Theory of unconformaties

Angular unconformity at Bacon Cove, Newfoundland between Precambrian and Cambrian sedimentary rocks representing a time gap of 10's of millions of year

An unconformity represents a time gap between two sets of geological formations. An angular unconformity occurs when the underlying beds are tilted from the horizontal, eroded for a period of time and new rocks are deposited on the eroded surface.

The beds underlying the conglomerate (coarse cobbles, pebbles and sand) layer are Conception group rocks that were laid down in the Precambrian. An exact age hasn't been determined because they do not contain fossils necessary to date them. They were laid down in a deep marine environment over a considerable period to reach a thickness of 7,000 feet. Uplifted, tilted, laid bare and eroded for 10's of millions of years, the sea eventually overtook the land and the Cambrian conglomerate was deposited. The Cambrian period began about 542 million years ago so that all happenned a considerable time ago.

What I find interesting is that over 542 million years ago there was sun shining on these rocks and what the would the world have looked like if I was able to stand here. There wouldn't have been any land vegetation or animals, just land and sea, waiting 542 million years for my visit.

Come to think of it, I have an unconformity in my life too. I completed a degree in geology in 1973, went on to make my living at something completely different and now have returned to something that was an interest many years ago.

Tony :-)

Close up of the Cambrian conglomerate. It looks like poorly poured cement. The large cobbles and pebbles indicates they were deposited rapidly in a shallow water or river estuary environment. I can surmise that because big rocks don't transport that far to deep water and because some are angular non-rounded. Rounding happens when the pebbles are worked by rolling so that the edges are worn off, and that takes time.