spec: add column-stratigraphic specification

[github-actions]

New Specification: column-stratigraphic

Related to #4573

---

specification.md

column-stratigraphic: Stratigraphic Column with Lithology Patterns

Description

A vertical column visualization showing geological rock layers with standardized lithology patterns, formation names, ages, and thickness scales. Each layer is represented as a stacked rectangular block filled with a distinctive pattern (e.g., brick pattern for limestone, dots for sandstone, dashes for shale) following FGDC/USGS conventions. This plot is essential for communicating subsurface geology and sedimentary sequences in a compact, standardized format.

Applications

• Stratigraphy: describing borehole or outcrop sections with standardized lithology symbols for geological reports
• Petroleum geology: visualizing well log lithological intervals alongside wireline log data
• Environmental geology: site characterization showing subsurface material types and aquifer geometry
• Geological education: teaching sedimentary sequences, unconformities, and stratigraphic principles

Data

• top (numeric) - depth or elevation of the top of each layer in meters
• bottom (numeric) - depth or elevation of the bottom of each layer in meters
• lithology (categorical) - rock type for each layer (e.g., sandstone, limestone, shale, siltstone, conglomerate)
• formation (string) - formation or member name for each layer
• age (string) - geological age label (e.g., "Cretaceous", "65 Ma")
• Size: 5-20 layers
• Example: a synthetic sedimentary section with 8-10 layers of varying thickness and lithology, spanning multiple geological periods

Notes

• Each lithology type should use a distinct fill pattern (hatching or texture) that approximates standard geological map symbols (e.g., brick pattern for limestone, stipple dots for sandstone, horizontal dashes for shale, random dashes for siltstone)
• The vertical axis represents depth or thickness (increasing downward by convention in borehole logs, or upward for outcrop sections); use increasing downward for this spec
• Formation names should be labeled to the right of or within each layer
• Age labels or geological period names should appear on the left side or as annotations
• A thickness/depth scale bar should be shown on the left axis with appropriate units (meters)
• Layer boundaries should be drawn as solid horizontal lines; unconformities may use wavy lines
• Use a minimum of 5 distinct lithology patterns to demonstrate variety

---

Next: Add approved label to the issue to merge this PR.

---

🤖 spec-create workflow