# Relationship history for MSHA mine 4607931

Current hierarchy: **Occidental Petroleum Corp → Island Creek Coal Company → Rockhouse #1**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-17T05:35:58.500035+00:00

## Valid-time edges

- **controller_controls_mine:** Occidental Petroleum Corp → Rockhouse #1; 1950-01-01 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Sharon  Preece et al → Rockhouse #1; 1990-07-27 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** Island Creek Coal Company → Rockhouse #1; 1990-09-01 to 1991-04-15; source msha-controller-operator-history
- **controller_controls_operator:** Occidental Petroleum Corp → Island Creek Coal Company; 1990-09-01 to 1991-04-15; source msha-controller-operator-history
- **operator_operates_mine:** Ray Todd Coal Company Inc → Rockhouse #1; 1991-04-16 to 1992-06-21; source msha-controller-operator-history
- **controller_controls_operator:** Sharon  Preece et al → Ray Todd Coal Company Inc; 1991-04-16 to 1992-06-21; source msha-controller-operator-history
- **operator_operates_mine:** Island Creek Coal Company → Rockhouse #1; 1992-06-22 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Occidental Petroleum Corp → Island Creek Coal Company; 1992-06-22 to current/open; source msha-controller-operator-history