# Relationship history for MSHA mine 0503143

Current hierarchy: **Unocal Corp → Union Oil Company Of California → Parachute Creek Long Ridge**

- 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

- **operator_operates_mine:** Union Oil Company Of California → Parachute Creek Long Ridge; 1978-03-09 to current/open; source msha-controller-operator-history
- **controller_controls_mine:** Unocal Corp → Parachute Creek Long Ridge; 1978-03-09 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** Unocal Corp → Union Oil Company Of California; 1978-03-09 to current/open; source msha-controller-operator-history