**2. The South Shetland Margin (the Antarctic Peninsula)**

As mentioned before, the Polar Regions and, in particular, the transition zones, such as the Antarctic Peninsula, are strongly affected by the climate signals. For this reason, several studies are focused on characterizing the South Shetland Margin and the gas hydrate reservoir here present. In the following, we resume the main results related to the geophysical studies.

#### **2.1 Geological setting**

The SSM is located in the northeastern tip of the Pacific margin of the Antarctic Peninsula, characterized by the subduction of the Antarctic and the former Phoenix plates beneath the South Shetland micro-continental block. Along the continental margin, a trench-accretionary prism-fore-arc basin sequence can be recognized (i.e., "in [24, 25]"). The Phoenix plate started to subduct beneath the Antarctic plate from late Paleozoic time [26] and progressed from the southwest to the northeast along the margin. Active spreading at the Antarctic Phoenix ridge ceased about 4 Ma ago [27], when the last ridge-crest segment of the Phoenix plate reached the south margin of the Hero Fracture Zone. The subduction process is presently believed to have taken place as a result of sinking and roll-back of the oceanic plate coupled with the extension of the Bransfield Strait marginal basin (i.e., "in [24, 27]"). The Phoenix plate is from about the Shackleton Fracture Zone to the northeastern side, while by the Hero Fracture Zone to the southwestern side, which intersect the continental lithosphere.

### **2.2 Geophysical data**

Different Antarctic expeditions have taken place off the Antarctic Peninsula, in order to verify the existence of a potential gas hydrate reservoir and to reconstruct

**5**

**Figure 3.**

*Figure 6.*

*Gas Hydrates in Antarctica*

data were acquired.

an area of about 5500 km<sup>2</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.94306*

the interstitial fluid analyses to detect gas presence.

**2.3 Gas hydrate and related features**

the tectonic setting of the margin. In this region, the presence of the diffused and discontinuous BRS was discovered during the Italian Antarctic cruses of 1989–1990, 1996/1997, and 2004–2005 onboard the R/V OGS-Explora within the framework of a research program supported by the Italian National Antarctic Program (PNRA; i.e., **Figure 3**; [28–33]. During the first leg, only seismic data were acquired, while during the last two legs Ocean Bottom Seismometer (OBS) and other geophysical

The multidisciplinary dataset, including multibeam bathymetry, seismic profiles (multichannel seismic and OBS data and chirp), and two gravity cores clearly shows active mud volcanism sustained by hydrocarbon venting in the region. The multibeam bathymetric data was indispensable to reconstruct the seabed, covering

tion or the presence of faults were detected by chirp sub-bottom profiles. The two gravity cores recover 1.07 m and 2.98 m of sediment. Several laboratory measurements were performed on these cores, such as the computer aided tomography and

The bathymetric map of the SSM provides evidence of four mud volcanoes (**Figure 3**; [18, 31]), which are associated to the presence of gas hydrate. This active mud volcanism might be favored by the reactivation of pre-existing faults and weakness zones because of the regional extensional tectonics of the South Shetland trench and margin [34], the adjacent Bransfield Strait back-arc basin [35], and the

*Map of the investigated area with the location of the acquired data during the surveys. Red rectangle indicates the seafloor reflectivity reported in Figure 5. Green rectangles indicate the position of the zoom reported in* 

complex tectonic interaction at the Elephant Island triple junction [36].

slides and fluid expulsion related to gas hydrate dissocia-

### *Gas Hydrates in Antarctica DOI: http://dx.doi.org/10.5772/intechopen.94306*

*Glaciers and the Polar Environment*

**2. The South Shetland Margin (the Antarctic Peninsula)**

results related to the geophysical studies.

intersect the continental lithosphere.

**2.2 Geophysical data**

**2.1 Geological setting**

**Figure 2.**

*presence in literature.*

As mentioned before, the Polar Regions and, in particular, the transition zones, such as the Antarctic Peninsula, are strongly affected by the climate signals. For this reason, several studies are focused on characterizing the South Shetland Margin and the gas hydrate reservoir here present. In the following, we resume the main

*Map of Antarctica showing the potential areas, indicated by points, where there are indication of gas hydrates* 

The SSM is located in the northeastern tip of the Pacific margin of the Antarctic Peninsula, characterized by the subduction of the Antarctic and the former Phoenix plates beneath the South Shetland micro-continental block. Along the continental margin, a trench-accretionary prism-fore-arc basin sequence can be recognized (i.e., "in [24, 25]"). The Phoenix plate started to subduct beneath the Antarctic plate from late Paleozoic time [26] and progressed from the southwest to the northeast along the margin. Active spreading at the Antarctic Phoenix ridge ceased about 4 Ma ago [27], when the last ridge-crest segment of the Phoenix plate reached the south margin of the Hero Fracture Zone. The subduction process is presently believed to have taken place as a result of sinking and roll-back of the oceanic plate coupled with the extension of the Bransfield Strait marginal basin (i.e., "in [24, 27]"). The Phoenix plate is from about the Shackleton Fracture Zone to the northeastern side, while by the Hero Fracture Zone to the southwestern side, which

Different Antarctic expeditions have taken place off the Antarctic Peninsula, in order to verify the existence of a potential gas hydrate reservoir and to reconstruct

**4**

the tectonic setting of the margin. In this region, the presence of the diffused and discontinuous BRS was discovered during the Italian Antarctic cruses of 1989–1990, 1996/1997, and 2004–2005 onboard the R/V OGS-Explora within the framework of a research program supported by the Italian National Antarctic Program (PNRA; i.e., **Figure 3**; [28–33]. During the first leg, only seismic data were acquired, while during the last two legs Ocean Bottom Seismometer (OBS) and other geophysical data were acquired.

The multidisciplinary dataset, including multibeam bathymetry, seismic profiles (multichannel seismic and OBS data and chirp), and two gravity cores clearly shows active mud volcanism sustained by hydrocarbon venting in the region. The multibeam bathymetric data was indispensable to reconstruct the seabed, covering an area of about 5500 km<sup>2</sup> slides and fluid expulsion related to gas hydrate dissociation or the presence of faults were detected by chirp sub-bottom profiles. The two gravity cores recover 1.07 m and 2.98 m of sediment. Several laboratory measurements were performed on these cores, such as the computer aided tomography and the interstitial fluid analyses to detect gas presence.
