Orcadian Basin

The Orkadischen lakes were a number of lakes that existed during the Devonian in the region of present-day Scotland, the Orkney and Shetland the.

The they left behind sedimentary rocks are part of the front of about 410 to 370 million years ago deposited Old Red Sandstone and has been studied by geologists and paleontologists since the 1830s. The rocks contain a variety of well-preserved fossils, most notably the remains of fish, which provide an insight into the development of the fish during this time.

Landscape

The landscape of the Devonian to these lakes consisted of rounded hills, which consisted of older metamorphic and igneous rocks. Extent and depth of the lakes fluctuated with time, so that the water sometimes reached up to the hills, and at other times so far receded that the opening into the lakes rivers could develop flood levels. In Stromness stromatolites were found, allow conclusions on a temporary salinization of lakes. In addition scolecodonts let (pine elements of living in the sea extinct annelids ) that were found in the Eday - marls, the conclusion that the lakes at least temporarily had a direct connection to the open sea.

The hills were without any vegetation, because the mainland was not covered by plants that were developing at this time. The erosion was therefore strong and probably seasonally variable, as well as the production of biomass in the lakes. This is reflected in the training of, resulting from deposited in the deep sea area lime slurry, limestone, which have a fine harness, which is interpreted as Warvenschichtung.

Fauna

Some live in the shore fishes exaggerated after her death to the center of the lake and sank to the bottom, where they remained under the anoxic conditions at depth. Most of these fish fossils have been found in Achanarras quarry near Thurso. At least one copy of the following list of fish orders was found there.

Flora

Very few plant fossils have been found in the Devonian rocks, and none of them live in position. There is evidence for the activity of algae and bacteria.

Varve Anoxic waters List of fossil sites
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