Late Devonian Mass Extinction: Conodonts

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Late Devonian Mass Extinction: Conodonts

Introduction
The Late Devonian mass extinction that takes place at the Frasnian-Famennian boundary is considered as one of the Big 5 mass extinctions (McGhee, 1998). Life at this time experienced huge losses among many different marine groups such as: brachiopods, molluscs, trilobites, conodonts, fish, as well as other organisms. In order to pinpoint a cause for the mass extinction both physical and geochemical processes have been looked at. The usual suspects such as ocean anoxia, volcanism, icehouse climate, and even bolide impacts have all been considered throughout the literature (Belka and Wendt, 1991; Joachimski and Buggisch, 2002; Joachimski et al., 2009; McGhee, 1998). In some of these studies, …show more content…

The Ordovician actually saw greater amounts of origination, but the Devonian has been assigned more biozones than the former (Boardman, 1983). Also interesting about the conodonts origination rates is that the rates were only higher that extinction rates for two periods of time, first at their origination in the Cambrian, and second in the late Silurian right before the Devonian (Clark, 1983) [Figure ?]. However, the key to the conodont extinction is that at the Frasnian-Famennian boundary the biggest discrepancy between the origination rate and extinction rate existed. This gap between rates showed in the fossil record as the conodonts took their biggest hit in abundance with around 89% of total genera going extinct (McGhee, 1998). After the mass extinction, the extinction rates did decline, but naturally so did origination rates. The conodonts were able to continue existence throughout the Paleozoic into the Triassic, but they never reached the same amount of prominence that they had before the mass extinction. The conodonts finally met their end during the Triassic-Jurassic and fell out of the fossil record completely (Clark, 1983). When looking at figure ?, you might notice that the conodonts experienced a sharp decline in origination at the end Ordovician mass extinction. The reason why they recovered though is because a gap never existed between the origination and …show more content…

The linguifomis biozone is still the last biozone of the Frasnian, and the triangularis biozone is still the first biozones of the Famennian as previously described in previous biozone assignments (asdfsadf). This example shows how well radiometric dating and biostratigraphy can work together when done properly. It seems that radiometric dating continues to undergo advancements and the biozones do a great job setting the scale for the rest of the Devonian. The Kaufmann biozonation uses ID-TIMS to create radiometric age markers and then used conodont biozones to refine the time

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