Mud Extrusion Research Articles

Identification of Mud Volcano’s Structure using Gravity Satellite and Fault Fracture Density Analysis: Case Study Ciuyah Mud Volcano, Kuningan, West Java

Mud volcanoes, known as mud extrusion phenomenon, is a geological feature that expels suspended fine-grained sedimentary materials and fluids to the surface due to buoyancy and pressure difference. This geological feature is found almost all over the world and formed in compressional tectonic environments, one of which is the Ciuyah Mud Volcano, Kuningan, Indonesia. Previous studies have shown that the appearance of the mud volcano was influenced by tectonic activity that formed a ‘hypothetical’ fault structure as a pathway for mud migration and extrusion to the surface. Integration of geophysical studies using satellite gravity and geology using fault fracture density analysis was conducted to prove the existence of the ‘hypothetical’ fault structure. The results show that the mud volcano site is located in a low to high gravity anomaly pattern associated with significant density contrast differentiation followed by the maximum value of FHD and low-high SVD pattern oriented west southwest - east northeast (WSW - ENE). The gravity anomaly pattern can be associated with the presence of faults. This is reinforced by the fault fracture density map which shows that the mud volcano site is located in a medium to high fracture density zone (weak zone) associated with good permeability conditions below the surface. Thus, the research results have proven the existence of a ‘hypothetical’ fault as the migration and extrusion pathway of Ciuyah Mud Volcano mud that has been studied previously.

Crater formation during the onset of mud volcanism

AbstractThree-dimensional (3-D) seismic imaging was used to reveal >2.5-km-wide and >150-m-deep craters at the basal surface of 64 mud volcanoes out of a suite of 86, offshore Egypt. The craters were infilled soon after they formed by successive mud extrusions that combined to build mud volcanoes, as evidenced by onlap fill geometries of the earliest mud flows. We propose that the craters formed as the earliest manifestation of mud volcano formation. We infer that the energy required to excise in situ clays and sands buried and consolidated to depths over 150 m below the seafloor was provided by the highly vigorous venting of a dominantly gas and water mix during the initial eruption, in which gas column height was the critical factor. This primary phase of mud volcanism is rarely observed, and the findings presented here have significant implications for interpretations of the dynamism during this fundamental stage of mud volcano genesis.

Morpho-sedimentary structure of new mud volcanoes on the Moroccan Atlantic continental margin (Gulf of Cadiz)

Multibeam bathymetry, sub-bottom parametric profiler, multichannel seismic reflection data and sediment cores were used to detail the nature, morpho-sedimentary and internal structure of five newly discovered submarine mud volcanoes (MVs) in the Moroccan margin of the Gulf of Cadiz. The Henriet and Subvent MVs are located at 300–400 m water depth, while Chueca, Demetrio de Armas and Puerto Real MVs are at 1100–1800 m water depth. Two main types of morphologies are identified: regular cone-shaped edifices (Subvent MV) with a pronounced crater (Henriet MV) in the eastern province; and ridge-attached oval-shaped conical edifices (Chueca, Demetrio de Armas and Puerto Real MVs) in the western province. The overall seismic architecture of these MVs is the result of successive events of mud extrusion and outbuilding alternating with periods of dormancy. The Henriet and Subvent MV system is composed of stacked bicones and intrusive complexes, which penetrated upper Miocene-Quaternary sedimentary units rooted in the Gulf of Cadiz wedge. Major phases of mud extrusion and outbuilding took place since the Late Pliocene with re-activation during mid-Pleistocene. Mud breccias interbedded with hemipelagic/contourite sediments were collected for all MVs. Cores attest to recent periods of mud outflows lasting from the Late Pleistocene (180 ky) whereas the end of MV extrusion could date back to historic times (the last 0.6 ky), giving rise to the onset of a new quiescent activity. The most active MV points out to the Subvent MV. These new MVs are formed in response to the extensional and compressional system within the Gibraltar Arc. In the eastern side, MVs are related to extensional faults forming deep sedimentary basins and forcing overpressured fluids to migrate upwards coeval with thick contourite deposits. On the western side, MVs are related to compressional ridges at the front of fold-thrust systems which act, as pathways to deep-seated fluids to ascent to seafloor.

