Dean Pearson
Douglas J. Nichols
Jacqueline Wood
Antoine Bercovici
2009
<p><span>The Cretaceous/Tertiary (</span>K<span>/</span>T<span>) </span>boundary<span> corresponds to one of the very few unique events </span>in<span> the geological record discovered to date, representing </span>a<span> single traceable timeline across the world. This timeline, coincident with the geochemical and mineralogical singularities caused by the impact of </span>a<span> large extraterrestrial body, is also coincident with the end-Cretaceous extinction event </span>in<span> </span>North<span> America. This precise timeline gives an ideal context for comparing the trends recorded by the different groups of the terrestrial fossil record during the </span>K<span>/</span>T<span> extinction event. However, </span>in<span> </span>southwestern<span> </span>North<span> </span>Dakota<span>, numerous studies conducted on excellent exposures of the </span>K<span>/</span>T<span> </span>boundary<span> showed that the geochemical and mineralogical </span>criteria<span> associated with the impact are rarely preserved. For that reason, palynology is preferred as </span>a<span> simple and efficient way for identifying the </span>K<span>/</span>T<span> </span>boundary<span>. </span>In<span> this context, </span>a<span> previously undescribed outcrop </span>section<span> from </span>southwestern<span> </span>North<span> </span>Dakota<span> was found to preserve an extensive record of the continental </span>K<span>/</span>T<span> </span>boundary<span> with miospores and plant megafossils, as well as microvertebrates and large vertebrate elements. Preliminary studies on the fossil associations recovered from this site showed an inconsistency between the Paleocene age given by the vertebrate and megafloral component and the Cretaceous age given by the </span>palynological<span> record. This issue is investigated </span>in<span> this paper, with </span>a<span> major emphasis on the description and analysis of the </span>palynological<span> record associated with sedimentological and paleoenvironmental data. Results shows that palynologically, the </span>K<span>/</span>T<span> </span>boundary<span> is placed more accurately using relative abundance variations of </span>selected<span> taxa. </span></p>
application/pdf
10.1016/j.cretres.2008.12.007
en
Elsevier
Biostratigraphy of selected K/T boundary sections in southwestern North Dakota, USA: Toward a refinement of palynological identification criteria
article