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Yngve Kristoffersen - One of the best experts on this subject based on the ideXlab platform.
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the nature of the acoustic basement on Mendeleev and northwestern alpha ridges arctic ocean
Tectonophysics, 2012Co-Authors: Vibeke Bruvoll, Bernard Coakley, John R Hopper, Yngve Kristoffersen, Sverre Planke, Aleksandre KandilarovAbstract:Abstract The Alpha-Mendeleev ridge complex, over 1500 km long and 250–400 km wide, is the largest submarine structure in the Arctic Ocean basin. Its origin is unknown, but often inferred to represent a large igneous province where domains of continental crust may also be a possibility. We investigate the basement geology of part of this large scale feature using 1100 km of multichannel seismic reflection data, sonobuoy recordings and marine gravity data acquired in 2005 from USCG icebreaker Healy. The sonobuoy results show top and intra-acoustic basement velocities in the range of 2.3–4.0 km/s and the seismic reflection attributes define three main acoustic facies: 1) continuous high amplitude reflections often with abrupt breaks, 3) weak wedge geometry and 3) segmented, disrupted to chaotic reflections. The acoustic characteristics and seismic velocities compare more closely with basement on Ontong Java Plateau than normal ocean crust or wedges of seaward dipping reflections at volcanic margins. The acoustic facies are interpreted to represent basalt flows and sills capping voluminous tuff deposits and possible sediments. At least two volcanic centres are identified. The upper volcanic carapace on the surveyed part of Mendeleev and northwestern Alpha ridges was emplaced during a brief igneous episode no later than Campanian (80 Ma) and most likely part of wider Late Cretaceous circum Arctic volcanism. The horst and graben morphology on Mendeleev Ridge is largely a result of post-emplacement faulting where a number of the major extensional faults remained active until a late Miocene intrusive event.
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bathymetry controlled source seismic and gravity observations of the Mendeleev ridge implications for ridge structure origin and regional tectonics
Geophysical Journal International, 2010Co-Authors: Dayton Dove, Bernard Coakley, John R Hopper, Yngve KristoffersenAbstract:Multichannel seismic (MCS), seismic refraction, and gravity data collected down the flank of the Chukchi Plateau, but predominantly over the Mendeleev Ridge have been processed and interpreted to describe the crustal style of the ridge, as well as the structural history. These results provide constraints on the origin of the ridge, and the tectonic evolution of the Amerasian Basin. MCS images reveal two primary sediment sequences separated by an unconformity that persists across the entire Mendeleev Ridge. The basement and lower sediment sequence exhibit pervasive normal faulting. The upper sequence is laterally conformable and not effected by faulting, thus the regional unconformity dividing the two sequences is interpreted to mark the end of extensional deformation. Modeling of sonobuoy seismic refraction data reveals upper crustal P-wave velocities ranging from 3.5 to 6.4 km s−1 approximately 5 km into the basement. The velocity structure of the Mendeleev Ridge is consistent with either a volcanic rifted continental margin, or an oceanic plateau origin. Observed gravity anomalies over the ridge are reproduced by a model consisting of bathymetry, sediment and basement horizons from the MCS data and a single crustal layer of 2.86 g cm−3. This result is consistent with homogeneous, mafic crust. The similar velocity and density structures of the Mendeleev and Alpha ridges is consistent with a model where the two ridges are contiguous and share a common geological origin. Gravity modelling over the transition between the Chukchi Plateau and the Mendeleev Ridge suggests the two features have differing compositions and distinct emplacement histories. Three tectonic models are presented for the origin of the Alpha Mendeleev Ridge (AMR) that satisfy constraints set by this and previous studies: (1) a rifted volcanic continental margin, (2) an oceanic plateau formed at a spreading centre—perpendicular to the AMR and (3) an oceanic plateau formed at a spreading centre—parallel to the AMR.