Preliminary geomorphological and hydrographical characterization of a circular structure in the Marche Region (Central Italy) and its possible origin

The study of Google Earth images of an area located in a southern part of the Marche Region in Central Italy, has revealed a circular feature consisting of a ring system of hills and valleys, both concentric with a central elevation. This morphology was also characterized by different colors of vegetation in cultivated land, and by its hydrographic network. Maps and geological data of the Marche Region were investigated, and a morphometric study showed its main rim to be elliptical, with the long axes oriented about SW-NE. Specifically, the main rim is 373 m high on average, with an average diameter of 3.75 km, and an internal area of 10.5 km2. Four possible processes which could have generated this morphology are investigated: impact cratering, hydrographic organization, brachyanticline, and diapirism. A morphological analysis was performed from the shape indices. The hydrographic parameters do not satisfy Hack's law, excluding a hydrographical origin. Likewise, the available geophysical surveys are not in agreement with the origins from an impact crater and a brachyanticline. The presence of mud extrusions in the area suggests some evidence of a clayey diapiric origin of the structure.

Experimental evidence for lava-like mud flows under Martian surface conditions

Large outflow channels on ancient terrains of Mars have been interpreted as the products of catastrophic flood events. The rapid burial of water-rich sediments after such flooding could have led to sedimentary volcanism, in which mixtures of sediment and water (mud) erupt to the surface. Tens of thousands of volcano-like landforms populate the northern lowlands and other local sedimentary depocentres on Mars. However, it is difficult to determine whether the edifices are related to igneous or mud extrusions, partly because the behaviour of extruded mud under Martian surface conditions is poorly constrained. Here we investigate the mechanisms of mud propagation on Mars using experiments performed inside a low-pressure chamber at cold temperatures. We found that low viscosity mud under Martian conditions propagates differently from that on Earth, because of a rapid freezing and the formation of an icy crust. Instead, the experimental mud flows propagate like terrestrial pahoehoe lava flows, with liquid mud spilling from ruptures in the frozen crust, and then refreezing to form a new flow lobe. We suggest that mud volcanism can explain the formation of some lava-like flow morphologies on Mars, and that similar processes may apply to cryovolcanic extrusions on icy bodies in the Solar System.

The genesis of a giant mud canopy by catastrophic failure of a thick evaporite sealing layer

Abstract Three-dimensional seismic imaging and well calibration reveal a large allochthonous mud edifice that is composed of several mud extrusions and covers an area >740 km2 on the outer shelf slope of the Nile Delta. The allochthonous material was sourced from beneath the ∼1-km-thick Messinian evaporites in the Eastern Mediterranean and extruded synchronously as eight large mud volcanoes directly on top of the Messinian evaporites in a catastrophic remobilization event at the end of the Messinian salinity crisis. These large extrusive flows coalesced to form a single edifice with an exceptional volume of ∼292 km3 that is connected to eight widely spaced conduits. We argue that this large mud body represents a new morphological type and scale of mud extrusion. We propose that mud extrusions that coalesce on a surface forming a multi-conduit-fed edifice be referred to as mud canopies, by analogy with salt canopies, with implications for basin reconstruction, paleo–overpressure release events, and fluid migration.

Mud volcanism by repeated roof collapse: 3D architecture and evolution of a mud volcano cluster offshore Nigeria

