We woke up and lounged abound the property this morning before fueling up with porridge and heading east. Time for the Jurassic Coast!
The south coast of England holds 185 million continuous years of Earth history. A walk from west to east along the shore reveals progressively younger rocks: from Triassic to Jurassic to Cretaceous. This incredible scientific resource is now a UNESCO World Heritage Site and a bucket list item for geologists worldwide. Armed with books and maps we set out to battle the throngs of sun-loving holiday-goers, more concerned with tans and ice creams than strata and sedimentation. Philistines.
Wave action constantly batters the shoreline, exposing and subsequently destroying the fossil record. Researchers rely on ordinary citizens to comb the beaches for new discoveries after winter storms or landslides. And you get to keep what you find! (Within reason of course) The West Dorset Fossil Collecting Code of Conduct outlines the rules to keep people and the fossils safe.
The most famous fossil collector of all, Mary Anning was born on the Jurassic Coast. Here she discovered and collected some of the most famous specimens of the Mesozoic era. Of course Kat wanted to pay her respects. We began the day at Charmouth Beach, Anning’s home turf. Here Anning discovered plesiosaurs, ichthyosaurs and ammonites. Our ambitions were smaller. We spent the next few hours walking below the crumbling shale cliffs, splitting open rocks amongst the *clink clank* of happy families doing the same. We were content to bring home a few ammonites and a fish fin.
So why here? What’s the deal with the rocks? Glad you asked! During the Triassic Period the south coast of England was a desert with a few freshwater rivers providing a habitable ecosystem in the arid environment – think the Nile. Very few bones or bodies can survive a desert so fossil finds are rare. However rare they might be, the fossils found in these red sandstones are one of our best records of Triassic life.
Since the Jurassic coast spans 95 miles we opted to skip the Triassic sandstone and head straight for the early Jurassic. The region around Anning’s home town Lyme Regis and neighboring Charmouth record a very different environment. Here dark grey shales tell the story of a shallow sea bustling with life. Giant marine reptiles like ichthyosaur and plesiosaur preyed on smaller fish and sharks who ate the worms, ammonites, starfish, crinoids living on the seafloor. The mud on the seabed occasionally became anoxic – meaning there was no oxygen. Without oxygen, anything that fell on the seafloor could not decompose. Instead, the sea life was beautifully preserved as fossils.
The further east you head, the younger the rocks become. Since Kat could spend an entire day at a single outcrop, Colin shuffled her into the car for a longer drive 40 million years into the late Jurassic. Our destination was Lulworth Cove, a circular inlet swarming with tourists. Our prize was along the coast just west of the cove so we hoofed it across the beach, threading through the families and happy dogs. A few notes on the cove itself. The unique shape is due to the barrier of weathering-resistant limestone. The waves eat away the softer rock behind the limestone creating a perfectly circular cove. Those softer rocks include a beautiful white late Cretaceous chalk.
After walking around the cove, we ascended the limestone cliff on the far side to cross into the Lulworth Range military zone. During the weekday this area is off limits since it is an active shooty place. It being Sunday, we were able to explore the limestone cliffs overlooking the English channel. Here you can find one of the best preserved Jurassic forests yet discovered. When sea level dropped during the late Jurassic small islands formed between shallow lagoons. A vast forest of cypress, tree ferns and cycads grew along the shore. As sea level rose the saline water overcame the trees and the forest died. A thick mat of algae grew around the stumps and logs which trapped sediment, forming mounds or “burs”. Although there is no publicly accessible petrified wood, visitors are welcome to climb over these burs and imagine the ancient landscape.
We had the place to ourselves. Colin unpacked the drone and Kat poked around the chert and limestone beds. One of the geology surprises of the site was the jumbled mass of finely laminated limestone blocks above the fossil forest bed. These chunks of rock appear to have been deposited in a massive landslide. Kat’s later research identified them as the Broken Beds, a limestone and evaporite breccia.
After our full day of rock exploration, we drove to the town of Weymouth in search of some food. Unbeknownst to Kat, Colin had something specific in mind. Sticky toffee pudding! A delicious end to a beautiful day.