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Hemipelagic deposits on the Mendeleev and northwestern Alpha submarine Ridges in the Arctic Ocean: acoustic stratigraphy, depositional environment and an inter-ridge correlation calibrated by the ACEX results
Marine Geophysical Researches, 2010Co-Authors: Vibeke Bruvoll, Yngve Kristoffersen, Bernard J. Coakley, John R HopperAbstract:The first high resolution multichannel seismic data from the Mendeleev and Alpha Ridges in the Arctic Ocean have been used to investigate the depositional history, and compare acoustic stratigraphies of the three main sub-marine ridges (Mendeleev, Alpha and Lomonosov) in the polar ocean. Acoustic basement on the Mendeleev Ridge is covered by a ~0.6–0.8 s thick sediment drape over highs and up to 1.8 s within grabens. A pronounced angular discordance at 0.18–0.23 s below the seafloor along the middle to upper slopes divides the succession into an upper, undisturbed, uniformly thick, hemipelagic drape (Unit M1) and a partially truncated lower unit (Unit M2) characterized by strong reflection bands. Unit M2 is thicker in intra-ridge grabens and includes three sub-units with abundant debris flows in the uppermost subunit (M2a). The discordance between Units M1 and M2 most likely relates to instability along the middle to upper slopes and mass wasting, triggered by tectonic activity. The scars were further smoothed by bottom current erosion. We observe comparable acoustic stratigraphy and discordant relationships on the investigated northwestern part of Alpha Ridge. Similarly, on the central Lomonosov Ridge, Paleocene and younger sediments sampled by scientific drilling include an uppermost ~0.2 s thick drape overlying, highly reflective deposits with an angular unconformity confined to the upper slope on both sides of the ridge. Sediment instability on the three main ridges was most likely generated by a brief phase of tectonic activity (~14.5–22 Ma), coinciding with enhanced bottom circulation. These events are coeval with the initial opening of the Fram Strait. The age of the oldest sediments above acoustic basement on the Mendeleev- and west-central Alpha Ridges is estimated to be 70–75 Ma.
John R Hopper - One of the best experts on this subject based on the ideXlab platform.
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the nature of the acoustic basement on Mendeleev and northwestern alpha ridges arctic ocean
Tectonophysics, 2012Co-Authors: Vibeke Bruvoll, Bernard Coakley, John R Hopper, Yngve Kristoffersen, Sverre Planke, Aleksandre KandilarovAbstract:Abstract The Alpha-Mendeleev ridge complex, over 1500 km long and 250–400 km wide, is the largest submarine structure in the Arctic Ocean basin. Its origin is unknown, but often inferred to represent a large igneous province where domains of continental crust may also be a possibility. We investigate the basement geology of part of this large scale feature using 1100 km of multichannel seismic reflection data, sonobuoy recordings and marine gravity data acquired in 2005 from USCG icebreaker Healy. The sonobuoy results show top and intra-acoustic basement velocities in the range of 2.3–4.0 km/s and the seismic reflection attributes define three main acoustic facies: 1) continuous high amplitude reflections often with abrupt breaks, 3) weak wedge geometry and 3) segmented, disrupted to chaotic reflections. The acoustic characteristics and seismic velocities compare more closely with basement on Ontong Java Plateau than normal ocean crust or wedges of seaward dipping reflections at volcanic margins. The acoustic facies are interpreted to represent basalt flows and sills capping voluminous tuff deposits and possible sediments. At least two volcanic centres are identified. The upper volcanic carapace on the surveyed part of Mendeleev and northwestern Alpha ridges was emplaced during a brief igneous episode no later than Campanian (80 Ma) and most likely part of wider Late Cretaceous circum Arctic volcanism. The horst and graben morphology on Mendeleev Ridge is largely a result of post-emplacement faulting where a number of the major extensional faults remained active until a late Miocene intrusive event.
