Early diagenetic isotopic signal at the Cretaceous/Tertiary boundary, Israel

Carbon and oxygen isotope records from carbonate fractions in marls overlying the K/T boundary in southern Israel are used to interpret paleoenvironmental changes and the history of early diagenetic events in the earliest Tertiary. The delta super(13)C record of the whole rock does not significantly depart from the original values and reflects the global productivity drop shortly after the K/T boundary and the subsequent recovery. Fine fraction oxygen isotope values reflect the addition of carbonate cement highly depleted in super(18)O throughout the profile. The delta super(18)O record demonstrates two main episodes in which contact with fresh water affected the sediments. One is below a short hiatus at planktic foraminiferal subzone transition PO/Pla (Guembelitria cretacea/Parvularugoglobigerina eugubina) and the other at an pyrite- rich clay layer near the top of planktic foraminiferal subzone Plb ('Globigerina' taurica). The latter event suggests introduction of sapropelic bottom conditions in the oceanic paleoenvironment. (DBO)