Stable-isotope stratigraphy of the Cenomanian-Turonian (Upper Cretaceous) boundary event (CTBE) in Wadi Qena, Eastern Desert, Egypt

作者：Nagm Emad^*; El Qot Gamal; Wilmsen Markus

来源：Journal of African Earth Sciences, 2014, 100: 524-531.

DOI：10.1016/j.jafrearsci.2014.07.023

• Cenomanian-Turonian
• CTBE
• Chemostratigraphy
• Eastern Desert
• Egypt

A high-resolution delta C-13 isotope record from Cenomanian-Turonian boundary interval of shallow marine successions in Egypt is presented. The delta C-13 curves show the typical features of the globally documented Cenomanian-Turonian positive excursion, including three of the main positive isotope peaks defining the Cenomanian-Turonian Boundary Event (CTBE). Based on high-resolution ammonite biostratigraphy, the CTBE started in the study area above the Late Cenomanian Neolobites vibrayeanus Zone within the Galala Formation, directly above the global sequence boundary Cenomanian 5 (SB Ce 5). A stratigraphic gap at that level cuts out the lower a-peak of the CTBE. The Cenomanian-Turonian boundary is located within the upper part of the positive excursion between carbon excursion peaks c and d, coinciding with the boundary between the Late Cenomanian Vascoceras cauvini and the Early Turonian Vascoceratid zones. The CTBE ended up-section of peak d, at the base of the Choffaticeras spp. Zone. The amplitude of the positive delta C-13 excursion in Egypt is very high (reaching 6.5 parts per thousand vs. V-PDB) and largely matches curves of European standard sections and others localities from different basins. Furthermore, the Lower Turonian Holywell Isotope Event, an important marker within the lowermost Turonian, has tentatively been recognized. The positive carbon stable isotope curves presented herein represent the outreach of the oceanic anoxic event (OAE) 2 in shallow-water nearshore sequences.

• 出版日期2014-12