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An observed contact must identify a genuine intrusion or fault displacement before cross-cutting relationships establish event order. The intrusion or fault event postdates the rock unit it physically cuts. In the USGS illustrated granite-dike example, baked margins support interpreting the contact as intrusive. These relationships establish relative order, without numerical ages or elapsed time. Analyst deductions from the local observational scope: order only event comparisons supported by observed relationships; unrelated units may remain unordered, and absence of observed cutting alone establishes no chronology.

Primary sources:
- https://pubs.usgs.gov/gip/fossils/laws.html
- https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/glad-you-asked-how-do-geologists-know-how-old-a-rock-is/

Cross-cutting relationships establish qualified event order

Identified pre-existing rock fragments incorporated into an igneous or coarse sedimentary host predate their incorporation into that host. The comparison concerns the fragments' prior existence and the host incorporation or formation event. This relationship supplies relative order, without numerical ages or duration. Limit the rule to these pre-existing rock fragments; it does not establish that every mineral grain or later feature inside a rock predates its host. Analyst deduction from the local observational scope: observing separate fragments in one host alone does not establish their order relative to one another.

Primary sources:
- https://geology.utah.gov/map-pub/survey-notes/glad-you-asked/glad-you-asked-how-do-geologists-know-how-old-a-rock-is/

Pre-existing rock inclusions precede incorporation into their host

The study of non-living systems that covers fields such as physics, chemistry, earth science, etc.

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