ALBERT

Description: Petroleum systems located at passive continental margins received increasing attention in the last decade mainly because of deep- and ultra‐deep-water hydrocarbon exploration and production. The high risks associated with these settings originate mainly from the poor understanding of inherent geodynamic processes. The new priority program SAMPLE (South Atlantic Margin Processes and Links with onshore Evolution), established by the German Science Foundation in 2009 for a total duration of 6 years, addresses a number of open questions related to continental breakup and post‐breakup evolution of passive continental margins. 27 sub‐projects take advantage of the exceptional conditions of the South Atlantic as a prime “Geo‐archive.” The regional focus is set on the conjugate margins located east of Brazil and Argentina on one side and west of Angola, Namibia and South Africa on the other (Figure 1) as well as on the Walvis Ridge and the present‐day hotspot of Tristan da Cunha. The economic relevance of the program is demonstrated by support from several petroleum companies, but the main goal is research on fundamental processes behind the evolution of passive continental margins.

Description: The Arctic changes rapidly in response to global warming and is expected to change even faster in the future (IPCC 2001, 2007, 2013). Large areas of the shelves and continental slopes bordering the Arctic Ocean are characterized by permafrost and the presence of gas hydrates. Future global warming and potential hydrate dissociation in the Arctic Ocean challenge the slope stability of these areas. This may lead to slope failures. The first, and so far only reported, large-scale slope failure in the Arctic Ocean is the Hinlopen/Yermak Megaslide (HYM), which is located in front of the Hinlopen glacial trough north of Svalbard. During cruise MSM31 onboard the German R/V MARIA S. MERIAN we investigated this giant slope failure and the deeper structure of the Sophia Basin in detail to elucidate the potential causes of the main and following failure events as well as to test existing hypotheses on the generation of this giant submarine landslide. We studied the megaslide and the adjacent so far not failed shelf areas by means of multibeam swath bathymetry, Parasound sediment echo sounder, low- and high-resolution multichannel seismic reflection profiling. The seismic data image bottom-simulating reflectors beneath not failed areas of the slope, as well as a buried gas escape pipe. On the shelf, shallower than the gas hydrate stability zone, we observed widespread gas seepage as flares in the Parasound echo sounder data. These flares rise from a seafloor highly disturbed by iceberg scouring. Therefore, we could not identify pockmarks in the multibeam data. At one location, we sampled a flare by means of a CTD probe close to the seafloor and proofed that the emanating gas has a high methane concentration. The new data indicate that the existence of gas and gas hydrates beneath the shelf north of Svalbard was one key factor causing slope instability in the past and may also cause further slope failures in the future.

Description: The modern polar cryosphere reflects an extreme climate state with profound temperature gradients towards high-latitudes. It developed in association with stepwise Cenozoic cooling, beginning with ephemeral glaciations and the appearance of sea ice in the late middle Eocene. The polar ocean gateways played a pivotal role in changing the polar and global climate, along with declining greenhouse gas levels. The opening of the Drake Passage finalized the oceanographic isolation of Antarctica, some 40 Ma ago. The Arctic Ocean was an isolated basin until the early Miocene when rifting and subsequent sea-floor spreading started between Greenland and Svalbard, initiating the opening of the Fram Strait / Arctic-Atlantic Gateway (AAG). Although this gateway is known to be important in Earth’s past and modern climate, little is known about its Cenozoic development. However, the opening history and AAG’s consecutive widening and deepening must have had a strong impact on circulation and water mass exchange between the Arctic Ocean and the North Atlantic. To study the AAG’s complete history, ocean drilling at two primary sites and one alternate site located between 73°N and 78°N in the Boreas Basin and along the East Greenland continental margin are proposed. These sites will provide unprecedented sedimentary records that will unveil (1) the history of shallow-water exchange between the Arctic Ocean and the North Atlantic, and (2) the development of the AAG to a deep-water connection and its influence on the global climate system. The specific overarching goals of our proposal are to study: (1) the influence of distinct tectonic events in the development of the AAG and the formation of deep water passage on the North Atlantic and Arctic paleoceanography, and (2) the role of the AAG in the climate transition from the Paleogene greenhouse to the Neogene icehouse for the long-term (~50 Ma) climate history of the northern North Atlantic. Getting a continuous record of the Cenozoic sedimentary succession that recorded the evolution of the Arctic-North Atlantic horizontal and vertical motions, and land and water connections will also help better understanding the post-breakup evolution of the NE Atlantic conjugate margins and associated sedimentary basins.