Abstract Using 3D seismic data, we document the subsurface architecture of a cluster of 3 mud volcanoes located on the upper continental slope offshore Nigeria. In a background of gently dipping stratified sediments, the subsurface of the cluster contains 8 seismic sequences made of one subcircular syncline, 1–3 km in diameter, and adjoining unstratified units. Synclines flatten out upward through intercalation of unstratified concave-up lenses between stratified units and are eventually filled by a convex-up unstratified lens onlapped by background sediments. The lower boundary of each sequence is a 0.5–1.5 km-deep bowl-shaped unconformity across which high-dip strata rest above truncated low-dip series. We interpret each seismic sequence as a mud volcano system (MVS) sourced from a connected region and evolving through episodes of roof collapse. Three are associated with the surface mud volcanoes and another 4 to fossil ones. Mud volcano systems are dynamic features that record the evolution of: 1) the material extruded from one single connected source region (depletion zone) as it grows downwards and stepwise becomes depleted; 2) the basal unconformity, which joins strata originally separated by material evacuated in the remobilization process; by analogy with salt tectonics, we propose to call it a “mud weld”; 3) the conduits; and 4) the successive collapsed roofs of the depletion zone. The evolution of each mud volcano system in this interpretation records progressive growth of the depletion zone by downbuilding, punctuated by episodes of roof collapse and extrusion. The geometry and evolution of this type of MVS can be interpreted in the light of analogue models of magmatic caldera development: in early stages, the thin roof experiences downsagging while remobilized material is extruded through an axial pipe-like conduit; in later stages the thickened roof undergoes piston-like subsidence, and mud extrusion occurs along the peripheral fault.

Morphology and activity of the Helgoland Mud Volcano in the Sorokin Trough, northern Black Sea

Abstract Morphological change and activity of submarine mud volcanoes (MVs) are still poorly understood. In this study, we integrated acoustic subbottom profiles, Autonomous Underwater Vehicle (AUV) high-resolution bathymetric and backscatter data, Remotely Operated Vehicle (ROV) seafloor observations, Bottom Water Temperatures (BWT), and compositions of gas samples collected from three research expeditions, to study the morphology and activity of the Helgoland mud volcano (Helgoland MV) in the Sorokin Trough of the Black Sea. Based on the micro bathymetric and backscatter maps, we conducted a geomorphological analysis which differentiates the Helgoland MV into five regions, which are: the active center, the inner crest, the inner moat, the outer crest, and an outer moat. Special seafloor features, such as gas bubble emissions, mud breccia and mud pools, were observed in different regions by ROV observations. They indicate a heterogeneous distribution of materials and activities at the Helgoland MV. Active mud extrusion from the center was inferred from BWT elevations (up to 1.652 °C) that showed the same orientation as a major fault (NW-SE) at the location. Methane stable carbon isotopes (−58.1∼−63.6‰) and molecular compositions of light hydrocarbons (C1/C2+ = 2836, CH4 = 99.545%, C2H6 = 0.033%, C3H8 = 0.002%, CO2 = 0.417%) suggest a predominance of biogenic hydrocarbons with an admixture of thermogenic gas. Circular faults surrounding the Helgoland MV, as observed in the bathymetric and sub-bottom profiles, are speculated to be formed due to subsidence of the MV caldera and gravity driven sediment movement. A conceptual model is proposed to explain the interrelationship between the seafloor morphology and activity of the Helgoland MV. Combining multidisciplinary data, especially from the application of ROVs and AUVs, broaden the scope in which the activity and morphology of submarine mud volcanoes can be investigated.

Geological and oceanographic controls on seabed fluid escape structures in the northern Zhongjiannan Basin, South China Sea

Mega-pockmarks, which can reach a few kilometers in width and a few hundred meters in depth, and associated fluid escape features in the Northern Zhongjiannan Basin, South China Sea, have received much attention in the recent years, due to their large variety of morphologies and sizes. In this work, an integrated interpretation of detailed multibeam bathymetry, conventional multi-channel seismic reflection and seismic oceanography sections covering the northern Zhongjiannan Basin, South China Sea, are used to image the seafloor morphology, the subsurface geology and the water column, in order to better understand the geological and oceanographic controls on the formation and evolution of the widespread fluid escape features in this region. Regional uplift and volcanism took place in this area near the Palaeogene–Neogene boundary and, during the Neogene–Quaternary post-rift thermal subsidence period, differential subsidence and diapirism deformed the overlying kilometer-scale successions. Mainly after the Miocene, focused flow of fluids originated at depth occurred along gas pipes, polygonal faults, tapered reflectors and faults into the shallow sediments, resulting in intense fluid blowouts and complex fluid escape structures on the seafloor. Our results show that elongated pockmarks, pockmark gullies and gullies in the northern slope are generally controlled by underlying buried channels and gullies. However, pockmark gullies and gullies in the southern slope are controlled by gravity sliding/slumping, along with crescent pockmarks developing parallel to water depth contours. To varying degrees, intense fluid escape activities associated with mud diapirism and gas escape in the study area resulted in mud extrusion and the formation of mud volcanoes, complex seabed morphologies and irregular pockmarks. Mega-pockmarks, collapse structures and blind valleys have formed at the apexes of tectonic uplifts related to volcanism and above basement highs, which suggests that these processes played a role in creating pathways for fluid escape. Bottom currents associated with the South China Sea Western Boundary Current, imaged here for the first time with the seismic oceanographic method, mainly flow to the south, and erode the seafloor, making pockmark walls and slopes of gullies and channels in the north steeper than those in the south. Some fluid escape structures, such as the mega-pockmarks and pockmark gullies, are buried by sediment transported by the bottom currents. Turbidity currents flowing downslope along the long pockmark gullies also erode the seafloor and make the NW slopes of the mud volcanoes less steep than those in the SE. Eddies imaged by the seismic sections may also play a role in transporting sediment to the deep sea in this area. Some of the reported fluid escape structures are still active, as indicated by the fluid pathways that reach the seafloor and plumes in the water column imaged by the seismic sections.

