The Global Boundary Stratotype Section and Point for the base of the Danian Stage (Paleocene, Paleogene, “Tertiary”, Cenozoic): auxiliary sections and correlation

Abstract

Tunisia, Zumaya in Spain, Brazos in USA and Stevns Klint in Denmark), the chairwoman of the K/Pg Boundary Working Group submitted a written proposal to the International Commission on Stratigraphy (ICS). The GSSP of the K/Pg boundary was defined at the base of the boundary clay at the section near El Kef, Tunisia. This proposal was approved by the ICS in 1990 and was ratified by the International Union of Geological Sciences in 1991. Nevertheless, its publication in a prestigious stratigraphical journal of wide distribution, which is the final step in the definition of the GSSP, was not made until the chairman of the International Subcommission on Paleogene Stratigraphy (ISPS), in collaboration with several colleagues, including the chairwoman of the K/Pg Boundary Working Group, reviewed the studies since the original proposal and revised the main criteria defining the K/Pg boundary (Molina et al. 2006). However, this official publication of the GSSP did not include any auxiliary sections in which the event could be studied in other facies and different paleobiogeographic contexts, allowing a global correlation. Furthermore, deterioration of the outcrops at the El Kef section (Remane and Adatte, 2002), which makes necessary to trench and difficult to find the GSSP, requires assigning auxiliary sections where the K/Pg boundary is better exposed. The aim of this paper is to describe the most suitable sections, which are considered auxiliary sections of the K/Pg boundary, to establish the correlation between areas distal and proximal to the Chicxulub meteorite impact site and to solve problems of erroneous placement of the K/Pg boundary. Auxiliary sections According to Remane et al. (1996), the auxiliary sections proposed here are subordinate to the GSSP and fulfill most of the requirements to characterize a GSSP. The auxiliary sections described below are located in three different regions across the world (Fig.1): around El Kef (Tunisia), where the GSSP was defined (Aïn Settara and Ellès), in southwestern Europe where other suitable sections were proposed (Bidart, Caravaca, Zumaya) and around the Gulf of Mexico, close to the meteorite impact crater (Bochil and El Mulato). The Global Stratotype Section and Point (GSSP) for the Cretaceous/Paleogene (K/Pg) boundary was defined at the base of the boundary clay at a section near El Kef, Tunisia, but the outcrop became quite deteriorated. In order to better characterize the boundary and to solve problems of correlation, several auxiliary sections are designed and described in detail including: Aïn Settara and Ellès in Tunisia, Caravaca and Zumaya in Spain, Bidart in France and El Mulato and Bochil in Mexico. These sections are the most continuous, expanded and representative of marine sedimentation in areas proximal and distal to the Chicxulub meteorite impact site. In addition, these sections are classical, very well known, physically accessible, have been exhaustively studied and allow a very detailed global correlation. The correlation criteria used were the meteorit...

Geophysical Characterization of the Chicxulub Impact Crater

“…In the seismic profiles, we have mapped the base of the post-impact Cenozoic sediments as the top of the K-Pg deposit. Although the formal boundary between the Cretaceous and the Paleogene is at the base of all impact-related deposits [Molina et al, 2006] that depth within the crater is difficult to determine precisely, and thus following the Schulte et al [2012] discussion of a proximal impact sequence in Mexico, we refer to the entire thickness of impact deposits below the post-impact Paleogene sediments as the K-Pg event deposit. Additionally, in ICDP drillsite Yax-1 located close to the crater rim but within the terrace zone ( Figure 2), Whalen et al [2013] observed significant sediment deformation structures for~100 m above the top of the K-Pg event deposit which lies at~795 m. These sedimentary structures above the K-Pg deposits in the core data suggest that sediment deformation was common and then episodic during the early Paleogene history within the terrace zone [Whalen et al, 2013].…”

The Weathering-Modified Iridium Record of a New Cretaceous—Palaeogene Site at Lechówka Near Chełm, SE Poland, and Its Palaeobiologic Implications

“…Walliser 1984), it is generally easy to identify the K-Pg boundary in distal ma− rine successions, because it represents a sudden collapse of carbonate production, characterised by a thin ejecta−rich dark clay horizon (up to 10 cm thick; e.g., Smit 1999;Claeys et al 2002;Molina et al 2009;Schulte et al 2010). The strati− graphic continuity of many K-Pg successions is question− able (e.g., MacLeod 1995), and, therefore, correlation by im− pact evidence offers a specific chronostratigraphic tool (see Molina et al 2009).…”

“…Walliser 1984), it is generally easy to identify the K-Pg boundary in distal ma− rine successions, because it represents a sudden collapse of carbonate production, characterised by a thin ejecta−rich dark clay horizon (up to 10 cm thick; e.g., Smit 1999;Claeys et al 2002;Molina et al 2009;Schulte et al 2010). The strati− graphic continuity of many K-Pg successions is question− able (e.g., MacLeod 1995), and, therefore, correlation by im− pact evidence offers a specific chronostratigraphic tool (see Molina et al 2009). The preserved sedimentary record of a geologically instantaneous event, corresponding to the syn− chronous fallout of impact−related material that persisted at most several months for the finest, sub−micrometre iridium− rich stratospheric dust (Toon et al 1997; see also Kring 2007), is the best available proof of continuous record and eliminates the frequent ambiguity of biostratigraphic dating.…”

Fossil Worm Burrows Reveal Very Early Terrestrial Animal Activity and Shed Light on Trophic Resources after the End-Cretaceous Mass Extinction

“…At these sites, latest Cretaceous strata are overlain by a relatively thin (<3 cm) [3], [4] boundary claystone with physical and chemical features indicative of impact ejecta [5]–[8]. The base of this layer is defined as the K/Pg boundary [9]. Analyses of faunal recovery in the earliest Paleocene often focus on vertebrate radiations, but it is difficult to reconstruct ecosystem structure during this interval.…”