Mud volcanoes in the Northern Apennines (Italy) and South Caspian Basin (Azerbaijan): common and distinctive peculiarities, and general implications

Project leaders

Marco Bonini, Akper Feyzullayev

Agreement

AZERBAIJAN - ANAS-not in force - Azerbaijan National Academy of Sciences

Call

CNR/ANAS 2012-2013

Department

Earth and Environment

Thematic area

Earth system science and environmental technologies

Status of the project

New

Research proposal

The Northern Apennines (Italy) and the Greater Caucasus (Azerbaijan) are two fold-and-thrust belts located within the Alpine-Himalayan tectonic belt. The present-day structures of these belts are still controlled by the ongoing collision of the Arabian and African plates with Eurasia (e.g., Philip et al., 1989; Dewey et al., 1989; Axen et al., 2001; Jackson et al., 2002). They share a very similar time-space deformation history that regards a number of regional aspects, particularly the presence of active and seismogenic structures controlling and deforming large foreland basins filled by synorogenic sediments. These basins are the Po Plain, settled ahead of the exposed Northern Apennines in Italy, and the South Caspian Basin, which is positioned along-strike the Grater Caucasus in Azerbaijan.
Other features common to both belts concern a number of aspects, such as (1) the presence of a thick Mesozoic-Quaternary sedimentary cover, (2)  recent and ongoing tectonic activity manifested by relevant seismicity, horizontal and vertical movements of the Earth's crust accompanied by severe dislocation of sediments operated by widespread fold and thrust fault systems, (3) high sedimentation rates within the foreland basins, especially during Pliocene-Quaternary times, (4) very low geothermal gradient (20-15oC/km), together with the development of relevant fluid overpressures, (5)  occurrence of hydrocarbon reservoirs, and (6) mud volcanism and diapirism, which is generated by the expulsion of fluids (i.e., saline waters, methane) and rock fragments/blocks from subsurface clastic deposits, producing the typical conic-shaped extrusive features that in Azerbaijan may be as tall as 300-500 m, being Azerbaijan the locus hosting the largest onshore mud volcano features (Guliyev and Feizullayev, 1997).
We focus our research on mud volcanism, which is strongly coupled with many of the abovementioned aspects, specifically the occurrence of (1) hydrocarbon accumulations and (2) fluid overpressures (Feyzullayev and Lerche, 2009), as well as (3) a number of features connected with tectonics (Jakubov et al., 1971; Bonini, 2007). Although these areas display, mainly qualitative, common features, at the same time they hold some distinctions in Petroleum systems and mud volcanism due to the local peculiarities of their geological structure. More specifically, in the Northern Apennines, mud volcano features of relatively small size essentially localise along a relatively narrow belt extending in a roughly WNW-ESE direction along the foothills of the Pede-Apennine margin. Here, a potentially seismogenic SSW-dipping thrust system has been lifting the exposed orogenic wedge, separating this latter from a belt buried beneath the Po Plain deposits (Benedetti et al., 2003; Boccaletti et al., 2004; Bonini, 2007). Mud volcanism in Azerbaijan is instead characterized by much larger features, and is widespread across the whole exposed belt as well as undersea the South Caspian Basin (Jakubov et al., 1971). The Northern Apennines and the Grater Caucasus may be thus viewed as two end-members in mud volcano distribution that may reflect different tectonic settings and structural controls, being the former related to a single regional structure (the thrust system underlying the Pede-Apennine margin), and the latter associated with the several fold trains deforming the whole region.
In both thrust belts, mud volcanism typically occurs at thrust anticlines, particularly those associated with active shortening, and is characterised by paroxysmal activity that is occasionally clearly linked to seismic waves released by ‘triggering' earthquakes (Guliyev and Feizullayev, 1997; Mellors et al., 2007; Bonini, 2009). Mud volcanism is therefore apparently connected to active tectonic compression, but a number of processes remain to be assessed satisfactorily, for instance (i) the mechanisms and conditions that allow the fluids to rise from great depths, (ii) the time-space migration patterns of such deep-sourced fluids, (iii) the relations of mud volcanism with seismogenic structures and earthquakes, and (iv) the chemical-physical processes controlling the hydrocarbon production at depth.
The project activity will start from the revision of early studies with the purpose of identifying the common and distinctive features concerning geological and geomorphological structure, relations with fault tectonics, geochemical information, overpressures and recent geodynamics (seismicity, horizontal Earth's crust movements). The research will consider and integrate the various skills present on both parties.
This project will consider field trip investigations on some Italy and Azerbaijan mud volcanoes with the goal of gas and water sampling, as well as measurements of Radon and methane fluxes, radioactivity, and temperature of mud cover specifying coordinates of studied mud volcano elements using GPS devices. The isotopic characterization of gases emitted from mud volcanoes, as well as their chemical composition, integrated with the calculation of gas formation depth (hypsometric and stratigraphic), will concern the light hydrocarbons (C1-C10 compounds), CO2, H2S and N2, as well as the geochemistry of saline waters. Such geochemical analyses aim to reveal the occurrence or the absence of variations across an active fold-and-thrust belt, and for this they will focus on selected transects across both active chains - i.e., from the interior toward the chain front. Owing to the different distribution of mud volcanism outlined above, possible across-strike geochemical variations may be determined in the Greater Caucasus, where mud volcanoes are extensively distributed. In contrast, only along-strike variations might be determined in the Northern Apennines, being here mud volcanoes dominantly occurring along a relatively narrow belt at the Pede-Apennine margin. However, the consideration of both fold-and-thrust belts, which may typify two different categories (and likely end-members) of mud volcano distribution, is crucial for assessing a general model of mud volcanism.  
A detailed investigation of the tectonic structures controlling the migration of subsurface fluids (including hydrocarbons) generating the mud volcanism will integrate the collection of the various datasets mentioned above. The structural analysis will employ the classical techniques of structural geology, and will be conducted in key areas chosen in both fold-and-thrust belts, along or nearby the sampled geochemical transects. In this frame, the relations of mud volcanism with active and potentially seismogenic structures will focus on specific elements, such as the regional thrust lifting the Pede-Apennine margin, and the trains of thrust folds marking the boundary between the Greater Caucasus and its foreland basin (Kura Basin). In particular, the structural analysis will address the tectonic structures hosting mud volcanism (mostly anticlines), paying special attention to the brittle elements controlling fluid escape at surface. This analysis will be integrated by estimates of vertical movements and their rates through apatite fission-track (AFT) thermochronology. Whereas these data are available in the Northern Apennines, they are almost absent in the Azerbaijan Caucasus, which will be therefore targeted by this methodology.
REFERENCES
Axen, G.J., P.S. Lam, M. Grove and Stockli, D.F. (2001). Exhumation of the westcentral Alborz mountains, Iran, Caspian subsidence, and collision-related tectonics, Geology, 29, 559-562.
Benedetti, L. C., P. Tapponnier, Y. Gaudemer, I. Manighetti, and J. Van der Woerd (2003). Geomorphic evidence for an emergent active thrust along the edge of the Po Plain: The Broni-Stradella fault, J. Geophys. Res., 108(B5), 2238, doi:10.1029/2001JB001546.
Boccaletti, M., M. Bonini, G. Corti, P. Gasperini, L. Martelli, L. Piccardi, C. Tanini, and G. Vannucci (2004), Seismotectonic map of the Emilia-Romagna region, scale 1:250,000, with explanatory notes, Soc. Elaborazioni Cartogr., Florence, Italy.
Bonini, M. (2007). Interrelations of mud volcanism, fluid venting, and thrust-anticline folding: examples from the external northern Apennines (Emilia-Romagna, Italy). J. Geophys. Res. 112, B08413. doi:10.1029/2006JB004859.
Bonini, M. (2009). Mud volcano eruptions and earthquakes in the Northern Apennines and Sicily, Italy. Tectonophysics 474, 723-735.
Dewey, J.F., Helman, M.L., Turco, E., Hutton, D.H.W., Knott, S.D., (1989). Kinematics of the western Mediterranean. In: Coward, M.P., Dietrich, D., Park, R.G. (Eds.), Alpine ectonics. Geological Society, London, Special Publication, pp. 265-283.
Feyzullayev, A.A. and Lerche, I., (2009). Occurrence and nature of overpressure in the sedimentary section of the South Caspian Basin, Azerbaijan. Energy Exploration & Exploitation 27(5), 345-366
Guliyev, I.S., Feizullayev, A.A. (1996). Geochemistry of hydrocarbon seepages in Azerbaijan. In: Schumacher, D., Abrams, M.A. (Eds.), Hydrocarbon migration and its near surface expression. AAPG Memoir 66, 63-70.
Guliyev, I.S., Feizullayev, A.A. (1997). All about Mud Volcanoes. Baku Institute of Geology of the Azerbaijan National Academy of Sciences, Nafta Press, Baku, Azerbaijan, 52 pp.
Jackson, J, K. Priestley, M.B. Allen and M. Berberian. (2002). Active tectonics of the South Caspian Basin. Geophysical Journal International, 148, 214-245.
Jakubov, A., A. Ali-Zade, and Zeinalov M. (1971), Mud Volcanoes of the Azerbaijan, SSR, Publ. House of the Acad. of Sci. of the Azerbaijan SSR, Baku. 256 pp.
Mellors, R., Kilb, D., Aliyev, A., Gasanov, A., Yetirmishli, G. (2007). Correlations between earthquakes and largemud volcano eruptions. J.Geophys. Res.112, B04304. doi:10.1029/2006JB004489.
Philip, H., Cisternas, A. Gvishiani A., Gorshkov A. (1989). The Caucasus: an actual example of the initial stages of continental collision, Tectonophysics, 161, 1-21.

