tag:blogger.com,1999:blog-5859094080858570248.post2017997582007089512..comments2024-03-28T13:00:43.523+05:30Comments on Rapid Uplift: K-Pg Mass Extinction: Asteroid Impact Opponents Are Not Giving UpSuvrat Kherhttp://www.blogger.com/profile/18281172632784780810noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-5859094080858570248.post-44456079097343147632010-03-31T23:36:43.056+05:302010-03-31T23:36:43.056+05:30Brian's reading is correct. Keller's group...Brian's reading is correct. Keller's group has maintained that Chicxulub was one of the factors in the extinction but not the sole one.<br /><br /><i>the Keller group propose impact-deterioration-boundary (or possibly deterioration-impact-deterioration-boundary).</i> <br /><br />or maybe deterioration-impact-deterioration-impact (boundary). the Ir anomaly at the boundary has to be explained. if the Brazos stratigraphic measurements and interpretations of Keller are correct and there is really no pronounced Ir anomaly associated with the Chicxulub impact what caused the Ir anomaly seen at the K-Pg boundary?Suvrat Kherhttps://www.blogger.com/profile/18281172632784780810noreply@blogger.comtag:blogger.com,1999:blog-5859094080858570248.post-43512221283770048612010-03-31T21:34:14.270+05:302010-03-31T21:34:14.270+05:30I also get somewhat confused when reading these pa...I also get somewhat confused when reading these papers. Anyone know of a good review of all the plausible hypotheses? Something that doesn't necessarily conclude one way or another? Might be a good project for a science writer/blogger.BrianRhttp://clasticdetritus.comnoreply@blogger.comtag:blogger.com,1999:blog-5859094080858570248.post-61600039025341007962010-03-31T20:55:21.613+05:302010-03-31T20:55:21.613+05:30Isn't the argument over relative timing? I was...Isn't the argument over relative timing? I was under the impression that it's generally accepted there was some degree of climatic deterioration at the end of the Cretaceous, which contributed to the extinction: but whereas the more popular chronology is deterioration, then the Chicxulub impact marking the K-Pg boundary, the Keller group propose impact-deterioration-boundary (or possibly deterioration-impact-deterioration-boundary).Chris Rhttps://www.blogger.com/profile/10923865059164569384noreply@blogger.comtag:blogger.com,1999:blog-5859094080858570248.post-45937588401918595522010-03-31T20:29:46.191+05:302010-03-31T20:29:46.191+05:30Here is an excerpt from Prauss' abstract:
&qu...Here is an excerpt from Prauss' abstract:<br /><br />"These data [climate/oceanographic proxies] suggest that prominent, high frequency palaeoenvironmental changes precede the K/Pg boundary, which is inconsistent with a single "catastrophic" impact as the cause for the K/Pg boundary event. However, according to the onset and distinct distribution of the peak abundance of trilete spores, the base of the ED [event deposit] may actually reflect the Chicxulub impact, which probably contributed significantly to K/Pg boundary crisis within the biosphere."<br /><br />Unless I'm reading this wrong, he's saying that the impact did indeed contribute to the extinction -- just that it wasn't the sole cause. <br /><br />I think this is an important aspect of this debate. All too often single-factor explanations are pitted against each other.BrianRhttp://clasticdetritus.comnoreply@blogger.comtag:blogger.com,1999:blog-5859094080858570248.post-62331137912625512112010-03-31T20:09:50.108+05:302010-03-31T20:09:50.108+05:30Based on previous work on Brazos , Keller et al cl...Based on <a href="http://geoweb.princeton.edu/people/keller/Keller_et_al_2007_EPSL_Brazos.pdf" rel="nofollow">previous work on Brazos </a>, Keller et al claim that no pronounced Ir anomaly is associated with the spherule layer or the overlying event deposits. They take it to indicate that the Chicxulub asteroid was not Ir enriched! Their work does show a more Ir anomaly coincident with the K-T boundary as defined by C13 shift and first Danian formaminifera. That they have interpreted as having caused by another impact!Suvrat Kherhttps://www.blogger.com/profile/18281172632784780810noreply@blogger.comtag:blogger.com,1999:blog-5859094080858570248.post-82505390913319242192010-03-31T19:14:52.382+05:302010-03-31T19:14:52.382+05:30I've found the work supporting the event depos...I've found the work supporting the event deposit (vs. the Keller group interpretations) to be plausible and even convincing when combined with all of the other evidence. But this work (the Prauss paper) complicates things. The response should be interesting. Also, I agree with CJR that we should really know where the Ir anomaly sits in this section.CMhttps://www.blogger.com/profile/11644474060200286294noreply@blogger.comtag:blogger.com,1999:blog-5859094080858570248.post-76276099713950299192010-03-31T18:16:56.405+05:302010-03-31T18:16:56.405+05:30What puzzles me about this whole dispute is that I...What puzzles me about this whole dispute is that I can't see any attempt in this paper to look for the iridium anomaly. Surely that would help to estimate the timescale of deposition, by seeing if it confined to the very bottom or spread through the whole sequence?Chris Rhttps://www.blogger.com/profile/10923865059164569384noreply@blogger.com