f Multi- Chronological Proxies to Timing Early Oligocene and Middle Miocene Deformation Events Along the Lower Magdalena Basin, NW Colombia

Understanding the timing of deformation of the San Jacinto Belt (SJB) and its relations with the Sinu Belt and Lower Magdalena Valley (LMV) is vital for predicting regional reservoir compositions and timing the occurrence of structural traps. We combine micropaleontological data and U-Pb detrital zircons ages to timing the deposition of stratigraphic units along the SJB and LMV and trace deformation and exhumation of sedimentary sequences. Whereas palynological assemblages from the continental--‐ deltaic Cienaga de Oro Formation suggest a Chattian--‐Burdigalian depositional age, calcareous nannofossils assemblages suggestan Aquitanian--‐Langhian depositional age for the overlying marine Porquera Formation. The presence of reworked Paleocene--‐Eocene planktonic foraminifera and pollen in both formations suggest the Paleocene‐early Oligocene sediments from the SJB being exhumed and deformed between Early Oligocene and Late Oligocene. A second deformation event took place along the SJB during Langhian--‐Tortonian times. This is evidenced by the occurrence of reworked Paleocene--‐ Early Oligocene planktonic foraminifera and Burdigalian--‐Langhian calcareous nannofossils within the Moñitos and the Sincelejo formations. These units also include palynological assemblages and detrital zircon U-Pb ages that suggest a Serravallian--‐ ortonian maximum depositional age. Finally, seismic data suggest the existence of a major regional unconformity separating the middle Miocene Cienaga de Oro and Porquera transitional/marine sedimentaries from the late Miocene-Pliocene transitional/continental sedimentary record of the Moñitos and Sincelejo formations. The new data presented here highlight the importance of using multi- ‐proxy chronological analysis to timing regional deformational events along continental margin basins and understanding its control on the occurrence of contrasting sedimentary environments and reservoirs.