Plenary lecture

Plenary lecture, Tuesday 10th, September, h. 10:00, Aula Magna, Introduced by Conference Honorary Chair Prof. Emiliano Mutti

Adriano R. Viana – Petrobras S.A.

Petroleum exploration is an industrial activity where different kinds of risks are part of the business. Besides political, market and costs risks, and in order to evaluate the potential of a sedimentary basin to become a prolific oil and/or gas province, it is of paramount importance to identify and quantify the geological risks of finding an active petroleum system. Primary guidelines are ensuring high success rate and optimum geohazards assessment.
Exploration has moved to deeper waters in the last decades stimulated by new discoveries in frontier areas supported by leading edge technology that yields better reservoir imaging, higher drilling performance in hostile settings and the acquisition of a huge amount of GGG data. A robust interpretation of the depositional systems developed in the deeper portions of the continental margins is hence a fundamental step to characterize the critical elements of a petroleum system with special emphasis on source and reservoirs rocks.
The understanding of how deep water depositional systems are formed and evolve through time depends on the sum of many factors. The correct identification of the physical and chemical processes responsible for sediments transport/accumulation/erosion /growth, the physiographic context of the basin, the circulation pattern of the margin, the availability of sediments, the characteristics and the controls on lateral and vertical sediment distribution are some of the aspects that must be tackled.
The remoteness of the deep water settings makes any kind of direct observation of the present day processes and the sedimentary records on this realm dependent on a high cost, complex data acquisition.
The petroleum industry provides part of these data, scientific expeditions some other, which must be added to the basic knowledge derived from outcrop studies and physical and numerical simulations. The huge amount and diversity of data that has been accumulated along many years of investigation can only be fully exploited with the help of high-performance computational devices and the use of artificial intelligence technology.
The association of modern technology with vintage methods aiming to interpret depositional systems will only be successful if a strong sedimentological background is considered as a pre-requisite for the geoscientists who want to extract knowledge from data.

Plenary lecture, Wednesday 11th September, h. 11:30, Aula Magna, Introduced by Conference Honorary Chair Prof. A. Bosellini

Sam Purkis – University of Miami

What is a complex system? A universal characteristic of a complex system is that the whole is greater than, and often significantly different from, the simple linear sum of its parts. In many instances, the whole appears to act in a manner dissociated from the specific characteristics of its individual building blocks. Reef ecosystems are a case in point. No individual reef architect has any sense of the grand enterprise to which it is contributing. But as a collective ecosystem, vast carbonate edifices are constructed with a coherent and intricate morphology (Fig. 1, for instance). This collective outcome, in which a system manifests significantly different characteristics from those resulting from simply adding up all of the constituent parts, is termed ‘emergent behavior’. A special case of emergent behavior is ‘self-organization’, where the constituents of a system agglomerate themselves to form the emergent whole.
Although there have been many efforts to evaluate complexity in shallow-water carbonate deposits, studies in this realm have primarily focused on long-term and large-scale processes, such as the provision of accommodation space (e.g. between greenhouse and icehouse climatic regimes) and the facies geometries that these changes yield. However, it is also well recognized that the growth fabrics of which carbonate depositional systems are built, emerge from tightly-integrated systems of abiotic and biotic components. It is recognized too that these components display a myriad of organism-environment feedbacks operating on different length scales. Configured as such, carbonate depositional environments have the potential to generate complex facies anatomies through self-organization. And, as coral reefs illustrate with depressing effectiveness, a small perturbation in one part of a self-organized system can have radical consequences elsewhere. In 1983-1984, for instance, the sea urchin Diadema antillarum suffered mass mortality throughout the Caribbean. On face value, an inconsequential component of a sprawling reef ecosystem, but the demise of this herbivore contributed to a disastrous phase shift of the region’s reefs from coral to algal-dominated, a configuration which persists today. Such are the non-linear sensitivities of complex ecosystems and the motivation for understanding them.
Reef systems exhibit at least two behaviors consistent with self-organization as a structuring force. First, 30% of platform-interior reefs globally exhibit reticular regular patterning, a behavior recognized as far back as the Upper Paleozoic (e.g. Purkis et al., 2005). Second, the patterning of modern and ancient reef systems displays remarkably universal, systematic, and predictable relationships which describe how the shape and separation of depositional elements scale with size (Fig. 1D). Whereas the processes underpinning these remarkable regularities are poorly understood, their existence suggests a common conceptual framework to underly the patterning of both modern and ancient reefs, regardless of their biological architects – surely an excellent hunting ground for comparative sedimentologists.
With the production and accumulation of carbonate fabrics intrinsically tied to life, any advance in the understanding of the myriad of organism-environment feedbacks that serve to structure carbonate depositional systems over geological timescales, will also aid in understanding function over shorter ecological timescales. Again, this is particularly true for coral reefs. With compelling evidence that half the world’s reefs have been lost over the last four decades, there is urgent motivation to better understand the nature of the disruptions that are conspiring to devastate this iconic carbonate ecosystem.