Mud extrusion and ring-fault gas seepage \u2013 upward branching fluid discharge at a deep-sea mud volcano

Submarine mud volcanoes release sediments and gas-rich fluids at the seafloor via deeply-rooted plumbing systems that remain poorly understood. Here the functioning of Venere mud volcano, on the Calabrian accretionary prism in ~1,600 m water depth is investigated, based on multi-parameter hydroacoustic and visual seafloor data obtained using ship-borne methods, ROVs, and AUVs. Two seepage domains are recognized: mud breccia extrusion from a summit, and hydrocarbon venting from peripheral sites, hosting chemosynthetic ecosystems and authigenic carbonates indicative of long-term seepage. Pore fluids in freshly extruded mud breccia (up to 13 °C warmer than background sediments) contained methane concentrations exceeding saturation by 2.7 times and chloride concentrations up to five times lower than ambient seawater. Gas analyses indicate an underlying thermogenic hydrocarbon source with potential admixture of microbial methane during migration along ring faults to the peripheral sites. The gas and pore water analyses point to fluids sourced deep (>3 km) below Venere mud volcano. An upward-branching plumbing system is proposed to account for co-existing mud breccia extrusion and gas seepage via multiple surface vents that influence the distribution of seafloor ecosystems. This model of mud volcanism implies that methane-rich fluids may be released during prolonged phases of moderate activity.

Recurring Emergence of the Mud Islands on Shelf of the Arabian Sea along the Makran Coast of Pakistan – Historical Perspective Using Remote Sensing Techniques

ABSTRACT Recurring emergences of mud islands on shelf of the Arabian Sea, along the Makran coast of Pakistan are now known to be submarine mud volcanoes. They are expressions of enhanced extrusions of fluidized mud and gases coupled with compressional tectonics in convergent margin settings. Since 1945 the Malan island has emerged four times, and some other mud islands have also been emerging repeatedly, at their own positions. The first known emergence, during November 1945, was concurrent with an earthquake of magnitude 8.0 (M8.0), the 2ndand 3rdemergences, in March 1999 and November 2010 respectively, were not related apparently with earthquakes. The 4themergence concurred with the Awaran earthquake (M7.7) of 24thSeptember 2013. Landsat images of March 1999 and November 2010 emergences indicate appearance of round-shaped island of 4.4 and 5.2 hectare area, followed by erosion and disappearance. The island was composed of mud breccias and circular vents spewing mud slurry and methane gas. The emergence of Malan island, in March 1999 and November 2010 was compared with earthquake data before and after the emergences. The earthquakes data, two years before March 1999 and November 2010 emergences and two years afterwards, shows correlation with both small and large earthquakes, prior to the emergence, in the radius of over 400 km. It is proposed that mud islands develop in response to the episodes of enhanced mud extrusion, which inturn are related with the enhanced compressional and/or seismic events. These events are followed by periods of relative quiescence characterized by normal activity of mud extrusion and marine erosion.

