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,
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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
Stroud, M.M., Markwort, R.J., and Hepburn, J.C. (2009) Refining Temporal Constraints on Metamorphism in the Nashoba Terrane, Southeastern New England, Through Monazite Dating. Lithosphere, vol. 1, p. 337-342.
The shelf-edge includes carbonate-to-clastic facies transition and tectonic uplift and erosion of the carbonates followed by deposition of the clastics. The Saint Peter Sandstone is a well-sorted, almost pure quartz arenite deposited during a major mid-Ordovician low stand. Clastics spread across an exposed carbonate platform by transportation. This is shown by the well-rounded, frosted texture of the quartz grains.
Around 144 million years ago, began the emergence of the Ornithischian dinosaurs during the cretaceous period and diversified into North America and Asia.
It's hard to say that humans haven't had an impact on their environment. Climate change, for example, has been a hot issue in the developed world ever since evidence proving the existence of human-caused global warming was unleashed leading to an onslaught of theories regarding its potential effect on our future. But what impact did humans have thousands of years ago when they were first colonizing North America?
2. Clarke, Tom. “Chaos killed the dinosaurs.” Nature 28 June 2011 Nature News Service/ Macmillan Ltd 2015
Even though the study of the deterioration of pteropods in high acidity water may seem unimportant in the grand scheme of the ocean, it is crucial to start somewhere. In this case the pteropods happen to be one of the most obvious examples of marine life that will be influenced by the ocean acidification. It is without a doubt clear that ocean acidification is an up and coming problem that will change the chemistry of the ocean and not only the effect the ocean’s ecosystem and creatures, but most likely the rest of the environment as well. Even though there is copious amounts of research available concerning ocean acidification, it is unclear whether model predictions will come to fruition in the future, or if actual results will completely differ from projections. Currently, the only clear path to try to delay the progression of ocean acidification is to reduce carbon dioxide emissions exponentially. The chart below (Fig. 5) gives a concise and detailed account of what is happening, what will happen and what needs to happen if ocean acidification is going to be
Fig.6 showing a map of Earth during the Devonian period. Yellow star showing Anglesey. http://eeos260-f13-poynton.wikispaces.umb.edu/-/Ancient%20Wiki%20Project/Grp10%20Devonian%20and%20Silurian%20Periods/
The depositional environments at the time were largely influenced by tectonic setting changing multiple times during the Late Jurassic into the Late Cretaceous. Between the Late Jurassic and Early Cretaceous the regions tectonic setting changed from a transtentional system to a strike-slip system. This period is characterized by deep limestone deposits and shallow to intertidal seamounts and platform calcarenites (Catalano et al., 1998; Cirilli et al., 1999; Bellanca et al., 2002). In the Late Cretaceous, there’s a change from the strike-slip phase into an extensional phase, along with the normal faults of the African paleomargin becoming reactivated, possibly due to the change in motion between the African and European plates (Tortorici et al., 2001). Basin sedimentation continued into the Late Cretaceous following the normal fa...
They ruled the world before the time of the dinosaurs, from the Cambrian Period to the
...nder, C., Tsai, C., Wu, P., Speer, B. R., Rieboldt, S., & Smith, D. (1998/1999/2002). The permian period. Informally published manuscript, Biology 1B project for Section 115, University of California Museum of Paleontology, CA, Retrieved from http://www.ucmp.berkely.edu/permian/permian.php
Han, J., Zhang, Z. F., & Liu, J. N. (2008). A preliminary note on the dispersal of the Cambrian Burgess Shale-type faunas. Gondwana Research, (1), 269-276. doi:10.1016/j.gr.2007.09.001
There are several theories about how the Cambrian Explosion started. There were major changes in marine environments and chemistry from the late Precambrian into the Cambrian, and these also may have impacted the rise of mineralized skeletons among previously soft-bodied organisms. One theory as to what happened is that oxygen in the atmosphere, with the contribution of photosy...
Over the past century, the Burgess Shale has revealed important information about the development of earth’s history. The excavation of the Burgess Shale formation provided evidence for what was once just a theory in evolution. The taphonomic findings of the Burgess Shale have played a significant role in understanding the large diversity that resulted from the Cambrian explosion, advancing the study of evolutionary assemblages for Paleontologists worldwide.
seems like it happened so sudden, as geologic time goes, that almost all the dinosaurs
Radiocarbon dating is used to tell how old something is. When some normal carbon gets hit by the rays of the sun it turns into carbon 14. Plants absorb this radioactive carbon in the form of carbon dioxide. Animals receive this carbon from eating the plants. When the organism is dead it loses the carbon 14. Scientists can tell how old something is based on the amount of carbon 14 in a dead object. Carbon dating is accurate if the amount of carbon 14 in the atmosphere has remained the same throughout time. The second is if carbon 14 has always decayed at the same