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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...

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Problems with measuring fault slip in the subsurface can sometimes be overcome by using subsurface structural contour maps constructed from well logs and seismic information. These maps are useful for estimating fault slip since fault motion commonly causes the dislocation of structural contours. The dislocation of a contour is defined here as the distance in the direction of fault strike between two contours which have the same value on both sides of a fault. This dislocation can be estimated for tilted beds and folded beds as follows: If a dip‐slip fault offsets a tilted bed, the dislocation (Sc) of contours can be estimated from the vertical component (Sv) of the fault slip and the dip (β) of the bedding according to the following relationship: Sc= Sv/tan β. Since Sc and β can be measured from a contour map, the vertical component of fault slip can be obtained from this equation.If a strike‐slip fault offsets a tilted bed, the dislocation (Scs) of contours is equal to the strike‐slip of the fault (Sc), that is, Scs= Ss. If a fault offsets a symmetric fold, the strike component (Scs) of fault slip and the dislocation of the contours (Sc) can be calculated, respectively, from the equations Scs= (Smax+ Smin) / 2 and Sc= (Smax ‐ Smin) / 2. Smax is the greater total dislocation (Sc+ Scs) of a contour line between the two limbs of the fold and Smin is the smaller total dislocation (Sc ‐ Scs) for the same contour line. In this case, Sv can be also calculated using the obtained value of Sc and the equation Sv= Sc tan β. Similarly, for an asymmetric fold, the dislocation of contours due to the vertical slip component is Scb= (Smax ‐ Smin)/(n + 1), and the strike‐slip component is Ss= Scs= (nSmin+ Smax/(n + 1), where n is the ratio between the values of interlines of the two limbs, and Scb is the dislocation of contours due to the vertical slip component for either of the two limbs (here it is for limb b). In all cases, three conditions are required for the calculation of contour dislocation: the contour lines must be approximately perpendicular to the fault strike; the intersection angle between the fault strike and the strike of bedding should be greater than 65°; the bed must not be dip more than 35°; and folding or flexure of the stratigraphic horizons must have occurred before faulting. These methods for determining fault slip from the dislocation of structural contours are discussed using case studies from the Cantarell oilfield complex, Campeche Sound (southern Gulf of Mexico), the Jordan‐Penwell Ellenburger oilfield in Texas, and the Wilmington oilfield in California.

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