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bathymetry controlled source seismic and gravity observations of the Mendeleev ridge implications for ridge structure origin and regional tectonics
Geophysical Journal International, 2010Co-Authors: Dayton Dove, Bernard Coakley, John R Hopper, Yngve KristoffersenAbstract:Multichannel seismic (MCS), seismic refraction, and gravity data collected down the flank of the Chukchi Plateau, but predominantly over the Mendeleev Ridge have been processed and interpreted to describe the crustal style of the ridge, as well as the structural history. These results provide constraints on the origin of the ridge, and the tectonic evolution of the Amerasian Basin. MCS images reveal two primary sediment sequences separated by an unconformity that persists across the entire Mendeleev Ridge. The basement and lower sediment sequence exhibit pervasive normal faulting. The upper sequence is laterally conformable and not effected by faulting, thus the regional unconformity dividing the two sequences is interpreted to mark the end of extensional deformation. Modeling of sonobuoy seismic refraction data reveals upper crustal P-wave velocities ranging from 3.5 to 6.4 km s−1 approximately 5 km into the basement. The velocity structure of the Mendeleev Ridge is consistent with either a volcanic rifted continental margin, or an oceanic plateau origin. Observed gravity anomalies over the ridge are reproduced by a model consisting of bathymetry, sediment and basement horizons from the MCS data and a single crustal layer of 2.86 g cm−3. This result is consistent with homogeneous, mafic crust. The similar velocity and density structures of the Mendeleev and Alpha ridges is consistent with a model where the two ridges are contiguous and share a common geological origin. Gravity modelling over the transition between the Chukchi Plateau and the Mendeleev Ridge suggests the two features have differing compositions and distinct emplacement histories. Three tectonic models are presented for the origin of the Alpha Mendeleev Ridge (AMR) that satisfy constraints set by this and previous studies: (1) a rifted volcanic continental margin, (2) an oceanic plateau formed at a spreading centre—perpendicular to the AMR and (3) an oceanic plateau formed at a spreading centre—parallel to the AMR.
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Hemipelagic deposits on the Mendeleev and northwestern Alpha submarine Ridges in the Arctic Ocean: acoustic stratigraphy, depositional environment and an inter-ridge correlation calibrated by the ACEX results
Marine Geophysical Researches, 2010Co-Authors: Vibeke Bruvoll, Yngve Kristoffersen, Bernard J. Coakley, John R HopperAbstract:The first high resolution multichannel seismic data from the Mendeleev and Alpha Ridges in the Arctic Ocean have been used to investigate the depositional history, and compare acoustic stratigraphies of the three main sub-marine ridges (Mendeleev, Alpha and Lomonosov) in the polar ocean. Acoustic basement on the Mendeleev Ridge is covered by a ~0.6–0.8 s thick sediment drape over highs and up to 1.8 s within grabens. A pronounced angular discordance at 0.18–0.23 s below the seafloor along the middle to upper slopes divides the succession into an upper, undisturbed, uniformly thick, hemipelagic drape (Unit M1) and a partially truncated lower unit (Unit M2) characterized by strong reflection bands. Unit M2 is thicker in intra-ridge grabens and includes three sub-units with abundant debris flows in the uppermost subunit (M2a). The discordance between Units M1 and M2 most likely relates to instability along the middle to upper slopes and mass wasting, triggered by tectonic activity. The scars were further smoothed by bottom current erosion. We observe comparable acoustic stratigraphy and discordant relationships on the investigated northwestern part of Alpha Ridge. Similarly, on the central Lomonosov Ridge, Paleocene and younger sediments sampled by scientific drilling include an uppermost ~0.2 s thick drape overlying, highly reflective deposits with an angular unconformity confined to the upper slope on both sides of the ridge. Sediment instability on the three main ridges was most likely generated by a brief phase of tectonic activity (~14.5–22 Ma), coinciding with enhanced bottom circulation. These events are coeval with the initial opening of the Fram Strait. The age of the oldest sediments above acoustic basement on the Mendeleev- and west-central Alpha Ridges is estimated to be 70–75 Ma.
S G Skolotnev - One of the best experts on this subject based on the ideXlab platform.
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New data concerning the ferromanganese crusts of the Mendeleev rise (Arctic Ocean)
Доклады Академии наук, 2019Co-Authors: E S Bazilevskaya, S G SkolotnevAbstract:The results of study of Fe-Mn crusts from the Mendeleev Rise in the Arctic Ocean in 2016 sampled with manipulators from a submarine are presented. Concentrations of Fe, Mn, Co, Ni, Zn, Cu, Cr and Pb are measured in collected Fe-Mn crusts. The variations in the content of these elements are determined by the chemical properties of the elements, the height of the underwater topography, the composition of the underlying substrate and the presence of bottom silt.
