Abstract. When interpreting geophysical models, we need to establish a link between
the models' physical parameters and geological units. To define these
connections, it is crucial to consider and compare geophysical models with
multiple, independent parameters. Particularly in complex geological
scenarios, such as the rifted passive margin offshore Namibia,
multi-parameter analysis and joint inversion are key techniques for
comprehensive geological inferences. The models resulting from joint
inversion enable the definition of specific parameter combinations, which
can then be ascribed to geological units. Here we perform a user-unbiased
clustering analysis of the two parameters electrical resistivity and density
from two models derived in a joint inversion along the Namibian passive
margin. We link the resulting parameter combinations to breakup-related
lithology and infer the history of margin formation. This analysis enables
us to clearly differentiate two types of sediment cover. The first type of
sediment cover occurs near the shore and consists of thick, clastic sediments,
while the second type of sediment cover occurs further offshore and consists
of more biogenic, marine sediments. Furthermore, we clearly identify areas
of interlayered massive, and weathered volcanic flows, which are usually
only identified in reflection seismic studies as seaward-dipping reflectors.
Lastly, we find a distinct difference in the signature of the transitional
crust south of and along the supposed hotspot track Walvis Ridge. We
ascribe this contrast to an increase in magmatic activity above the volcanic
centre along Walvis Ridge and potentially a change in the melt sources or
depth of melting. This change of the predominant volcanic signature
characterizes a rift-related southern complex and a plume-driven Walvis
Ridge regime. All of these observations demonstrate the importance of
multi-parameter geophysical analysis for large-scale geological
interpretations. Additionally, our results may improve future joint
inversions using direct parameter coupling, by providing a guideline for the
complex passive margin's parameter correlations.