Description: New biostratigraphic zonations, core descriptions, sandstone petrography, facies analysis, and seismic information are compared with published detrital and bedrock geo- and thermochronology to build a Cenozoic paleogeographic reconstruction of the Andean retroarc region of Colombia, encompassing the ancestral Central Cordillera, Middle Magdalena Valley, Eastern Cordillera, and Llanos basin. We identify uplifted sediment source areas, provenance domains, depositional environments, and thickness changes to propose a refined paleogeographic evolution of eastern Colombia. We conclude that Cenozoic evolution of the northernmost Andes includes (1) a period of contractional deformation focused in the Central Cordillera and Middle Magdalena Valley that may have started by the Late Cretaceous, although thermochronological data points to maximum shortening and exhumation during the late Paleocene; (2) a period of slower deformation rates or even tectonic quiescence during the middle Eocene; and (3) a renewed phase of contractional deformation from the late Eocene to the Pleistocene/Holocene expressed in provenance, bedrock thermochronology, and increased subsidence rates in the Llanos foreland. The sedimentary response in the Llanos foreland basin is controlled by source area proximity, exhumation and shortening rates, relationships between accommodation and sediment supply, as well as potential paleoclimate forcing. This new reconstruction changes the picture of Cenozoic basin evolution offered by previous reconstructions, providing an updated chronology of deformation, which is tied to a more precise understanding of basin evolution.

Description: In Colombia, palynology has been widely used as a biostratigraphic tool in oil exploration over the last two decades and, as a result of these efforts, an understanding of the chronostratigraphic range of thousands of palynomorph species is now available. Furthermore, because of their relative resistance to physical and chemical degradation, palynomorphs can often survive several tectonic-erosive cycles, allowing them to be used as unique tracers of long-term sedimentological changes. In this work, we use the palynological record from wells and outcrops in the Llanos foothills and the Llanos basin of Colombia to establish the intensity of Cenozoic reworking and its relationship to the tectonic evolution of the Colombian Andes. Using this approach, we were able to discern several tectonic episodes associated with the uplift of the Eastern Cordillera. We documented three periods of either faster erosion in the hinterland or more widespread areas being eroded in the catchment areas (late Paleocene–early Eocene, early to mid Miocene and Pliocene) and two periods of tectonic quiescence (mid-Eocene and mid–late Miocene). These periods correlate well with the deposition of different elements of the petroleum systems in the Llanos basin of Colombia (seals and reservoirs).

Description: Physical and geochemical characteristics of produced petroleum from the central region of the Llanos basin, Colombia, were analyzed to understand the petroleum charge history and alteration processes. Petroleum properties in the study area are the result of the complex charge history of the oil fields. The amount of gas in fluids is controlled by the migration distance from the late or, possibly, the current generation kitchen located beneath the foothill deformation zone. Gas influx decreases toward the foreland domain, as indicated by lower values of the gas–oil ratio and saturation pressure. The API gravity of the oil samples is mainly controlled by the intensity of biodegradation. Marine-sourced oils accumulated in shallow reservoirs of the foreland prior to the onset of Andean deformation. Those fluids were subjected to different levels of biodegradation, depending on the time they remained at reservoir temperatures lower than 80°C (176°F) and before being buried to their maximum depth. Geochemical data suggest multiple charge pulses from different source kitchens of two main types of source rocks, as well as different biodegradation levels. The proposed petroleum charge and alteration model allows prediction of the temperature history of a reservoir and the most likely physical properties of the petroleum at a specific location. The model can be used as an exploration tool to assess the risk of charge prior to drilling in unexplored areas of the basin.

