Deep-fluids migration

One of the main research themes of the Sedimentary Basins Research Group is the study of spontaneous seepage of deep fluids, including hydrocarbons and connate waters. Cold seepage frequently involves the emission of methane gas, which dynamics must be understood in greater detail. The seafloor sediments host enormous volumes of methane that can be sequestered by gas hydrates and/or escape through natural gas leakage. Cold seeps have also an incredible impact on the submarine ecosystems, supporting chemosynthesis-based benthic organisms, and on the geological evolution of the surrounding areas.

Gas chimneys australia
Gas chimneys above a leaking reservoir, offshore NW Australia

We use a multidisciplinary and integrated approach to resolve the genesis and evolution of features associated with cold seepage, such as methane-derived carbonates and mud volcanoes. We explore the significance of cold seeps, such as:

  • It is evident that we need to know more about the processes that controlled the methane release in the geological past. Without knowing these processes more in detail, predictions for the future will always suffer a higher uncertainty.
  • The occurrence of methane in surficial sediments generates a rough seafloor topography in the form of mounds/highs or depressions. We can identify the genesis of these morphologies in a combination of diagenetic alteration of the sediments, erosion, and expansion or destabilization of the seafloor.
  • Methane hydrates and free gas can be primers for submarine slope failures. What is the relationship among cold seeps evolution, structural setting, and submarine slope instability?
  • What information can we obtain from cold seepage to better understand subsurface fluid migration and hydrocarbon generation? Cold seeps are a fantastic and economic tool to understand the petroleum system both in frontier and known basins.

Methane-Derived Authigenic Carbonates

MDAC Enza River, Italy
Methane-derived carbonate chimney cropping out along the Enza riverbed, N. Italy

Methane-derived authigenic carbonates are one of the main byproducts of methane flow in the near-seafloor subsurface. We investigate their role as a record of past and present methane emission.

Despite the understanding of methane-derived carbonates increased in the last decade, various topics remain poorly solved. Important questions that need better answers are, for example: how we can best interpret the significance of isotopes to relate migrating fluids with authigenic carbonates? What is the relative contribution of marine water versus deep connate water during the carbonates precipitation? Which are the biogeochemical signatures recorded in the carbonates that can provide accurate information on the fluids migration mechanisms in different lithologies?

Mud volcanoes

MV Rivalta
Small mud volcano emitting methane and oil, N. Italy

Mud volcanoes are hazards as their mud flows can destroy infrastructures. The Sidoarjo Mud Volcano in North Eastern Java, which suddenly erupted in 2006, within weeks submerged several villages with boiling mud, forcing thousands from their homes. Scientists extensively debated the formation of Sidoarjo and proposed contrasting trigger mechanisms for its genesis (here and here). This discussion is a perfect example of the large uncertainties still present in our understanding of the phenomenon.

We investigate the processes governing the birth and evolution of mud volcanoes, with particular attention to their interaction with and influence on the surrounding geological environment. We use the geochemical information derived from connate water and hydrocarbon emitted by mud volcanoes to improve the characterization of the petroleum system at depth.

Mass Transport Deposits

Despite the Gulf of Mexico being one the most explored basins worldwide, the near-seabed and shallow subsurface of deep and ultra-deep water (> 1000m) are still poorly known. Only in the last 15 years the extensive use of AUV-borne mapping systems started to depict surficial morphology and shallow subsurface geology with adequate details and resolution. The main result is that these areas are active and dynamic. Particularly interesting in the Gulf of Mexico is to understand the genesis and architecture of Mass Transport Deposit (MTDs).

The internal structures and extents of the MTDs have been characterized in several areas of the Gulf of Mexico using hydrocarbon exploration 3D seismic data. However, these data resolution provides a good understanding only of the large MTDs and of the deformation history up to the base of Pleistocene. Therefore, the detailed characterization of smaller-scale deposits emplaced during the most recent time interval is missing. Using an analogy with classic sequence stratigraphy, we have a wealth of information about the low order structures but not about the high order systems

MTD in the offshore Gulf of Mexico

Tsunami and extreme waves  sedimentology

Tsunamis are the most famous and destructive results of coastal earthquakes, in part because they can cause damage thousands of miles from the earthquake epicenter. Typically, two small local tsunamis occur each year throughout the world. Instead, major tsunamis are infrequent events that may hit the same portion of coastline with a recurrence time of centuries. Even on a tectonically active coastline, the most recent large tsunami may predate the written record (e.g. 1700 Cascadia).

Researchers have spent decades comparing the results of models of ancient tsunamis to the deposits of modern tsunamis. In the last three decades, geologists have been to most areas hit by tsunamis soon after the event (starting with 1992 Nicaragua), and in each case sedimentologists have collected data to help benchmark models of tsunami deposition. We still don’t know exactly what processes affect the tsunami sediments nor how much of the original deposit is returned to the ocean.

We focus on tsunami and storm sedimentation, in an effort not only to understand how to identify ancient catastrophes from their deposits but to determine how large those catastrophes were and the processes acting on their sediments after deposition.

Tuscaloosa Marine Shale

The Gulf of Mexico experienced various anoxic events during the Cretaceous that are now preserved in the sedimentary record as organic-rich black shales. One example is within the Tuscaloosa Group, which comprises a complete second-order depositional sequence with the Cenomanian-Turoninan Tuscaloosa Marine Shale (TMS) corresponding to the inundated phase after transgression.

Although the economic potential of the TMS has been extensively evaluated by the O&G industry, TMS’ sedimentology and stratigraphy remain relatively under-investigated at the basin scale. While several studies developed a depositional model for the TMS, most relied solely on well-log data. We work on expanding our knowledge of TMS deposition by analyzing recovered cores.