Journal articles: 'Continental margins'

1

Vangone, Adriano, and Carlo Doglioni. "Asymmetric Atlantic continental margins." Geoscience Frontiers 12, no. 5 (2021): 101205. http://dx.doi.org/10.1016/j.gsf.2021.101205.

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Bosellini, Alfonso. "East Africa continental margins." Geology 14, no. 1 (1986): 76. http://dx.doi.org/10.1130/0091-7613(1986)14<76:eacm>2.0.co;2.

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3

Katsouros, Mary Hope. "NRC Continental Margins Workshop." Eos, Transactions American Geophysical Union 69, no. 43 (1988): 978. http://dx.doi.org/10.1029/88eo01162.

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4

Mutter, John. "Margins: A new conceptual approach to continental margin research." Eos, Transactions American Geophysical Union 71, no. 18 (1990): 679. http://dx.doi.org/10.1029/90eo00167.

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Pettinga, Luke A., and Zane R. Jobe. "How submarine channels (re)shape continental margins." Journal of Sedimentary Research 90, no. 11 (2020): 1581–600. http://dx.doi.org/10.2110/jsr.2020.72.

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ABSTRACT Submarine landscapes, like their terrestrial counterparts, are sculpted by autogenic sedimentary processes toward morphologies at equilibrium with their allogenic controls. While submarine channels and nearby, inter-channel continental-margin areas share boundary conditions (e.g., terrestrial sediment supply, tectonic deformation), there are significant differences between the style, recurrence, and magnitude of their respective autogenic sedimentary processes. We predict that these process-based differences affect the rates of geomorphic change and equilibrium (i.e., graded) morphologies of submarine-channel and continental-margin longitudinal profiles. To gain insight into this proposed relationship, we document, classify (using machine learning), and analyze longitudinal profiles from 50 siliciclastic continental margins and associated submarine channels which represent a range of sediment-supply regimes and tectonic settings. These profiles tend to evolve toward smooth, lower-gradient longitudinal profiles, and we created a “smoothness” metric as a proxy for the relative maturity of these profiles toward the idealized equilibrium profile. Generally, higher smoothness values occur in systems with larger sediment supply, and the smoothness of channels typically exceeds that of the associated continental margin. We propose that the high rates of erosion, bypass, and deposition via sediment gravity flows act to smooth and mature channel profiles more rapidly than the surrounding continental margin, which is dominated by less-energetic diffusive sedimentary processes. Additionally, tectonic deformation will act to reduce the smoothness of these longitudinal profiles. Importantly, the relationship between total sediment supply and the difference between smoothness values of associated continental margins and submarine channels (the “smoothness Δ”) follows separate trends in passive and active tectonic settings, which we attribute to the variability in relative rates of smoothness development between channelized and inter-channel environments in the presence or absence of tectonic deformation. We propose two endmember pathways by which continental margins and submarine channels coevolve towards their respective equilibrium profiles with increased sediment supply: 1) Coupled Evolution Model (common in passive tectonic settings), in which the smoothness Δ increases only slightly before remaining static, and 2) Decoupled Evolution Model (common in active tectonic settings), in which the smoothness Δ increases more rapidly and to a greater final value. Our analysis indicates that the interaction of the allogenic factors of sediment supply and tectonic deformation with the autogenic sedimentary processes characteristic of channelized and inter-channel areas of the continental margin may account for much of the variability between coevolution pathways and depositional architectures.

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Zhou, Xin, Zhong-Hai Li, Taras V. Gerya, and Robert J. Stern. "Lateral propagation–induced subduction initiation at passive continental margins controlled by preexisting lithospheric weakness." Science Advances 6, no. 10 (2020): eaaz1048. http://dx.doi.org/10.1126/sciadv.aaz1048.

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Understanding the conditions for forming new subduction zones at passive continental margins is important for understanding plate tectonics and the Wilson cycle. Previous models of subduction initiation (SI) at passive margins generally ignore effects due to the lateral transition from oceanic to continental lithosphere. Here, we use three-dimensional numerical models to study the possibility of propagating convergent plate margins from preexisting intraoceanic subduction zones along passive margins [subduction propagation (SP)]. Three possible regimes are achieved: (i) subducting slab tearing along a STEP fault, (ii) lateral propagation–induced SI at passive margin, and (iii) aborted SI with slab break-off. Passive margin SP requires a significant preexisting lithospheric weakness and a strong slab pull from neighboring subduction zones. The Atlantic passive margin to the north of Lesser Antilles could experience SP if it has a notable lithospheric weakness. In contrast, the Scotia subduction zone in the Southern Atlantic will most likely not propagate laterally.

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Schmid, Daniel W., Karthik Iyer, and Ebbe H. Hartz. "Thermal Effects at Continent-Ocean Transform Margins: A 3D Perspective." Geosciences 11, no. 5 (2021): 193. http://dx.doi.org/10.3390/geosciences11050193.

