The question asks for features that strongly suggest the presence of a faultline scarp, even without directly observing the fault plane.

Identifying Presumptive Faultline Scarps

A faultline scarp is a step-like landform created by fault movement. Several geological features can indicate its presence. We need to identify the *most* presumptive indicator among the options.

Analysis of Options

• Superimposed drainage across a fault: This is a key indicator. When a river or stream established on older rock layers continues to flow across younger structures (like a fault scarp) after uplift and erosion, its pattern can reveal the underlying geology. If the drainage maintains its course across the scarp, it implies the scarp is a distinct geomorphic feature related to the fault, acting as presumptive evidence for the scarp's existence and relative youth.
• Poor correlation between rock resistance and topographic forms: While tectonic activity like faulting can disrupt normal relationships between rock type and landforms, this is often a less direct or less visually obvious indicator compared to drainage patterns.
• Frequent severe earthquakes: Earthquakes are evidence of fault *activity*, but they don't directly identify the specific landform of a faultline scarp. A fault might be active without producing a prominent scarp, or a scarp might exist from past activity without current frequent quakes.
• Actual Fault Plane identified along a scarp: Identifying the fault plane itself is definitive proof of a fault, not presumptive evidence *for* a scarp. The question asks for indicators that *presume* the scarp's presence.

Conclusion

Superimposed drainage is considered a strong presumptive indicator because the drainage pattern reflects the erosional history and topographic evolution, and its interaction with the fault scarp directly highlights the scarp as a significant landform.

Therefore, superimposed drainage across a fault is a strongly presumptive sign of a faultline scarp.