**5. The Ross Sea**

In the last two decades, the Ross Sea Embayment area has been considered a laboratory of growing interest for the reconstruction of the past Antarctic environment, the onset of Antarctic Eocene-Paleocene glaciation, climates studies, the understanding of the tectonic deformation and global sea level changes that all have driven glacial history [23].

The main Ross Sea elongated N-S sedimentary troughs, such as the Victoria Land Basin, the Drigalsky Basin, the northern continuation of the Northern Basin, the Central Basin, the Joides Basin and the Eastern Basin are bounded by basement highs and morphological banks. They were formed during the late Cretaceous major rifting phase and later during the Cenozoic, while a widespread igneous activity affected the West Antarctic Rift System ([23] and references therein).

The potential presence of gas hydrate is supported by the identification of hydrocarbons in the Ross Sea area. In fact, in the central and eastern Ross Sea, the cored Miocene muddy sediments at the DSDP sites showed high contents of total hydrocarbon gas (mainly methane; [61]). In the western Ross Sea, analysis of sediments from gravity cores showed the presence of hydrocarbon gases with low concentrations of methane [62] and in the McMurdo Sound, both CIROS-1 and MSSTS-1 wells, detected small amount of organic carbon [63, 64]. Moreover, [65] supposed the presence of a BSR, an indirect indication of the presence of gas hydrate, on a seismic line, located in the Victoria Land Basin. Moreover, in the same part of the Ross Sea, an extensive field of pockmarks at 450–500 m depth and unusual flat-topped seafloor mounds was identified on a detailed multibeam dataset [66, 67]. One hypothesis discussed by the authors is that these features may be carbonate banks because of their proximity to the inferred subsurface gas hydrate, although their preferred interpretation is that the features are of volcanic origin.

At this stage, to confirm or refuse the presence of gas hydrate in the Ross Sea more measurements are necessary. Recently, [23] performed a modeling of the base of gas hydrate stability based on the steady-state approach by using literature data, such as bathymetric and well data, sea bottom temperature, a variable geothermal gradient and assuming that the natural gas is methane, in order to identify the areas where the gas hydrate stability is verified The modeling was performed in the whole Ross Sea (**Figure 8**).

The results from the modeling suggested that depth and distribution of the base of the gas hydrate stability zone are correlated with the bathymetry. In fact,

**Figure 8.**

*Distribution of the base of the gas hydrate stability zone from the seafloor (in meters). The geothermal gradient is supposed to be equal to 49°C/km (modified after [23]).*

in proximity of the banks, the gas hydrate stability zone results display thickness less than 100 m. On the other hand, the thickness of the gas hydrate stability zone increases in proximity of the basins to values exceeding 400 m related to bathymetry increase and seafloor temperature decrease. Moreover, the existence and dynamics of the gas hydrate distribution is strictly related to the existence and evolution of the shallow geological and geomorphological features below the sea floor, as suggested in the past by several authors. So, the presence of some geological and geomorphological features are in agreement with the gas hydrate presence in this part of Antarctica [23].
