Since the first reconstruction of the supercontinent Pangaea, key advances in plate tectonic reconstructions have been made [1][2][3][4][5][6] . Although the movement of tectonic plates since the start of the mid-Cretaceous period (∼100 million years (Myr) ago) is relatively well understood 1,2 , the longitudinal position of plates before this period is not constrained at all. Here, we use a global mantle tomography model 7 to estimate the longitude of past oceanic subduction zones. We identify 28 remnants of oceanic plates that were subducted into the lower mantle and link these to the mountain building zones from which they are likely to have originated. Assuming that these remnants sank vertically through the mantle, we reconstruct the longitude at which they were subducted. Our estimates for the location of the subduction zones are offset by up to 18• compared with plate tectonic reconstructions for the corresponding period. We did not detect oceanic plate remnants from the Carboniferous period (∼300-360 Myr ago), or before, suggesting that the tomographic visibility of subduction is limited to the past 300 Myr.Since the first qualitative plate reconstruction of the supercontinent Pangaea was determined by fitting palaeoclimatic belts and modern continental margins, key advances in plate reconstructions have been made with the development and use of palaeomagnetic apparent polar wander paths, ocean floor magnetic anomalies and hotspot reference frames 1,2 , leading to global plate tectonic reconstructions 3,5,6 . Absolute plate motion models have often been based on assumed hotspot fixity and are well constrained only up to the Cretaceous period owing to the lack of any preserved older oceanic hotspot tracks 1,2 . These, and other models, offer no control on absolute palaeolongitude before the Cretaceous.Seismic tomography studies of the mantle have allowed for increasingly detailed correlations between deep mantle structure, mostly focused on presumed remnants of subducted plates and plate tectonic evolution [8][9][10][11][12][13][14][15][16] . This, however, has not led to strong constraints on absolute plate motion. Recently, correlations between deep, presumably hot and dense mantle heterogeneities at the core-mantle boundary and large igneous provinces were obtained from a plate reconstruction 3,4 , leading to possible predictions of absolute palaeolongitude for the entire Phanerozoic eon 17 . This reconstruction model, however, assumes zero longitude motion for Africa before the Cretaceous.Here, independently of any reconstruction model, we carry out a global interpretation of positive seismic anomalies in the lower mantle based on the assumptions that these reflect relatively
The Southwest Pacific region is tectonically complex and is home to numerous fossil and active subduction zones. At the Earth's surface, there remains a geological controversy regarding the polarity and continuity of fossil subduction zones in New Zealand and New Caledonia, the origin of obducted ophiolites, the presence of high-pressure metamorphism, the occurrence of widespread Cenozoic magmatism, and the potential disappearance of one or more ocean basins. This controversy can be solved by looking at the lower mantle rather then at the Earth's surface. New P-wave and S-wave mantle tomography models from the Southwest Pacific are presented, which identify a previously unrecognized lower-mantle high-velocity anomaly that cannot be linked to Pacific subduction. The anomaly is located below the Tasman Sea at~1100 km depth, strikes NW-SE and is~2200 km by 600-900 km in lateral extent. By combining relative and absolute plate motions it is demonstrated that when the geological structures at the surface are reinterpreted as a single northeast-dipping 2500-km middle Cenozoic subduction zone (the so-called New Caledonia subduction zone) the lower mantle anomaly can be accounted for, as it is found at the predicted location and depth. Discovery of the lower mantle slab anomaly thereby solves a long-standing geological controversy in the New Zealand-New Caledonia region. Finally, reconstructions and analytical calculations predict a lower mantle slab sinking velocity of~1.5 cm/yr and a lower mantle viscosity of~10 22 Pa•s.
S U M M A R YThe main aim of this study is to create a data set of accurate absolute arrival times for stations in Europe which do not report to the International Seismological Centre (ISC). Waveforms were obtained from data centres and temporary experiments and a semi-automatic picking method was applied to determine absolute arrival times for P and S phases. 85 000 arrival times were picked whose distribution of residuals shows generally low standard deviations on the order of 0.5-0.7 s. Furthermore, mean teleseismic station residuals reflect the properties of the underlying crust and uppermost mantle. Comparison to ISC data for matching event-stationphase combinations also confirms the good quality of the new absolute arrival time picks. Most importantly, this data set complements the ISC data as it fills regional data coverage gaps in Europe.Arrival times are routinely reported by many seismological networks to the International Seismological Centre (ISC), resulting in bulletins of millions of arrival times since 1964. Clearly, a wealth of information can be gained from these data regarding the Earth's interior for example by application of traveltime tomography. However, the reporting stations are not distributed equally over the globe therefore leaving gaps, in particular, in the oceans and stable cratonic regions. Furthermore, the quality of these data, which are mostly handpicked, varies greatly .Besides stations included in arrival time bulletins, a large number of seismic stations exist whose waveforms are not used routinely but are sent to data centres for digital storage. For many events included in these waveforms, arrival times were either not picked at all or only with limitations (e.g. a restricted period in time or limited epicentral distance range).Another valuable source of data is provided by temporary experiments. To fill the geographical gaps, many regional experiments were carried out during the last 15-20 yr where spatially dense temporary networks were placed in the field for several months. Often, arrival times for events registered at those arrays were only picked relatively. That means, not the arrival time of a phase onset was determined but the arrival time of the first maximum or minimum after the onset. This procedure has the advantage that observational errors due to high noise levels can be reduced but as a major disadvantage, * Now at: Chevron Energy Technology Company, Houston, TX, USA. arrival times are only obtained with respect to the unknown mean network arrival time for a specific event. Therefore, they cannot be used for event relocation or to obtain absolute velocity information on the crust and mantle below the array. Consequently, obtaining absolute arrival times for events recorded at such stations which do not report arrival times to the ISC can provide new detailed information for high-resolution traveltime tomography.Besides using additional stations, the picks should also be of a consistent good quality as erroneous picks will affect or overprint velocity structur...
Seismic data are an important source of information to guide and constrain reservoir modeling as it samples the subsurface in 3D away from wells. Seismic interpretations are used to constrain the structure of reservoir models. Different seismic attributes can support the identification and definition of stratigraphic features, and seismic inversion products can help constrain the rock properties. Different methods exist for integration of seismic data in the modeling process. Here, we present two new methods. The first method constrains facies definition and modeling with seismic data through a geobody earth modeling approach. The second method updates existing facies models with new seismic data using a Bayesian approach. Both methods are applied to a case study with good quality seismic data. The results show that the reservoir model becomes more consistent with the observed field seismic data when these fast and repeatable methods are applied (compared to not integrating seismic constraints or using time-intensive manual integration approaches), thus enabling more robust reservoir models and forecasts.
Computational stratigraphy provides a method to model depositional and stratigraphic processes on a grain size scale while honoring physics-based flow dynamics. Using rock-physics equations and assumptions, these computational stratigraphy models can be converted to rock properties such as velocity and density. The rock-physics properties are in turn used to generate synthetic seismic data, which allow studying the seismic expression of stratigraphic features on different scales. These models and their application to existing hydrocarbon reservoirs can provide new insight into connectivity and other characteristics of subsurface reservoirs that are not provided by traditional reservoir-modeling approaches.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.