Well, where are we today? At the beach?Yes, we would be if we were here sometime around 1.0 billion years ago. This is a close-up of a bed of conglomerate of the Signal Hill formation which outcrops along the eastern edge of the Avalon Peninsula in Newfoundland.
There are a couple of things these rocks tell us. First the red staining is from the mineral hematite, an oxide of iron. This means the rocks were deposited in a shallow water environment because when sediments are deposited in deep water they cannot oxidize as there's no oxygen. Second, the larger cobbles and pebbles indicate that there must have been fast moving water because slow meandering water doesn't have the energy to transport rocks of this size. Third the cobbles and pebbles appear to be well rounded, therefore they have been worked a bit in transportation as the sharp edges have been worn off.
As it turns out, in sandstone (finer grained rocks) above and below this conglomerate show signs of crossbedding so we can determine that they were laid down in flowing water and we can tell the direction the water was moving in. It is likely that these rocks were deposited in a delta type area with rivers flowing into it. Something like the Mississippi River delta today.
You can't see this type of detail of course from a kayak but I still like to do a little research and know something about the geology of where I paddle. I find the geology just as interesting as the wildlife. And, you don't need to be a geologist to appreciate the geology. Just the few things I've noted in this blog entry may help you identify interesting things in the rocks where you stop for lunch etc.
Tony :-)
Interesting Tony. Nothing like looking at a 1 billion year old delta. Would there be fossils in this type of rock or it's surroundings? I've found lots of fossils in BC on the rivers there. Where would be a good area here in NL to look for them? Any areas accessible by kayak? Maybe you'll want to email ME on this one! ;-)
ReplyDeletestAN
Stan, most people know about the trilobite site at Manual's River. There's also the world famous site at Mistaken Point just past Portugal Cove South and then there are various site in and around St. John's proper.
ReplyDeleteThe Mistaken Point site has fossil impressions of sea life that dates from 575 - 560 million years ago. These rocks are older and aren't fossiliferous.
Tony :-)