Re: dropstones

Jonathan Clarke (
Fri, 02 Apr 1999 07:15:21 +1000

Hi David

Debris flows usually have other evidence for their presence, such as disrupted,
contorted, and chaotic bedding.

When we talk about vegetation rafting we should not forget sea weeds. Most
pebbles found on otherwise sandy beaches are rafted there attached to seaweed

God Bless


David Campbell wrote:

> >>I have seen quite a few dropstones of all sorts, including examples I
> >have
> >>interpreted as glacial, volcanic projective, impact projectile, and
> >vegetational rafting.
> Debris flow is another possible source of stray larger rocks in a
> fine-grained setting. I vaguely recall a paper on such material from
> Jamaica, probably with reference to the Bowden (Pliocene).
> Also, it seems likely that a few pebbles can be transported by rare
> episodes of higher energy in a normally quiet setting. Two weekends ago I
> found a small pebble in fine-grained fossiliferous Yorktown Formation
> deposits here in North Carolina. It was close enough to the ancient
> shoreline to have relatively easy transport of an occasional river pebble,
> but I do not know what to look for that would be diagnostic of its history.
> David C.