Structural boron as factor controlling illite crystallinity in a mud volcano environment (Northern Apennine, Italy)

Mud extrusion is a well-known phenomenon whereby fluid-rich, fine grained sediments ascend within a lithological succession due to their buoyancy. In this study of the terrestrial mud volcanism associated to an active thrusted area in the northern Apennines, we investigated the effect of boron incorporation in illite crystalline lattice. A significant variation was recorded on the investigated mud samples with respect to both the amount of fixed boron (118–529μg/g) and the full width at half-maximum height value (FWHM) of illite (0.29–0.62°Δ 2Θ). We attribute these variations to the interaction between boron-rich formation waters and the silty-clayey lithologies of the local sedimentary succession. The lack of any geographical correlation between the selected geochemical and mineralogical parameters is likely due to intensive thrust and fold deformation of the study area. Comparison of FWHM values with those from Dellisanti et al. (2008); Santerno succession, northern Apennine) lead us to suggest that application of FWHM as a depth indicator could be misleading within B-rich hydro-geological environments.

Penggunaan Sistem Informasi Geografis untuk Menghitung Dimensi Lumpur Panas di Porong, Sidoarjo

The hot mud extrusion in Porong, Sidoarjo since May 29, 2006 has impacted many aspects including social, culture, economy and transportation. Several weeks later, a collaborative team was formed to investigate the factors controlling the hot mud extrusions. One important aspect is concerning the mud dimensions such as its perimeter, area, volume and discharge. Bakosurtanal was assigned to carry out this task. Field surveys to acquire the mud heights were conducted twice within one month interval. Geographic Information System (GIS) using 3 dimentional approach was employed to compute the mud dimesions. One of the results show that the mud discharge is about 50.000 m3/day. This value was later commonly used to refer the magnitude of the hot mud.

Evidence of episodic long-lived eruptions in the Yuma, Ginsburg, Jesús Baraza and Tasyo mud volcanoes, Gulf of Cádiz

High-resolution single channel and multichannel seismic reflection profiles and multibeam bathymetric and backscatter data collected during several cruises over the period 1999 to 2007 have enabled characterising not only the seabed morphology but also the subsurface structural elements of the Yuma, Ginsburg, Jesus Baraza and Tasyo mud volcanoes (MVs) in the Gulf of Cadiz at 1,050–1,250 m water depth. These MVs vary strongly in morphology and size. The data reveal elongated cone-shaped edifices, rimmed depressions, and scarps interpreted as flank failures developed by collapse, faulting, compaction and gravitational processes. MV architecture is characterised by both extrusive and intrusive complexes, comprising stacked edifices (including seabed cones and up to four buried bicones) underlain by chaotic vertical zones and downward-tapering cones suggesting feeder systems. These intrusive structures represent the upper layer of the feeder system linking the fluid mud sources with the constructional edifices. The overall architecture is interpreted to be the result of successive events of mud extrusion and outbuilding alternating with periods of dormancy. Each mud extrusion phase is connected with the development of an edifice, represented by a seabed cone or a buried bicone. In all four MVs, the stacked edifices and the intrusive complexes penetrate Late Miocene–Quaternary units and are rooted in the Gulf of Cadiz wedge emplaced during the late Tortonian. Major phases of mud extrusion and outbuilding took place since the Late Pliocene, even though in the Yuma and Jesus Baraza MVs mud volcanism started in the Late Miocene shortly after the emplacement of the Gulf of Cadiz wedge. This study shows that fluid venting in the eastern sector of the Gulf of Cadiz promoted the outbuilding of large long-lived mud volcanoes active since the Late Miocene, and which have been reactivated repeatedly until recent times.

Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore of Costa Rica

Abstract. Large amounts of methane are delivered by fluids through the erosive forearc of the convergent margin offshore of Costa Rica and lead to the formation of cold seeps at the sediment surface. Besides mud extrusion, numerous cold seeps are created by landslides induced by seamount subduction or fluid migration along major faults. Most of the dissolved methane migrating through the sediments of cold seeps is oxidized within the benthic microbial methane filter by anaerobic oxidation of methane (AOM). Measurements of AOM and sulfate reduction as well as numerical modeling of porewater profiles revealed a highly active and efficient benthic methane filter at the Quepos Slide site, a landslide on the continental slope between the Nicoya and Osa Peninsula. Integrated areal rates of AOM ranged from 12.9 ± 6.0 to 45.2 ± 11.5 mmol m−2 d−1, with only 1 to 2.5 % of the upward methane flux being released into the water column. Additionally, two parallel sediment cores from Quepos Slide were used for in vitro experiments in a recently developed sediment-flow-through (SLOT) system to simulate an increased fluid and methane flux from the bottom of the sediment core. The benthic methane filter revealed a high adaptability whereby the methane oxidation efficiency responded to the increased fluid flow within ca. 170 d. To our knowledge, this study provides the first estimation of the natural biogeochemical response of seep sediments to changes in fluid flow.

Spatial association of mud volcano and sandstone intrusions, Boyadag anticline, western Turkmenistan

The mud volcano and sandstone intrusions complex occurring in the Boyadag anticline, western Turkmenistan, is the only well-documented example of co-existing, but not synchronous, mud volcanism and sand intrusion. Integrated field and laboratory evaluation investigates the spatial and genetic relations between the mud extrusion and the later sand intrusion. A sandstone dike and a pillar pierce mud volcano deposits on the crest of Boyadag anticline. Two more dikes occur near the escarpment caused by a crestal normal fault. The rising of mud and hydrocarbons from the Oligocene Maykop Fm. fed the mud volcano after the exposure of the Lower Pleistocene units at the core of the anticline. The main physical process that later led to sand fluidisation is identified as the progressive increase in pore fluid pressure, during a stage of reduced or null activity of the mud volcano, caused by the up-dip migration of hydrocarbons from the deep basin into the Pliocene sandstone reservoir within the Boyadag anticline. The hydrocarbons generated in the source rock levels of the Maykop Fm., whereas the saline water involved in the sand fluidisation is identified as the connate water of the Pliocene Red Beds Fm. The pressure rise was responsible for the fracturing of the sealing units, already weakened by the crestal normal fault and the mud volcano feeding system. The sand intruded into sealing units and mud breccia deposits, also using the mud volcano conduit and the crestal normal fault as preferential pathways. During the present-day background activity, the outcropping sandstone intrusions provide high permeability pathways for continuous fluid leakage, precluding the re-establishment of high pressures in the reservoir.

Composition and flux of explosive gas release at LUSI mud volcano (East Java, Indonesia)

AbstractThe LUSI mud volcano has been erupting since May 2006 in the densely populated Sidoarjo regency (East Java, Indonesia), forcing the evacuation of 40,000 people and destroying industry, farmland, and over 10,000 homes. Mud extrusion rates of 180,000 m3 d−1 were measured in the first few months of the eruption, decreasing to a loosely documented <20,000 m3 d−1 in 2012. The last few years of activity have been characterized by periodic short‐lived eruptive bursts. In May and October 2011, we documented this activity using high‐resolution time‐lapse photography, open‐path FTIR, and thermal infrared imagery. Gases (98% water vapor, 1.5% carbon dioxide, 0.5% methane) were periodically released by the bursting of bubbles approximately 3 m in diameter which triggered mud fountains to ∼10 m and gas plumes to hundreds of meters above the vent. During periods of quiescence (1–3 min), no appreciable gas seepage occurred. We estimate that LUSI releases approximately 2300 t yr−1 of methane, 30,000 t yr−1 of CO2, and 800,000 t yr−1 of water vapor. Gas bubble nucleation depths are >4000 m for methane and approximately 600 m for carbon dioxide; however, the mass fractions of these gases are insufficient to explain the observed dynamics. Rather, the primary driver of the cyclic bubble‐bursting activity is decompressional boiling of water, which initiates a few tens of meters below the surface, setting up slug flow in the upper conduit. Our measured gas flux and conceptual model lead to a corresponding upper‐bound estimate for the mud‐water mass flux of 105 m3 d−1.

