How complete are Cretaceous/Tertiary boundary sections? A chronostratigraphic estimate based on graphic correlation

We have employed the graphic correlation technique to summarize biostratigraphic and lithostratigraphic data from 15 intensively sampled K/T boundary sections within a common chronostratigraphic model. Our results indicate that almost all of these sections, along with 13 additional boundary sections not used to construct the model, contain prolonged and in many cases multiple hiatuses. Of these 28 boundary sections, only six were found to contain a continuous record of sediment accumulation across the K/T boundary itself. These six K/T-complete sections are El Kef (Tunisia), Agost (Spain), Caravaca (Spain), and three sections along the Brazos River (Texas). A comparative analysis of hiatus distributions among these 28 K/T boundary sections also reveals the presence of systematic differences between continental-shelf and deep-sea depositional environments. Our data suggest that the apparently sudden mass extinction of planktonic Foraminifera and anomalies in the occurrence of geochemical tracers that are characteristic of the K/T boundary in deep-sea sections may be artifacts of a temporally incomplete deep-sea stratigraphic record. -from Authors