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/