7. Conclusions  

Schulte et al. conclude that Keller et al. [1] "have not made any case for Chicxulub as a pre-K-T impact." But they made their case by repeatedly resorting to factual misrepresentations, misinterpretations, out of context quotes, selective use of references, ignoring critical studies and bogus arguments. Amazingly, this was done in the most strident tone{1} and accusations of misuse of biostratigraphy, geochemistry, mineralogy and sequence stratigraphy. In our reply we have addressed the major issues they raised and provided new data that show the biostratigraphy and mass extinction relative to the Chicxulub impact layer in the Cottonmouth Creek (CMA-B) and Brazos-1 sections and the nature and origin of the yellow clay and spherules of the event deposit. Our detailed multi- disciplinary research results from the Brazos area stand as verifiable body of work and remain factually unchallenged by Schulte et al.'s arguments. The physical and stratigraphic separation, the detailed geochemical, mineralogical and paleontological analyses presented reveal a historical sequence of events that places the Chicxulub impact unequivocally in the late Maastrichtian prior to the K-T mass extinction. The event deposit, where Schulte et al. place the K-T boundary based on reworked impact spherules, is no more than an incised valley filled with eroded sediments during a low sea level. The mass extinction occurred at a considerably later time during a sea level rise and is marked by the global d13C shift.

2} The physical and stratigraphic separation of the Chicxulub impact spherules and iridium anomaly are a red herring from mother Nature, who placed a trap in the Gulf of Mexico KT deposits for the naive and unawares among us.
Keller et al2007/2008 fell into that trap, by declaring this "separation of 300kyr" a holy fact. This "fact" was first mentioned, I believe in a paper by Keller et al in 2002? (see below). This notion attracted immediate criticism, but Keller chose to defend stubbornly this 300kyr separation ever since, although all the defenses are relatively easily countered. Once you have made up your mind, it is very difficult to retreat a once taken standpoint.

The iridium anomaly and the impact spherules from Chicxulub are separated by one complex, but coherent overall graded clastic unit with the iridium anomaly already in the top of it. Recent papers by Keller are intended to show that the Chicxulub impact occurred even considerably below the clastic event and spherule beds, although the Chicxulub impact certainly triggered currents and tsunamis in the Gulf, that can easily explain these clastic beds. Also here mother Nature plays her tricks. The "layers" of spherules 4-6 m below the event beds, are actually pockets of spherules sunk deeply into the soft seafloor as giant ball and pillow structures. Layers would be continuous, but if one investigates the outcrops closely, none of these co-called layers has any continuity, they simply stop a little distance laterally.