Description: The term ldquomud volcano systemrdquo is coined to describe the set of structures associated with a constructional edifice (mud volcano) and feeder complex that connects the volcano to its source stratigraphic unit. Three-dimensional (3-D) seismic data from the South Caspian Basin are used to investigate the structural elements and evolution of these systems. Mud volcano systems initiate via early, kilometer-scale, biconic edifices termed ldquopioneerrdquo cones. These are fed by fluidization pipes tens of meters in width. Subsequent kilometer-scale mud volcanoes grew via persistent extrusion, fed by numerous additional fluidization pipes injected in the country rock. This subvolcanic intrusion complex creates a densely intruded, cylindrical zone, similar in cross section to gryphon swarms observed at an outcrop onshore. Wall rock erosion and compaction of the intruded zone leads to the collapse of a downward-tapering cone enveloping the cylindrical zone, capped by ring faults that define a kilometer-scale caldera that downthrows the overlying mud volcano. Mud volcanoes get buried during basin subsidence and can look like intrusive laccoliths at first glance on seismic data. Reactivation of mud flow through a conduit system generates a stack of superimposed mud volcanoes through time. Large volcanoes continue to dewater during burial and may locally remobilize. This model of mud volcano evolution has similarities with igneous and salt tectonic systems. To reduce drilling and geologic uncertainty, mud volcano system extent and impacts on a reservoir can be assessed on 3-D seismic data.

Description: Three-dimensional seismic-reflection data are used in the analysis of submarine channel systems in the Espírito Santo Basin, Brazil. The exceptional quality of the studied data set allows the detailed documentation of the geometry, regional distribution, and statistical parameters of salt-related normal faults, and their effect on the Rio Doce Canyon system (RDCS). On the Espírito Santo continental slope, normal faulting was triggered during early halokinesis (stage A] but barely controlled the initial evolution of the RDCS, which incised the continental slope axially within a salt-withdrawal basin. However, in a second stage (stage B), crestal or radial faults controlled erosion over growing salt structures, whereas synclinal and channel-margin fault sets dissected overbank strata to the RDCS. In the later part of stage B, channel sinuosity decreased sharply in response to fault activity and associated sea-floor desta-bilization. Vertical propagation of blind faults was triggered in a third stage (stage C), in association with crestal collapse of buried salt anticlines and regional diapirism, but synclinal and channel-margin faults did not propagate vertically above a regional unconformity marking the base of stage C strata. Statistical analyses of observed fault sets demonstrate that synclinal faults are in average 2.3 times longer than the crestal or radial types but record 60% of the throw (average 83 m [272 ft]] experienced by the latter. In addition, the fault sets are shown to have contributed to local cannibalization of the sea floor, vertical stacking of channel-fill strata, and structural and deposi-tional compartmentalization of potential reservoir successions. As a result, channel systems show marked differences in mean values for sinuosity, height, and width in relation to five main phases of channel development. The structural setting in the study area differs from productive areas offshore Espirito Santo (e.g., Golfinho field), west Africa, and Gulf of Mexico, revealing in distal parts of the Brazilian margin the existence of local controls on submarine channel architecture and structural compartmentalization prior to the main stages of diapirism.