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fossils from seabed bedrocks implications for the nature of the acoustic basement of the Mendeleev rise arctic ocean
Marine Geology, 2019Co-Authors: S G Skolotnev, G N Aleksandrova, T N Isakova, Tatyana Tolmacheva, Alena Kurilenko, Elena Raevskaya, Sergey V Rozhnov, Evgeny Petrov, Andrey KorniychukAbstract:Abstract The geological information on the structure of the Mendeleev Rise in the Arctic Ocean is scarce due to inaccessibility of this offshore area; therefore its origin is still disputable. Two expeditions of the multi-year programme of deepwater research are devoted to solving this problem. The programme is based on integrated seafloor studies using a research submarine for recovering bedrock samples from seafloor outcrops under subglacial conditions. Sampling was performed in three polygons in the southwestern, central and northern parts of the Mendeleev Rise, where according to seismic data, an acoustic basement crops out at the seabed. Sedimentary and igneous rocks were sampled, with similar rock types in all three of the polygons. The fossils were extracted from sedimentary rocks. The detailed study of crinoids, conodonts, acritarchs, brachiopods, foraminifers, dinocysts, spores and pollen was carried out. Obtained data allowed the dating of 13 samples. Among sedimentary rocks exposed on steep slopes of the Mendeleev Rise , stratigraphic units of three ages were identified: Late Ordovician-Silurian, Middle-Late Devonian and Early Cretaceous. The Upper Ordovician-Silurian rock association mainly occurs in lower parts of the sampled slopes and consists of alternating dolomites, quartzose sandstones and limestones. Carbonate rocks with clastic components similar to those in quartzose sandstones as well as quartzose sandstones with dolomite cement were encountered. Partly dolomitised varieties were observed among limestones; the same spectrum of bioclasts is found in dolomites and limestones. The Middle-Upper Devonian (upper Givetian – Famennian) rock association occur s mainly in upper parts of the slopes and consists of alternating limestones and sandstones. The Lower Cretaceous (Barremian-Aptian) sandstones occur in the upper part of the slope of the Trukshin Seamount (the north of the Mendeleev Rise). New geological data demonstrates that lower and middle Paleozoic rocks of the Mendeleev Rise were deposited in the shallow-water marine environments of the epicontinental basin. Paleozoic deposits form the upper part of the acoustic basement of the Mendeleev Rise. Overlaying Lower Cretaceous sandstones are the basal layer of the stratified Mesozoic-Cenozoic sedimentary cover of the Mendeleev Rise.
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fe mn nodules of the Mendeleev ridge arctic ocean
Doklady Earth Sciences, 2015Co-Authors: E S Bazilevskaya, S G SkolotnevAbstract:The results of study of Fe–Mn crusts from the Mendeleev Ridge in the Arctic Ocean sampled with manipulators from a submarine are presented. In almost all the samples, the ore phase is significantly enriched in some valuable trace elements (Ni, Co, Cu, etc.), the contents of which exceed those in ores from the pelagic zones of other oceans. The high ore potential of the Arctic pelagic zone is stated and substantiated.
Wilfried Jokat - One of the best experts on this subject based on the ideXlab platform.
