We’re pleased to welcome our latest contributer to Earth Science Erratics: Tim Sherry, a graduate student at McGill University. His first entry (cross-posted from Tim’s newly created geoblog, Up-Section), gives an account of a memorable stop on a recent field trip to Newfoundland. I’m already quite jealous, because this is somewhere that I’ve always wanted to visit. Amongst over geological wonders (including possibly the oldest Ediacaran fossils yet found), Newfoundland was also a key location in unravelling the existence of supercontinent cycles. Fossils and paleomagnetic measurements have revealed that the Precambrian, Cambrian and Ordovician rocks (between 600 and 450 million years old) at the coast were once on the other side of a large ocean basin from rocks of the same age further inland. They were mashed together a few tens of millions of years later in the continental collision that eventually formed the Appalachians.
Tim’s post focusses on Bell Island, and the iron ore deposits that are found there. As well as some lovely photos of the ore horizon, Tim delves into the history and practicalities of mining in the region, before looking more closely at the ore itself. It’s mysterious stuff, because its composed mostly of ooids made of iron oxide. Ooids are formed by mineral precipitation around sedimentary grains, producing their distinctive layered-onion structure in cross section. Most ooids are made of calcium carbonate and form in warm, shallow water. No-one has quite worked out how you precipitate hematite instead, but Tim gives some insight into the various theories that have been proposed.
Head over to Erratics for some good scenery, cool rocks, and mystifying mineralogy.
Nice plan for content warnings on Mastodon and the Fediverse. Now you need a Mastodon/Fediverse button on this blog.