The Tumey Giant Injection Complex (TGIC) is a regionally-developed sandstone intrusion complex emplaced into deep-water Kreyenhagen Shale (Eocene) in the San Joaquin Basin, Central California. Detailed geological mapping, stratigraphic reconstruction and outcrop description, supported by structural analysis, allowed the architectural characterisation of the TGIC. The complex is described as two main stratigraphically-constrained intervals: i) a lower interval (250m thick) emplaced into clay-rich mudrock, consisting dominantly of sills with stepped and multi-layered geometry; ii) an upper interval (200m thick) characterized by injection breccia and large wing-like intrusions (ca. 600m width × 100m high) emplaced within predominantly biosiliceous mudrock strata. The intrusions in both intervals were derived from turbiditic channel-fills intensely modified by sand fluidisation. Sandstone intrusions and fractures affecting host strata are dominantly oriented sub-parallel to the basin axis striking between NW-SE and N-S, mainly dipping to NE and forming asymmetric saucer-shaped intrusions, suggesting structurally-driven hydraulic fracturing and sand emplacement. The absence of a deep aquifer and potential sand sources underlying the complex suggests a lateral contribution of fluid flow. The TGIC occurs at a scale similar to injection complexes recognized in the subsurface and is a valuable reservoir analogue for hydrocarbon accumulations associated with sand injectites.
|Name||Geological Society Special Publications|
|Publisher||Geological Society of London|
The authors gratefully acknowledge support from Shell Brazil and CNPq through the “BG05: UoAUFRGS-SWB Sedimentary Systems” project at UFRGS and UoA and the strategic importance of the support given by ANP through the R&D levy regulation. We also wish to thank the support from the Sand Injection Research Group (SIRG) and the researchers who collaborated during fieldwork. We also wish to thank the support and help of the Bureau of Land Management (CA) providing guidance and legal access to the study area.
- giant sand injection complex
- San Joaquin Basin
- intrusion geometry
- intrusion architecture
- injection breccia
- subsurface analogue