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THE SEDIMENTARY STRUCTURE BETWEEN THE Mendeleev AND LOMONOSOV RIDGES
2020Co-Authors: Michele Ickrath, Wilfried JokatAbstract:During the RV Polarstern cruise ARK-XXIII-3 in summer of 2008, a nearly 1000 km long seismic transect along 81° N including the Amundsen Basin, Lomonosov Ridge, Makarov Basin, Mendeleev Ridge and Mendeleev Basin was acquired. The objective was to understand the tectonic evolution of the Makarov Basin in relation to the evolution of the ridge system in the Amerasia Basin. The survey set-up included a300 m streamer and a 32 ltr airgun cluster. Because of ice conditions, gaps remained between the profiles.In addition to reflection seismic data with a 300 m streamer, 8 sonobuoys were deployed along the profiles to better resolve the seismic velocities in the sedimentary column. Initial results show high velocities near the surface in the Makarov Basin with values around 2.6 2.9 km/s. The flat-lying well-stratified units are most likely of Cenozoic age. Towards the ridges, the seismic velocities decrease to 2.2 2.4 km/s. The seismic velocities of the acoustic basement vary from >5.0 km/s in the centralbasin (5.5 s TWT) to 4.1 km/s (3.5 4 s TWT) close to the Mendeleev Ridge. The entire transect is dominated by a partly erosional unconformity, which may mark the break-up of the Lomonosov Ridge from the Siberian/Barents shelves. It divides the sediments into a Cenozoic and Mesozoic portion. First results of the data analysis will be shown.
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Current geoscientific knowledge on the High Arctic submarine Alpha-Mendeleev complex
2020Co-Authors: Wilfried Jokat, R. MüheAbstract:Today Alpha-Mendeleev Ridge is the largest single submarine feature in the Arctic Ocean, which geological origin is still unknown. A better understanding of the evolution of the ridge complex in relation to the opening of the Canada Basin would have profound consequences for Arctic geodynamic models. Currently models in which Alpha Ridge represents a former spreading centre or "hot spot" trail are favoured. In this contribution the state of knowledge will be reviewed.The ridge was discovered by the US ice station Alpha during its drift in the years 1957-1958, which acquired the first information on the ridges topography and sedimentary thickness. The largest single-channel seismic data set was gathered during the drift of the US ice station T-3 from February 1967 to June 1970. The width of Alpha Ridge ranges from 250 to 800 km. In bathymetric cross sections it is roughly symmetrical with greatest elevation at the centre. The existing single channel seismic reflection lines acquired from ice stations Alpha, T-3 and CESAR and ship based seismic experiments show that Alpha-Mendeleev Ridge is mainly covered by a sedimentary sequence, which can reach up to 1000 m in thickness. Along most of the profiles the sediments lie conformably on the basement. Deep seismic experiments of Canadian and Russian researchers indicate that the crust beneath the ridge has a thickness well above 30 km, and high seismic velocities above 7.0 km/s are present at lower crustal levels.The most important and complete geophysical data sets in that area are aeromagnetic and aerogravity data acquired by US and Russian researchers. The magnetic data across the Alpha Ridge indicate the presence of mostly irregular magnetic anomalies up to 2000 nT. No clear evidence of magnetic seafloor spreading anomalies has been obtained. Based on the existing geophysical data various researchers suggested that the ridge must have been formed during the Cretaceous positive polarity chron from 124 to 83 Ma, if the irregular magnetic anomalies are due to oceanic basalts. At three locations Cretaceous and Early Cenozoic sediments were recovered from western part of Alpha-Mendeleev Ridge. Two volcanic rock samples were dredged from the Alpha-Mendeleev Ridge. One of them could be dated to 83 Ma. So far, all existing geoscientific data support a formation of this complex in Cretaceous times. However, details on the responsible processes and the plate movements during this period are rather hypothetical.
