Detection, quantification, and significance of hiatuses in pelagic and hemipelagic strata

Temporal gaps in the stratigraphic record have important implications for the interpretation of stratigraphically rapid geochemical and paleobiologic changes, for the development of high-resolution time scales (e.g., orbital time scales), and for deciphering the response of depositional systems to climatic change and basin evolution (e.g., accommodation space vs. sediment supply). In ancient pelagic and hemipelagic strata, the identification of relatively short hiatus (10(3)-10(6) years) is commonly challenged by the resolution limits of geochronologic techniques. In this study, a quantitative method is developed to identify and quantify hiatuses in strata where Milankovitch orbital cycles are documented. The new method is based on the interpretation of evolutive harmonic analysis (EHA) results and permits estimation of minimum durations for the temporal gaps. Application of this technique to an optical densitometry data series derived from the Cenomanian/Turonian (C/T) Bridge Creek Limestone Member permits quantification of hiatus within the unit and addresses important questions about abrupt changes in biogeochemical proxy records across the boundary interval. Integration of the new method with stratigraphic data and geochemical burial flux estimates permits a detailed reconstruction of the controls on sediment delivery and hiatus generation, including a refined analysis of the orbital-scale linkages between climate and sedimentation. (C) 2004 Elsevier B.V. All rights reserved.