| Description |
Clastic pipes are cylindrical injectites that vertically crosscut sedimentary bedding with sharp contacts. Detailed examination of outcrops in the Jurassic Carmel Formation in southern Utah reveals thousands of pipes. Pipes form via fluidization and were likely triggered by an earthquake due to reactivation of a basement-cored uplift. Modern analogs, laboratory models, and comparative outcrop examples reveal the different fluidization morphologies between water versus gas escape. Gas escape structures form positive relief sand volcanoes, and taper to a point in the subsurface. Water escape structures also form cone-shaped extrusion features; but are connected to columnar pipes. Pipe formation produces distinct spatial patterns across multiple scales indicating a set of nested controlling factors on fluidization processes. Pipes occur in a broad band from the Arizona/Utah border to Moab, Utah in sabkha and wet eolian sediments parallel to the Middle Jurassic Sundance Sea, demonstrating the facies control of water-saturated, porous sediments on pipe formation at the basin-scale. Spatial patterns of pipes on m to 100s of m scales reveal that pipes form in self-organized, evenly spaced arrangements. Statistical methods and a laboratory physical model confirm that the size of the pipe spacing scales with the diameter of the pipe. Once emplaced, clastic pipes act as diagenetic flow conduits. Field and laboratory methods reveal multiple iron oxide, clay, and carbonate phases. Initial host rock cements iv formed within 2 Ma of deposition. Later, carbonate, iron oxide and clay minerals phases were precipitated during burial and uplift. Hydrocarbons moved through the pipes during early, burial, and uplift diagenesis, indicating that the Carmel Formation pipes acted as migration pathways. Recent Martian imagery reveals that pipes occur across multiple scales, terrains, and time periods. Similar to terrestrial pipes, these cylindrical Martian features form self-organized, evenly spaced spatial patterns. The pipes are internally massive with raised rims. Pipes require a near-surface, saturated zone of sediment (i.e. groundwater) to form, implying that Mars had a groundwater system. Overall, these studies of clastic pipes comprise an important baseline framework for understanding the relevance of pipes as: environmental indicators; flow conduits; diagenetic archives; and signals for the presence of groundwater on Mars. |
