Terra Nova, 24, 333–338, 2012
A widespread marine transgression, which began at the very end of the Early Aptian, is well recorded in Mexico and Spain. In Mexico, this transgression was the most important Aptian transgressive event and its record begins in the Dufrenoyia justinae Zone, whereas in Spain the corresponding transgression is registered in the uppermost part of the Dufrenoyia furcata Zone. The basal age of this Tethyan transgression does not correspond exactly to any of the Lower Aptian third-order sequences as reported in the literature. In Spain, the most important Aptian transgressive event was earlier, corresponding to the Tethyan sequence Ap3, which is well-defined below this transgression reported herein. Consequently, it is possible to correlate this later transgressive event with the third-order Ap4 sequence, which has commonly been attributed to the Upper Aptian. The available ammonoid data allow us to correct the basal age of the transgression, and to correlate the start of the ammonite record in Mexico with the Tethyan sequence Ap4.