Preservation of Last Interglacial and Holocene transgressive systems tracts in the Netherlands and its applicability as a North Sea Basin reservoir analogue

Abstract

Understanding of complex sedimentary records formed by transgressive systems is critical for hydrocarbon exploration and exploitation, and carbon capture and storage. This paper discusses the facies proportions and preservation of the Last Interglacial and Holocene transgressive systems tracts in the Netherlands and their applicability as a North Sea Basin analogue for the Early Jurassic Åre Formation in the Norwegian offshore. New and existing data from both (sub-)modern transgressive Rhine records were thoroughly reviewed from a sequence stratigraphic perspective, before volumetrics were calculated and longitudinal trends quantified at reservoir scale. Large differences between the Last Interglacial and Holocene transgressive systems were found: the volume of fluvial deposits is almost six times larger and the volume of organics nearly twenty times larger in the Holocene record than in the Last Interglacial record. In contrast, the volume of estuarine deposits in the Holocene record is only half of that of the Last Interglacial record. Remarkably, both records show similar averaged sediment-trapping rates of 8–9 km3/ka. Initial valley configuration and relative sea-level rise-rates during both transgressions were key controls on the volume and spatial arrangement of the transgressive deposits. Relative sea-level fall and river avulsion determined what amount of sediment was left preserved after completion of one interglacial-glacial cycle. Comparison of the Late Quaternary Rhine records with the Late Triassic to Early Jurassic Åre Formation in the Heidrun Field off mid-Norway, showed the potential of the (sub-)modern Rhine records as analogues for ancient stratigraphic records. Especially the transgressive Rhine sequence from the Last Interglacial provided remarkable similarities in facies proportions, preservability, autogenic processes and controlling forcings, ranging from metre-scale vertical-successions to kilometre-scale field-wide events for parts of the Åre Formation. The side-by-side availability of the truncated Last Interglacial and (still) fully preserved Holocene transgressive system proved to be an excellent natural laboratory to study the stratigraphic architecture and assess depositional trends and preservability over longer time scales (>100 ka). It nevertheless demonstrates that no ‘one-size-fits-all’ analogue exists, but that various other analogues are needed to solve the complex puzzle which the Åre Formation resembles.