Stratigraphy and paleoceanography of a topography-controlled contourite drift in the Pen Duick area, southern Gulf of Cádiz

Abstract The northern part of the Gulf of Cadiz has and still is receiving a lot of attention from the scientific community due to (among others) the recent IODP Expedition 339. In contrast, its southern part, or the Moroccan margin has received far less attention, although mud volcanoes, diapiric ridges and cold-water corals are present in this region. The El Arraiche mud volcano field is characterized by a compressive regime creating several ridges and assisting the migration of hydrocarbon fluids towards the seabed surface. This study presents seismic and multibeam evidence for the existence of a contourite drift at water depths between 550 and 650 m along the southwestern flank of the Pen Duick Escarpment and Gemini Mud Volcano, within the El Arraiche Mud Volcano field. From the onset of the Quaternary, when the escarpment started to lift and the local mud volcanism initiated, contouritic deposition was initiated as well at the foot of both topographic obstacles. Initially, fairly low-velocity bottom currents gave rise to sheeted drift deposits, affected by the uplift of the escarpment or mud extrusion. From the Middle Pleistocene onwards, separated mounded drift deposits were formed due to intensified bottom currents. An Antarctic Intermediate Water origin is inferred as driving mechanism for the drift development, although glacial conditions are not yet well constrained. The influence of Mediterranean Outflow Water (MOW) cannot be substantiated here. Moreover, the changes recorded within this contourite drift differ from the MOW-dominated contourite depositional system in the northern Gulf of Cadiz, as drift deposits only occur as early as the base of the Quaternary (compared to the Early Pliocene for the north) and mounded drift deposits only occur from the Middle Pleistocene onwards (compared to the Early Pleistocene). Cold-water coral mounds have been observed within and on top of the sedimentary sequence at the foot of the Pen Duick Escarpment. This implies that environmental conditions in which cold-water corals thrive were not necessarily restricted to the top of the Pen Duick Escarpment.

Newly discovered mud volcanoes in the Coastal Belt of Makran, Pakistan—tectonic implications

The Makran accretionary wedge has a much larger number of mud volcanoes then those reported earlier. Using high-resolution satellite images, over 70 active mud volcanoes were identified. These mud volcanoes occur within a well-defined zone; we call it the Makran zone of active mud volcanoes (MZAMV), which is parallel to the regional trend of the accretionary wedge. Mud volcanoes within the zone occur as clusters, which form linear belts parallel to the regional thrusts associated with anticlines. The MZAMV zone also includes the offshore mud volcanoes occurring in the shallow shelf area, including the recurrently emerging mud islands. Several occurrences of thick deposits of old mud volcanoes (Pleistocene or even older) are also present within this zone, which also display recognizable features that are characteristic of the fossil mud volcanoes. We propose that the MZAMV developed and evolved in response to the continued compression within the Makran accretionary wedge, which in turn, is a response of the subduction process. Mud diapirism has been an ongoing phenomena since Pleistocene or even earlier. The events of enhanced mud extrusion in mud volcanoes and/or emergence of island(s) have relevance with seismic phenomena and, therefore, may be closely monitored.

Petrogenesis of Na-rich paralava formed by methane flares associated with mud volcanism, Altyn-Emel National Park, Kazakhstan

High-Na slag-like rocks (paralava) with 4.5–11 % Na2O from the Altyn-Emel mud volcanic field, Kazakhstan, are the products of melting of sediment + salt mixtures by methane flares associated with mud extrusion. The main minerals of the paralavas are diopside and wollastonite which have quench morphologies. Other high-temperature phases (crystallizing from melt and vapour phase) are tridymite, cristobalite, chlorapatite, alkali feldspar, pyrrhotite, native iron and silicon, iron phosphides, titanite, rutile, and carbon. The paralavas lack the Na–Ca silicates devitrite and combeite, but have high-Na and Na–K glasses that have not been homogenized despite low viscosities of <10−3.5 Pa s. The large number of ignition foci in the Altyn-Emel mud volcano field indicates gas venting from small, shallow reservoirs. The methane flares are inferred to have been small and the fire events short-lived. Fires were extinguished once overpressure released during eruption, methane venting stopped and melted rocks rapidly quenched. The periodicity of eruptions and methane flaring most likely depends on the recurrence of earthquakes (M < 5) which are frequent in this tectonically active area.