Sequence stratigraphy framework of the Cretaceous mixed carbonate-siliciclastic rocks in the northeast part of Oriente Basin

The Cretaceous consists a series of carbonate-siliciclastic rocks in the northeast part of Oriente Basin. Due to the complex structural and lithologic traps discovered, it is the key step for the further exploration to... [ view full abstract ]

The Cretaceous consists a series of carbonate-siliciclastic rocks in the northeast part of Oriente Basin. Due to the complex structural and lithologic traps discovered, it is the key step for the further exploration to establish the accurate architecture of sequence stratigraphy and sedimentary facies. Based on core, well logging and seismic data, sequence stratigraphic framework of the Cretaceous was established by identifying seismic terminations, sudden lithologic changes and variation in the stacking patterns of the parasequence in the lithology and well logging sections. The Cretaceous as a 2nd-order sequence was divided into 6 3rd-order sequences, 16 4th-order sequences and 34 5th-order sequences. Limestone layers in different sequence played significant roles in recognizing the first and the maximum flooding surfaces. According to the paleogeography and lithology, Createous developed a typical mixed carbonate-siliciclastic gentle slope model with type II sequence bounary in the northeast Oriente Basin. The third-order sequences were composed of SMST, TST and HST. The cycles of the third-order sequences exhibited a regular variation pattern and went through distinct transgression-regression cycles. Cretaceous deposited in a laterally extensive and gentle slope where seaward successively distributed low-energy estuary, wide tidal flat, restricted platform (subaqueous lagoon), submerged shoals and open sea shelf based on facies markers from cores, lithologic section, well logging facies and seismic facies. The Cretaceous mixed carbonate-siliciclastic architecture of sequence stratigraphy and sedimentary facies were controlled by tectonic evolution, relative sea-level change, sediment supply rate and climate etc. It is significant for mixed carbonate-siliciclastic sequence to establish the isochronous sequence stratigraphy framework, especially to define the first flooding surface and the maximum flooding surface using the limestone layers for the first try. Results and achievements in this study will provide scientific foundation for further seeking favorable sandstone and subtle traps of the Cretaceous in the northeast part of Oriente Basin.