ABSTRACT: Graphic correlation shows that the sediment record is incomplete in most sections that embrace the Cenomanian/Turonian transition of the Guerrero-Morelos platform. Three Tethyan zones span the Cenomanian/Turonian interval in the Guerrero- Morelos platform. One unconformity is near the base of the Middle-Upper Cenomanian Pseudorhapydionina dubia Zone and several are in the Upper Cenomanian-Lower Turonian Whiteinella archaeocretacea Zone. Continuous deposition resumed at the base of the Lower Turonian Helvetoglobotruncana helvetica Zone. The drowning unconformity of the platform is at the contact between the Morelos and Cuautla or Mexcala formations and is dated as latest Cenomanian. The base of the Turonian at 93.50 Ma is at or a few meters above this disconformable contact in most sections, so drowning began before the end of the Cenomanian by a minimum of 600kyr where the top of the Morelos is not eroded.
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