Lithofacies types present a means to characterize subsurface facies from description of the sedimentological inventory. While sedimentary structures and grain size can be assessed in core and outcrop, dimensions and lateral extension are best observed in outcrops on the 10 to 100m-scale. Thus analogs are needed to map lithofacies types in 2D to 3D.
In our study we assess lithofacies types in a Lower Buntsandstein outcrop of the marginal facies in Southern Germany. The outcrop consists of wavy- and cross-bedded, subarkosic sandstones. Lithofacies types were cropping out in 3D and could be characterized macroscopically and with regard to mineral assemblage allowing to unravel the paragenetic sequence. Petrographic results were linked with porosity and permeability measured in plugs representing three spatial directions. Those revealed that flow directions play a subordinate role in the studied deposit, whereas lithofacies types coincide with markedly different petrophysical properties. The wavy-bedded lithofacies exhibited permeability ranges of 10-3 to 100 mD while the cross-bedded lithofacies type hosts permeabilities of 10-1 to 102 mD. ... mehr
Our case study evidences how lithofacies type mapping in outcrop analogs offers an opportunity to construct and assign buildings blocks for fluid flow models that outdo permeability assessments from wireline logs and core descriptions.