Devonian

How To Use Devonian In A Sentence

• The Early Devonian saw a decline to 20 genera, with a slow return by the end of the Pragian, a tectonically active phase marked by global sea level drawdowns, and provinciality.
• The fact that these rocks were not supplying detritus to the sedimentary basin is consistent with the geological observation that they always appear covered by the younger deposits, with little or no discontinuity until the Devonian.
• In the Lower Devonian, ammonoids appeared, leaving us large limestone deposits from their shells.
• The status of many Eurasian species of Late Devonian cyrtospiriferid brachiopods require careful restudy to properly assess their generic status and assignment to morphologic/phylogenetic groups of Cyrtospirifer outlined below.
• Variably serpentinized Devonian mafic and ultramafic intrusive rocks occur in the western and northern parts of the map area.
• Fossilized spinnerets (the organs that spit out the spider silk) that occur in Middle Devonian rocks in Schoharie County, New York, show that spiders have been making silk for at least 380 million years.
• The sequence comprises Lower Ordovician conglomerates and carbonates overlain by Upper Ordovician to Middle Devonian limestone with occasional phyllite and quartzite.
• As an independent check on the overall oxygen trend, it is notable that fusain is found for the first time in the Late Devonian.
• Certain ancient strata, known as the Devonian black shale, occupying the Ohio valley and the neighbouring parts of North America to the east and north of that basin, appear to be accumulations which were made beneath an ancient Sargassum sea. Outlines of the Earth's History A Popular Study in Physiography
• The allochthonous units that overlie the eastern part of this terrane were probably emplaced when the Magnitogorsk volcanic arc collided with this margin in late Devonian times.