Research goals

This project aims to define the main aspects related to mud volcanism, and for this it considers the Northern Apennines and particularly the Greater Caucasus-South Caspian Basin, where mud volcanism exhibits the largest manifestations on Earth. The results of this joint research are expected to gain further insights and a better understanding of the mechanisms of formation and activity of mud volcanism in the studied areas, and thus the project results may hold a number of relevant implications that are outlined below:
1) General importance related to a better understanding of the various controls on mud volcanism processes, particularly the role of tectonic structures and the associated vertical movements  in allowing the upraising of deep-sourced fluids, as well as the characterization of these fluids in terms of fluid geochemistry and pressure-temperature conditions.
2) Characterization of the isotopic and compositional features of gases emitted from mud volcanoes. This analysis aims to reveal (i) the characteristics of the fluid sources, (ii) the occurrence or absence of geochemical variations across an active fold-and-thrust belt, and (iii) how these may relate to the time-space evolution of tectonic activity.
3) Besides a better comprehension of the mud volcanism processes, the integration and complex interpretation of the gathered datasets may also contribute to a better definition of a general model of mud volcanism. In addition to an academic interest, this model may also hint for other aspects spanning from those economical related to petroleum prospectivity, to those of social interest, such as the seismic hazard and the implications connected with the input into the atmosphere of greenhouse gases (mostly methane and other light alkenes) emitted from the mud volcanoes.

Last update: 06/07/2025