This study documents the terrestrial palynological record at the John's Nose section, a new Cretaceous—Paleogene (K—Pg) boundary site in North Dakota, USA. In addition to Mud Buttes and Pyramid Butte, John's Nose represents the third K—Pg section in southwestern North Dakota that preserves direct evidence of the Chicxulub asteroid impact, allowing for direct comparison over the timing and trends of the palynological record in respect to this event. The palynological analysis of John's Nose section reveals the presence of 68 pollen and spore taxa. Immediately above the boundary clay, a high abundance of fern spores of the genera Cyathidites and Laevigatosporites is recorded (with 59% of the assemblage being represented by Cyathidites). This very distinctive K—Pg ‘fern spike’ event is correlated with the devastation of land plants immediately following the asteroid impact and matches the composition generally reported from other sites in southwestern North Dakota. Palynostratigraphy demonstrates that the placement of the K—Pg boundary based upon the identification of the Last Appearance Datum (LAD) of typical Maastrichtian taxa (K-taxa) may be misleading. The presence of occasional K-taxa up to a few meters above the boundary clay at John's Nose represents an important difference when compared to previous reports. In light of this observation, LADs should be used cautiously as the primary criteria to identify the boundary; some K-taxa may have a short-term presence in the earliest Paleogene, or be reworked. In the John's Nose section, major changes and extinction in the palynological record occur at the geochemical K—Pg boundary, indicating that a catastrophic turnover took place over a short time.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 36 • No. s1