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Seismostratigraphy of the Eastern Makarov Basin and Adjacent Lomonosov Ridge and Mendeleev Ridge
2015Co-Authors: Estella Weigelt, Wilfried JokatAbstract:The contribution presents a high-resolution seismic reflection section collected along a transect at 81°N from the Mendeleev Ridge, across the Makarov Basin onto the Lomonosov Ridge. The slopes of both ridges bordering the Makarov Basin are compared concerning their surface of acoustic basement and configuration of seismic units to research tectonic and depositional processes. Age control for the sedimentary units was acquired via links to seismic lines and drill site data of the Canada Basin, the Lomonosov Ridge, and the adjacent Laptev Shelf. A tie point for dating is a pronounced sequence of high-amplitude reflectors, which is the most striking feature in the Siberian part of the Arctic Ocean. The top of the reflector band is suggested to mark the end of Oligocene, and its base likely corresponds to the base of Eocene (56 Ma). Seismic units below the high-amplitude reflector sequence show a similar configuration on the slopes of the Lomonosov and Mendeleev Ridges. The layers onlap on the slopes of the ridges and fill the basement topography in the center of the Makarov Basin. That indicates a sedimentary transport from the ridges and also the Laptev Shelf into the Makarov Basin formed before Eocene times. In contrast, seismic units above high-amplitude reflector sequence, and consequently younger than 23 Ma show distinct differences in reflector configuration between the Lomonosov and Mendeleev Ridges. The basement surface of the Mendeleev Ridge rises in several steps from the Makarov Basin with an angle of slope between 0.2 and 1.4 °. Here, sedimentary layers onlap or merge on the western slope of the Ridge and show numerous traces of slumping. Further the layers slightly downgrade from the Mendeleev Ridge westwards towards a basement heigth in the center of the Makarov Basin. In contrast the slopes of the Lomonosov Ridge towards the Makarov Basin are less steep (< 0.5°) and the sedimentary layers drape with almost constant thickness the flanks and crest of the ridge indicating a pelagic deposition realm at least since the Middle Eocene.
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seismic transect across the lomonosov and Mendeleev ridges constraints on the geological evolution of the amerasia basin arctic ocean
Geophysical Research Letters, 2013Co-Authors: Wilfried Jokat, Michele Ickrath, John OconnorAbstract:We report on seismic and petrological data that provide new constraints on the geological evolution of the Amerasia Basin. A seismic reflection transect across theMakarov Basin, located between the Mendeleev and Lomonosov Ridges, shows a complete undisturbed sedimentary section of Mesozoic/Cenozoic age. In contrast to the Mendeleev Ridge, the margin of the Lomonosov Ridge is wide and shows horst and graben structures. We suggest that the Mendeleev Ridge is most likely volcanic in origin and support this finding with a 40Ar/39Ar isotopic age for a tholeiitic basalt sampled from the central Alpha/Mendeleev Ridge. Seismic reflection data for the Makarov Basin show no evidence of compressional features, consistent with the Lomonosov Ridge moving as a microplate in the Cenozoic. We propose that the Amerasia Basin moved as a single tectonic plate during the opening of the Eurasia Basin
Aleksandre Kandilarov - One of the best experts on this subject based on the ideXlab platform.
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the nature of the acoustic basement on Mendeleev and northwestern alpha ridges arctic ocean
Tectonophysics, 2012Co-Authors: Vibeke Bruvoll, Bernard Coakley, John R Hopper, Yngve Kristoffersen, Sverre Planke, Aleksandre KandilarovAbstract:Abstract The Alpha-Mendeleev ridge complex, over 1500 km long and 250–400 km wide, is the largest submarine structure in the Arctic Ocean basin. Its origin is unknown, but often inferred to represent a large igneous province where domains of continental crust may also be a possibility. We investigate the basement geology of part of this large scale feature using 1100 km of multichannel seismic reflection data, sonobuoy recordings and marine gravity data acquired in 2005 from USCG icebreaker Healy. The sonobuoy results show top and intra-acoustic basement velocities in the range of 2.3–4.0 km/s and the seismic reflection attributes define three main acoustic facies: 1) continuous high amplitude reflections often with abrupt breaks, 3) weak wedge geometry and 3) segmented, disrupted to chaotic reflections. The acoustic characteristics and seismic velocities compare more closely with basement on Ontong Java Plateau than normal ocean crust or wedges of seaward dipping reflections at volcanic margins. The acoustic facies are interpreted to represent basalt flows and sills capping voluminous tuff deposits and possible sediments. At least two volcanic centres are identified. The upper volcanic carapace on the surveyed part of Mendeleev and northwestern Alpha ridges was emplaced during a brief igneous episode no later than Campanian (80 Ma) and most likely part of wider Late Cretaceous circum Arctic volcanism. The horst and graben morphology on Mendeleev Ridge is largely a result of post-emplacement faulting where a number of the major extensional faults remained active until a late Miocene intrusive event.