HARPOCERAS AMMONITE DISCOVERY
Holzmaden discovery of a naturally created wall interior decor hanging plate of gold on black decoration full of intriguing prehistoric harpoceras fossil shells
GOLD ON BLACK
The presence of iron pyrite on the surface of fossils of the posidonia black ‘jet’ shales was created by an anoxic environment. Because the benthic level of the sea lacked a great concentration of oxygen the biota of the oceans once deposited post-mortem on the seafloor did not decay quickly, oxygen-loving bacteria did not form and decay the tissue of sea creatures like the ammonites. Disc-like pyrite nodules indicate the anoxic environment of the Jurassic seas in this location. Low oxygen loving Algae formed and produced sulphates which released hydrogen sulphates as a by-product, further bacterial breakdown released sulphur which combined with iron minerals to form iron pyrite.
Holzmaden, Baden-Württemberg, lies near Stuttgart in south western Germany. It is noted for the European oil shales deposited on a sea floor during the Early Toarcian. Formations of finely laminated layers of oil shales and finely grained sediments intercalated with bituminous limestones, these are the Lagerstätten or Posidonia Shale (Posidonienschiefer) and named after the discovery of a bivalve the Posidonia bronni and was also initially named after this P. bronni bivalve. The Posidonia Shale out-crop in a number of locations in southwestern Germany, many layers near the village of Holzmaden where mined for bituminous shales for the production of electricity and cement.
Genus: Cephalopoda, Order Ammonitida, Family Hildoceratidae and Dactylioceras commune.
Geological Age: Palaeozoic era, Lower Jurassic period, Toarcian stage, approximately 180 million years.
Geological Origin: Holzmaden, Posidonia formation, Lagerstätten oil shales, South West Germany.
The fauna of the posidonia shales forms a myriad of Jurassic marine life of the Toarcian stage, at this point approximately one hundred and eighth million years ago the seas teemed with large vertebrate reptiles chasing prey. Among the prey of ichthyosaurs and plesiosaurs flying reptiles, the pterosaurs glided over the surface of the waters hopeful of a meal. below in the water column pelagic cephalopods hunted above floating crinoids a sub-form of animal looking like a plant with grasping arms reminiscent of a terrestrial flower and so known as the sea lilies and at the benthic levels crustaceans eked out an existence foraging early forms of worms borrowing through the low oxygenated sediments. Among these groups the ammonoids were prolific, this is evident in the fossil shales, as rare as the ancient fossils in the limited depositional layers around Holzmaden the huge shelled molluscs are represented in the shales in glorious detail and number.
FOSSIL DEPOSITION HISTORY
The fossil shales of the Jurassic (Toarcian stage approximately180 million years ago) period. Formed part of the ancient Tethys Ocean and the deposition of sediments creating the the oil shales and fossil therein were deposited and fossilised in an anoxic (lacking in oxygen) deep water environment. These shales contain rare fossils of the Jurassic. Marine vertebrate fossils, ichthyosaurs, plesiosaurs, ammonites (see our ammonites pages) and crinoids ( see our crinoids pages). The Holzmaden (Posidonia shale deposits) are of a worldwide importance because of the unique formation and the discovery of skin cover showing parts of fossilised fauna rarely seen in the fossil record generally. Only few fossil depositions have such an environment to finely preserve its fossil treasures. The Posidonia Shale fossils can be found at the Museum Hauff, Holzmaden, as well as museums around the world.
Fossil crinoids of the Poseidon shales featured by the fossil store in exhibitions around Britain and beyond. The plates make excellent features, the crisp detail of feathery floret arms, golden hues of ‘fools gold’ in the form of iron pyrite set contrastingly against black to very dark grey Holzmaden shale is delightful. These plates now a premier fossil decor feature are becoming increasingly more uncommon. The time is now for the collection of ammonoid plates from the Poseidon stable. The naturally formed and tactile shale containing shellfish of the Jurassic have arrived on the fossil interior scene. The striking complete phragmacone's (shells) of the enormous pelagic ocean molluscs are preserved and conserved beautifully in plate issues. The plates can be hung to create an accompaniment to or an alternative of the sea lilies of the Poseidon theme. We can form and supply from sublime fossil mountings an accent to match your interior. Contact us for more information.
Finally, in this section, we turn to display and conservation of the wall plates. If one wishes to exhibit, display or feature this specimen fossil the fossil store can create a hanging frame or stand to suit your decor, venue or theme. This can be achieved in several ways, refer to our classic range of mounted fossils, which can be reached from our website menu > interiors > ammonites on bases or > statements, sections. Here you may find mounts of bronze. We can also create lucite (clear acrylic or perspex) chrome, silvered, brass or black ebonised types. For more information on mounting this specimen, fossil contacts us, all our information can be found on our contact pages through our website.