Oriented Drill Cores

Tobias Stephan

2025-11-01

This vignette describes how convert alpha-beta (and gamma) measurements from oriented drill cores into geological planes and lines using the drillcore_transformation() function of the {structr} package.

library(structr)

The function drillcore_transformation() calculates the orientation of a plane or line from internal core angles (α, β, and γ) of oriented drill cores.

azi is the azimuth of drill core axis orientation (in degrees, measured clockwise from North), and inc is the inclination of drill core axis (in degrees).

azi <- 225
inc <- 45

Note that negative values for the inclination indicate downward direction

alpha and beta are the internal core angles alpha and beta, respectively, measured in degrees.

drillcore_transformation(azi, inc, alpha = 60, beta = 320)
#> Plane object (n = 1):
#> dip_direction           dip 
#>      25.00392      70.02959

The function returns a spherical objects. Since only alpha and beta angles are specified, the output is a "plane" object.

For several alpha and beta angles:

planes_AB <- drillcore_transformation(azi, inc, alpha = c(60, 45), beta = c(320, 220))

The orientations can be plotted in a equal-area (lower hemisphere) projection:

# initialize plot:
stereoplot()

# plot the core axis' azimuth and inclination)
stereo_point(Line(azi, inc), lab = "core-axis")

# plot the plane orientations as poles...
stereo_point(planes_AB, lab = c("A", "B"), col = c("#B63679FF", "#FB8861FF"))

# ... and as great circles
stereo_greatcircle(planes_AB, col = c("#B63679FF", "#FB8861FF"))