Plenary lecture, Friday 13th, September, h. 10:30, Aula Magna, Introduced by Conference Honorary Chair Prof. F. Ricci Lucchi

Alessandro Amorosi – University of Bologna, Italy

Over the past two decades, the sequence stratigraphy of Quaternary alluvial, deltaic, and coastal successions has expanded in an exciting direction of research. In recent years, Quaternary geology has become relevant to the oil and gas exploration and shallow subsurface Late Pleistocene to Holocene datasets have been increasingly used at sub-seismic scales for the characterization of reservoir architecture and prediction of petrophysical properties. Recent advances in unconventional reservoir characterization have placed significant attention on mud dispersal, deposition, and diagenesis, emphasizing the need for a multi-disciplinary approach to the facies analysis of mud-prone sediment bodies.
Holocene successions worldwide exhibit recurring and predictable motifs in stratigraphic architecture and shoreline trajectory that can be delineated objectively and that reflect the overwhelming dominance of post-glacial eustatic change on sedimentation. Quantitative sediment fluxes data can be extracted reliably from late Quaternary sediment-routing systems, as these systems offer excellent stratigraphic correlation on short-term observational periods. Holocene stratigraphy, in particular, is confidently constrained by numerical dating, and can be seen as a potential bridge between the observable and measurable modern depositional processes and interpretation of stratal architecture in the ancient record.
Architectural-stacking patterns of Holocene coastal wedges have been used historically for the interpretation of transgressive-regressive trends from different sedimentary basins around the world. The synchronous initiation of Holocene marine deltas by deceleration of eustatic rise, 8500 to 6500 years ago, is one of the few well-documented examples of worldwide coastal system response to relative sea-level fluctuations, at the turnaround from transgressive to highstand conditions.
SEPM Special Publications 41 and 51, from the late 80s and the early 90s, respectively, made the stratigraphic record of Quaternary sea levels and facies models of incised valley systems accessible to the broader sedimentologic (and sequence stratigraphic) community. The recent development of source-to-sink concepts has emphasized the ability to generate numerical and physical models of surface processes and their stratigraphic results using the Quaternary record.
The stratigraphic analysis of buried Quaternary strata can have practical limitations compared to exceptionally exposed outcrop cases. In subsurface studies, facies analysis is limited to core-scale sedimentary structures and reconstruction of stratal geometries is made difficult by low data density. Despite these limitations, data extractable from late Quaternary cores offer unique opportunities for high-resolution sequence stratigraphic analysis. Potential advantages of the late Quaternary record over ancient deposits include:
precise and accurate techniques for age determination, due to the applicability of multiple geochronometers, such as radiocarbon dating, optically stimulated luminescence, mollusk aminostratigraphy, mollusk U-series, electron spin resonance, and cosmogenic radionuclides;
a huge body of knowledge about late Quaternary climate change and eustatic history that permits the examination of stratigraphic architecture and environmental evolution in response to glacial–interglacial fluctuations and base-level changes;
changes in tectonic forcing during the narrow time window of the late Quaternary are at a minimum, and primary stratigraphic relations between adjacent depositional systems are commonly preserved;
late Quaternary paleogeography was quite similar to the modern, and comparable sediment-routing systems developed, with only minor changes in depositional regimes and river network under glacial (lowstand) conditions;
late Quaternary fossil assemblages closely resemble modern bioassemblages and therefore can serve as a basis for detailed and accurate facies interpretation;
Quaternary cores allow accurate characterization of mud-dominated facies, often obscure in outcrop. A comprehensive program of sample analysis (sediment composition and fossil content) in the mud size range provides the information to discriminate subtle changes in environmental conditions and shifts in sediment provenance within seemingly homogeneous facies. Fine-grained deposits can also elucidate sedimentary processes tied to climate change inferred from record of past vegetation cover;
late Quaternary sediments did not undergo strong diagenetic modifications and provide the basis to constrain rock properties without confounding weathering effects.
Stratal stacking patterns are the core of sequence stratigraphy and terms that imply a relationship between sea level and systems tract should preferentially be avoided when interpreting the ancient record. In this regard, the late Quaternary record plays an important “educational” role, as it is one of the few places where stacking-pattern, systems-tract, and sea-level terminologies meet and can be used almost interchangeably.
There is an evident increase in the resolution of stratigraphic studies and the sequence stratigraphy of Quaternary successions is expanding its scope to include applications to a variety of data sets, over a range of time scales. The best insights into the quantification of the finest stratigraphic scales are provided by the high-resolution studies of the Holocene, which have the ability to quantify depositional systems and their changes on 102-103 yrs timescales. The Quaternary record cannot be applied to all climatic conditions (e.g., icehouse versus greenhouse regimes), but a forward-looking research agenda can be developed through the application of Quaternary geology to a wide variety of fields that are virtually unexplored. Areas where our expertise in stratigraphy and sedimentology can gain increasing importance using the Quaternary record include the detection of the effects of short-term tectonism and improving seismic hazard assessment.
The Quaternary record is right beneath our feet and represents a resource that could impart profound insight into the interpretation of ancient strata. This talk will highlight the opportunities and challenges in using the well constrained Quaternary stratigraphic record towards a better understanding of stratigraphic architecture.