Description: The Llanos basin, located in the eastern region of Colombia, northwestern South America, is an Andean foreland basin between the Eastern Cordillera (Colombian Andes) and the Guyana Precambrian shield. The basin is the latest stage of a complex multiphase evolution that began in the Paleozoic at the latest. A Paleozoic–Pleistocene basin evolution model is presented based on a regional, two-dimensional, industry seismic data set and well-log observations for the southern part of the basin. Five tectono-stratigraphic sequences were identified: (1) lower Paleozoic depocenters preserved along inverted Neoproterozoic basement blocks; (2) an upper Paleozoic marine sequence folded and faulted in the late Paleozoic during assembly of Pangea; (3) Upper Cretaceous–Paleocene shallow marine sediments deposited in a distal foreland basin related to uplift of the Western and Central Cordilleras of Colombia, the sequence pinches out against a Paleozoic hinge or foreland bulge area; (4) an Eocene–Miocene foreland basin related to uplift of the Eastern Cordillera resulting in a wedge geometry; and (5) Pliocene–Pleistocene fluvial deltaic rocks overfilling the foreland basin. Reactivation of Paleozoic structures occurs at the top of this sequence with the development of anticlinal structures. Present-day stress fields indicate that subduction of the Nazca plate beneath South America may be responsible for reactivation of Paleozoic structures. Inversion of north–south structures with the Neoproterozoic basement is interpreted to be responsible for the Paleozoic and Pleistocene deformation, whereas Cenozoic deformation is related to the two main stages of foreland development of the basin. To the east, where the Paleoproterozoic basement is present, no deformation is interpreted.

Description: In the present study, stratigraphic data from cores and outcrop sections are integrated with data on thermal maturity, organic facies, and thermochronometric information to reconstruct the tectonic and associated petroleum system evolution of the eastern foothills thrust belt along the Colombian Eastern Cordillera, one of the most prolific hydrocarbon provinces in northern South America. Sedimentary and tectonic burial of the foreland autochthon caused maturation of the Coniacian to Santonian shallow marine Chipaque Formation, resulting in successive and diachronous episodes of hydrocarbon migration and trapping. One-dimensional and two-dimensional maturation modeling indicates that oil generation from the Chipaque Formation began at the Paleocene-Eocene boundary (55 Ma) in the southern parts of what is now the Eastern Cordillera and progressed to the north. By the late Oligocene, tectonic inversion of the Eastern Cordillera exhumed most of these kitchens, terminating the oil generation from the Chipaque Formation. Kitchens migrated northward and eastward during the Oligocene and early Miocene. Because of the absence or subsequent erosion of traps, it is likely that the southernmost source rocks expelled most of their oil without any appreciable accumulation. Our modeling indicates that there were two important kitchens during the Cenozoic. The larger of the two was located in the present-day Eastern Cordillera, and it was most productive in the late Eocene–early Oligocene. The second kitchen, which generated oil throughout the Neogene, was located in the foredeep of the Llanos basin, adjacent to the mountain front. Considerable amounts of oil from this recent pulse have accumulated in both deep and shallow reservoirs along the eastern foothills. The modeled reservoir charge history also explains the substantial biodegradation of oils in reservoirs that are today much too deep to support the process. Biodegradation must have occurred when the reservoirs were shallower and at cooler temperatures, and they remained active until the reservoirs were buried to depths where temperatures were high enough to prevent further bacterial activity.

Description: In this paper, we demonstrate a workflow for constructing kinematic restorations in complex foothill areas devoid of growth strata and other indicators for the chronology of deformation. Our initial reconstructions utilize thermochronometric data, a well-documented structural geometry, and a first-order conversion of exhumation rates into tectonic rates. We then utilize models obtained from the new in-house–developed software FetKin to build a first version of the thermokinematic restoration. The FetKin approach is geared primarily toward testing and further calibration and refinement of the kinematic restoration, based on the extent to which the model result agrees with thermochronometric data from the study area in the form of both discrete ages and inverse-modeled time–temperature envelopes. This analysis also provides rates of shortening and time–temperature paths throughout the model space that can be used to make first-order predictions of when different source rocks entered the oil window. These capabilities are demonstrated in a pilot case study along a cross section in the Colombian Eastern Cordillera. The improved confidence in the reconstruction that this technique provides allows us to show increasing shortening rates in this part of the Andes during the Neogene reaching up to 5 mm/yr (0.20 in./yr) by the Pliocene, and constrain the timing of generation from the most important oil kitchens for the Eastern Cordillera-Llanos basin petroleum system. This approach, therefore, proves to be a useful method for creating high-resolution and high-fidelity kinematic restorations.