Use this geological calculation for a transparent first-pass interpretation of measured rock, soil, fluid, well, stratigraphic, isotopic, geophysical, or seismic data under an explicitly selected model.

Overlying dip

Dip of strata above the unconformity in degrees.

Underlying dip

Dip of strata below the unconformity in degrees.

Angular discordance across an unconformity: the absolute difference between dip of beds above and dip of beds below, assuming comparable dip directions. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Discordance

Angular discordance across the unconformity in degrees.

• Apparent dip, thickness, fault, and fold geometry depend on coordinate convention, orientation measurements, map or section geometry, exposure, projection, and assumptions about planar or cylindrical structures. Ambiguous contacts require field or 3D validation.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Compare independent measurements and models, retain units and analytical metadata, propagate uncertainty, and validate interpretations against logs, cores, maps, laboratory data, or field observations.

• Downlap Angle Calculator

  Angle between downsloping (progradational) strata and the older surface onto which they downlap: |dip(strata) - dip(basal surface)|, assuming comparable dip directions.

• Onlap Angle Calculator

  Angle between dipping strata and the inclined older surface they progressively onlap: |dip(strata) - dip(substrate)|, assuming comparable dip directions.

• Toplap Angle Calculator

  Angle between initially inclined strata and the nearly horizontal upper surface beneath which they toplap: |dip(strata) - dip(upper surface)|, assuming comparable dip directions.