Onshore–offshore correlation of the Llobregat deltaic system, Spain: Development of deltaic geometries under different relative sea-level and growth fault influences

Groundwater resources in deltaic aquifers are essential in the Mediterranean region to sustain the socio-economic development of coastal communities and shallow-water ecosystems. Understanding the geological connection between coastal aquifers and the offshore sedimentary record is important to better predict consequences in terms of water management. In spite of this, most approaches to Postglacial and Pleistocene deltaic sedimentation focus either on the offshore or the delta plain; few studies correlate and integrate the entire system. In the Llobregat delta (south of Barcelona, Spain), onshore–offshore correlation is achieved by integrating data from sediment cores acquired on the deltaic plain with seismic profiles from offshore. Data integration enables the reconstruction of the entire deltaic system, providing a more well-defined picture and a better understanding of the onshore–offshore stratigraphic framework in a Late Quaternary, tectonically active narrow shelf in the western Mediterranean Basin.The late Quaternary record in the Llobregat delta shows an unusual well preserved transgressive–regressive cyclic stacking pattern, which displays peculiarities compared with most Mediterranean Quaternary deltaic shelves given that the transgressive and highstand intervals appear to be significantly preserved both onshore and offshore. The preservation of these deposits is attributed to the high subsidence rate on the continental margin controlled by Quaternary faults and the structure of the basement, and by sediment supply fluctuations. Depositional sequences also reveal contrasting patterns between the northeastern and southwestern Llobregat shelves, and show significant variability in the dip direction. The results are compared with diverse stratigraphic architectures reported elsewhere, and provide information to the ancient delta deposits about the distinct types of deltaic geometries generated under different sea-level trends, helping to improve sequence stratigraphic models, where deltaic geometries generated during specific intervals of the sea-level curve are poorly constrained and/or documented.