Engineering

Publication Search Results

Now showing 1 - 3 of 3
  • (2008) Power, M; Marlon, J; Ortiz, N; Bartlein, P; Harrison, Simon; Mayle, F; Ballouche, A; Bradshaw, R; Carcaillet, C; Cordova, C; Mooney, Scott; Moreno, P; Prentice, I; Thonicke, K; Tinner, W; Whitlock, C; Zhang, Yanling; Zhao, Yong; Ali, Amna; Anderson, Richard; Beer, R; Behling, H; Briles, C; Brown, Katherine; Brunelle, A; Bush, M; Camill, P; Chu, G; Clark, J; Colombaroli, D; Connor, Stuart; Daniau, A; Daniels, M; Dodson, John; Doughty, E; Edwards, Meredith; Finsinger, W; Foster, Douglas; Frechette, J; Gaillard, M; Gavin, D; Gobet, E; Haberle, Simon; Hallett, D; Higuera, P; Hope, G; Horn, S; Inoue, J; Kaltenrieder, P; Kennedy, Liz; Kong, Z; Larsen, C; Long, C; Lynch, Jodi; Lynch, E; McGlone, M; Meeks, S; Mensing, S; Meyer, G; Minckley, T; Mohr, J; Nelson, D; New, J; Newnham, R; Noti, R; Oswald, W; Pierce, J; Richard, P; Rowe, C; Goni, M; Shuman, B; Takahara, H; Toney, J; Turney, C; Urrego-Sanchez, D; Umbanhowar, C; Vandergoes, M; Vanniere, B; Vescovi, E
    Journal Article
    Fire activity has varied globally and continuously since the last glacial maximum (LGM) in response to long-term changes in global climate and shorter-term regional changes in climate, vegetation, and human land use. We have synthesized sedimentary charcoal records of biomass burning since the LGM and present global maps showing changes in fire activity for time slices during the past 21,000 years (as differences in charcoal accumulation values compared to pre-industrial). There is strong broad-scale coherence in fire activity after the LGM, but spatial heterogeneity in the signals increases thereafter. In North America, Europe and southern South America, charcoal records indicate less-than-present fire activity during the deglacial period, from 21,000 to ∼11,000 cal yr BP. In contrast, the tropical latitudes of South America and Africa show greater-than-present fire activity from ∼19,000 to ∼17,000 cal yr BP and most sites from Indochina and Australia show greater-than-present fire activity from 16,000 to ∼13,000 cal yr BP. Many sites indicate greater-than-present or near-present activity during the Holocene with the exception of eastern North America and eastern Asia from 8,000 to ∼3,000 cal yr BP, Indonesia and Australia from 11,000 to 4,000 cal yr BP, and southern South America from 6,000 to 3,000 cal yr BP where fire activity was less than present. Regional coherence in the patterns of change in fire activity was evident throughout the post-glacial period. These complex patterns can largely be explained in terms of large-scale climate controls modulated by local changes in vegetation and fuel load.

  • (2021) Alohali, Ruaa Tawfiq A
    Thesis
    The Arabian basin was subject to several tectonic events, including Lower Cambrian Najd rifting, the Carboniferous Hercynian Orogeny, Triassic Zagros rifting, and the Early/Cretaceous and Late/Tertiary Alpine orogenic events. These events reactivated Precambrian basement structures and affected the structural configuration of the overlying Paleozoic cover succession. In addition to a 2D seismic array and several drill well logs, a newly acquired, processed 3D seismic image of the subsurface in part of the basin covering an area of approximately 1051 km2 has been provided to improve the understanding of the regional tectonic evolution associated with these deformation events. In this study, a manual interpretation is presented of six main horizons from the Late Ordovician to the Middle Triassic. Faults and folds were also mapped to further constrain the stratigraphic and structural framework. Collectively, this data is used to build a geological model of the region and develop a timeline of geological events. Results show that a lower Paleozoic sedimentary succession between the Late Silurian to the Early Permian was subject to localised tilting, uplift, and erosion during the Carboniferous Hercynian Orogeny, forming a regional unconformity. Subsequent deposition occurred from the Paleozoic to the Mesozoic, producing a relatively thick, conformable, upper succession. The juxtaposition of the Silurian rocks and Permian formations allows a direct fluid flow between the two intervals. Seismic analysis also indicated two major fault generations. A younger NNW-striking fault set with a component of reverse, east-side-up displacement affected the Lower Triassic succession and is most likely related to the Cretaceous and Tertiary Alpine Events that reactivated the Najd fault system. These fault structures allow vertical migration that could act as conduits to form structural traps. Manual mapping of fault structures in the study area required significant time and effort. To simplify and accelerate the manual faults interpretation in the study area, a fault segmentation method was developed using a Convolutional Neural Network. This method was implemented using the 3D seismic data acquired from the Arabian Basin. The network was trained, validated, and tested with samples that included a seismic cube and fault images that were labelled manually corresponding to the seismic cube. The model successfully identified faults with an accuracy of 96% and an error rate of 0.12 on the training dataset. To achieve a more robust model, the prediction results were further enhanced using postprocessing by linking discontinued segments of the same fault and thus, reducing the number of detected faults. This method improved the accuracy of the prediction results of the proposed model using the test dataset by 77.5%. Additionally, an efficient framework was introduced to correlate the predictions and the ground truth by measuring their average distance value. This technique was also applied to the F3 Netherlands survey, which showed promising results in another region with complex fault geometries. As a result of the automated technique developed here, fault detection and diagnosis were achieved efficiently with structures similar to the trained dataset and has a huge potential in improving exploration targets that are structurally controlled by faults.

  • (2023) Baker, Mackenzie
    Thesis
    The Australian continent provides an excellent canvas to study the impacts of dynamic topography due to the flat nature of the continent. Previous work into Australian studies of biota have mainly focused on climate being the main contributor to biotic distribution and evolution. This study will investigate the influence dynamic topography contributes to this evolution of the landscape and biota through implementing three landscape evolution models (AuM1, AuM2 and AuM3), created using Badlands software. These models will establish the impacts dynamic topography has to the evolution of the Australian landscape and biota over the last 40 million years. All three models possessed the same inputs of elevation, precipitation, sea-level and erodibility regions, however differed in their dynamic topography input. The first of these models (AuM1) involves a best fit model of the Australian continent with a dynamic topography input that was an accurate depiction of the dynamic topography within the Australian continent. The second model acted as a control model, with the subtraction of a dynamic topography input. Lastly the third model (AuM3) involved the input of a varying dynamic topography inconsistent with AuM1. The comparison of these models exhibits that changes to the Australian landscape have taken place. The main finding was the deposition rate of sediment changes between AuM1 and AuM2, where AuM2 possess lower rates of deposition in the northern region. With these lower rates of sediment deposition, there was an accompanying narrower confluence angle of river channels in the northeastern region, indicating a more arid environment for those simulations without dynamic topography (AuM2). With these new findings through the numerical modelling of the Australian continent new constraints to the evolution of the Australian landscape and biota have been gained.