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1:250 000 Geological Map
This range of geological maps show the general geology of the area, they come in either folded (for taking on the field), or flat (for wall mounting)
Buy from UKGE |
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1: 50 000 Geological Map
This range of geological maps show the localised geology, they come in either folded (for taking on the field), or flat (for wall mounting)
Buy from UKGE |
Jurassic
GEOGRAPHY AND CLIMATE: Gondwanaland continues to break up, Graywacke,
shale and siliceous sediments formed. Continued mountain building.
mild, moist climates over most of the land.
TERRESTRIAL ANIMAL LIFE: Reptiles dominant with Crocodiles, turtles,
lizards and dinosaurs. Pterosaurs and Archaeopteryx take to the air.
Mammals begin to diversify. More advanced insects such as flies.
PLANT LIFE: Cycads, ginkos, conifers, ferns and tree ferns.
SEA LIFE: All major invertebrate groups well represented, ammonites and bivalves successful. Marine reptiles, Ichthyosaurs are Plesiosaurs.
Cretaceous
GEOGRAPHY AND CLIMATE: Seas flood half the land, Great thickness of
chalk, single-celled animals laid down. Land masses
begin to move towards their present positions. Climate mild without
extremes.
TERRESTRIAL ANIMAL LIFE: Advanced dinosaurs such as duck-bills. Turtles,
snakes,salamanders. Gulls and wading birds. Opossums & other mammals.
All dinosaurs and many other large reptiles extinct by the end of
the period.
PLANT LIFE: Gymnosperms, sequoias and cypresses. Flowering plants appear,
magnolias and oaks.
SEA LIFE: Plankton, coral reefs, rudists, ammonites, calcareous algae.
Marine reptiles and ammonites extinct by the end of the period. |
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Geological Guide to Charmouth
Black Ven - As soon as you enter the beach, to the West the Birchi Nodules are seen in the low cliff, it has been known in times of extreme low tide, that traces of a submerged forest including bones of mammoth and red deer can be revealed. The bones have been found close to the Western groyne.
Black ven
Just below the Birchi nodule layer, the bed of Shale's with Beef occur, this bed has many common ammonites including Arnioceras, Cymbites and Coroniceras. Occasional teeth and bones of ichthyosaurs including many other reptiles can be found. It is often the case that landslips at Black Ven will expose these beds and regular tides will keep the beds fresh. The upper beds from the beef and shale's can be found at Stonebarrow, just below beach level.
Walking West, you eventually come to Church Cliffs, for more information on the Blues Lias of Church Cliffs, please refer to Lyme Regis.
Stonebarrow - The upper most beds of Stonebarrow consist of Late Greensand, where occasional ammonites may be found. A 12m bed of Gault follows over lying Eype clay. 20m of Green ammonite beds overlay 23m of Belemnite marls. The black ven marls are around 50m reaching beach level. Just below beach level, Birchi nodules can be found at about halfway up Stonebarrow hill. The Birchi nodules can be split to find good condition ammonites and shells.
Stonebarrow cliffs
Within the Black ven marls, a layer of Stonebarrow flatstone is celebrated for its fine specimens of Asteroceras turneri, often preserved in yellow and brown calcite. Insects of beetles, grasshoppers, water-bugs, dragonflies and occasional plant remains can be found in these flat stones. The shale's are richly fossiliferous with ammonites, insects and fish remains. The crinoid, Pentacrinites fossilis is often magnificently preserved within this bed. 10m above the Flatstone is a line of nodules called the Stellare Nodules, the common Ammonite, Asteroceras stellare is often found.
The Belemnite Marls are bluish-grey marls. The marls are famous for Belemnites , although ammonites are common including, Tropidoceras, Platypleuroceras, Beaniceras and Apoderoceras. At the top of this bed is a limestone called the Belemnite Stone, full of Belemnites, Ammonites, bivalves and some rhynchonollids.
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