CompuServe Messages

Hi, Jon– In Old Red Sandstone, I am pleased to have a name for proto-N.America + proto-Europe (Laurentia+Baltica), since I gather they were together for a long time before joining up with Pangaea. The Jan. 1995 Scientific American has a cover story proposing that Laurentia rifted away from proto-S.America ~550 million years ago; the coast that would eventually become the Appalachians separated from what is now Chile, more or less (modern Scotland would have been in the Arica embayment between Peru and Chile, more or less). It is suggested that Laurentia might have bumped S. America twice more while making and end run around it before being collected into Pangaea. In the mid-Ordovician, the eastern U.S. presumably hit Peru; in the late Devonian, they have the southeastern U.S. hit again near Peru or Ecuador (by this time it is really O.R.S., not just Laurentia). That last collision, in the late Devonian, would have corresponded to the Acadian orogeny, they figure. Is this the first orogeny you spoke of? Thus S. America would replace the "small exotic terranes" you spoke of, or perhaps they were island arcs caught in the squeeze. –Doug