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-- 
Dr Paul van den Bergen