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Continental breakup along transform margins produces a sequence of (1) continent-continent, (2) continent-oceanic, (3) continent-ridge, and (4) continent-oceanic juxtapositions. Spreading ridges are the main sources of heat, which is then distributed by diffusion and advection. Previous work focused on the thermal evolution of transform margins built on 2D numerical models. Here we use a 3D FEM model to obtain the first order evolution of temperature, uplift/subsidence, and thermal maturity of potential source rocks. Snapshots for all four transform phases are provided by 2D sections across the margin. Our 3D approach yields thermal values that lie in between the previously established 2D end-member models. Additionally, the 3D model shows heat transfer into the continental lithosphere across the transform margin during the continental-continental transform stage ignored in previous studies. The largest values for all investigated quantities in the continental area are found along the transform segment between the two ridges, with the maximum values occurring near the transform-ridge corner of the trailing continental edge. This boundary segment records the maximum thermal effect up to 100 km distance from the transform. We also compare the impact of spreading rates on the thermal distribution within the lithosphere. The extent of the perturbation into the continental areas is reduced in the faster models due to the reduced exposure times. The overall pattern is similar and the maximum values next to the transform margin is essentially unchanged. Varying material properties in the upper crust of the continental areas has only a minor influence.

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Li, Sanzhong, M. Santosh, and Bor-ming Jahn. "Evolution of the Asian continent and its continental margins." Journal of Asian Earth Sciences 47 (March 2012): 1–4. http://dx.doi.org/10.1016/j.jseaes.2012.02.001.

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Tinivella, Umberta, Michela Giustiniani, Xuewei Liu, and Ingo Pecher. "Gas Hydrate on Continental Margins." Journal of Geological Research 2012 (February 27, 2012): 1–2. http://dx.doi.org/10.1155/2012/781429.

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10

White, Robert S., George D. Spence, Susan R. Fowler, Dan P. McKenzie, Graham K. Westbrook, and Adrian N. Bowen. "Magmatism at rifted continental margins." Nature 330, no. 6147 (1987): 439–44. http://dx.doi.org/10.1038/330439a0.

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11

Coleman, J. M., and D. B. Prior. "Mass Wasting on Continental Margins." Annual Review of Earth and Planetary Sciences 16, no. 1 (1988): 101–19. http://dx.doi.org/10.1146/annurev.ea.16.050188.000533.

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12

Allen, Janice, and Christopher Beaumont. "Continental margin syn-rift salt tectonics at intermediate width margins." Basin Research 28, no. 5 (2015): 598–633. http://dx.doi.org/10.1111/bre.12123.

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13

SINTON, C. W., K. HITCHEN, and R. A. DUNCAN. "40Ar–39Ar geochronology of silicic and basic volcanic rocks on the margins of the North Atlantic." Geological Magazine 135, no. 2 (1998): 161–70. http://dx.doi.org/10.1017/s0016756898008401.

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At the submerged margins of the North Atlantic, andesitic to dacitic and basaltic volcanic rocks occur together. The silicic rocks were derived by processes requiring the presence of continental crust (crustal anatexis and/or contamination of mafic magmas) while the majority of the basaltic lavas had little or no contact with continental crust. We report 40Ar–39Ar incremental heating ages for several dacitic and basaltic rocks recovered from three offshore localities of the North Atlantic Igneous Province. Dacitic lavas and tuffs at the southeast Greenland margin and trachytic lavas in the Scottish Hebrides erupted contemporaneously with basaltic lavas at 62–61 Ma. In contrast, the silicic lavas from the northern Rockall Trough (offshore western Scotland) and the Vøring Plateau (offshore Norway) erupted at ∼55 Ma followed shortly by basaltic volcanism. At this time, silicic magmatism at the southeast Greenland margin had ceased and only oceanic basalts were erupted. Similarly, ∼55 Ma lavas on the southwest Rockall Plateau are wholly basaltic. The compositions of all of the dated silicic volcanic rocks are consistent with derivation from partial melting of either continental crust or sediments. The heat necessary for partial melting appears to have been provided by basaltic magmas. Therefore, the existence of the silicic rocks indicates the presence of continental crust as well as a stable tectonic environment that allowed the stagnation and pooling of basaltic melts within the crust. With this in mind, it is apparent that at 62–60 Ma, both western and eastern sides of the present North Atlantic margins were characterized by extensional environments within continental crust that were restrictive to the passage of mafic magmas. By 55 Ma, at the time of continental breakup, the proximal margins at southeast Greenland and the Rockall Plateau were devoid of continental crust. But the presence of 55 Ma silicic magmatism on the eastern North Atlantic margin can be attributed to a broader zone of magmatism and sediment-filled Mesozoic rift basins.

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Bonan, B., M. J. Baines, N. K. Nichols, and D. Partridge. "A moving point approach to model shallow ice sheets: a study case with radially-symmetrical ice sheets." Cryosphere Discussions 9, no. 4 (2015): 4237–70. http://dx.doi.org/10.5194/tcd-9-4237-2015.

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Abstract. Predicting the evolution of ice sheets requires numerical models able to accurately track the migration of ice sheet continental margins or grounding lines. We introduce a physically-based moving point approach for the flow of ice sheets based on the conservation of local masses. This allows the ice sheet margins to be tracked explicitly and the waiting time behaviours to be modelled efficiently. A finite difference moving point scheme is derived and applied in a simplified context (continental radially-symmetrical shallow ice approximation). The scheme, which is inexpensive, is validated by comparing the results with moving-margin exact solutions and steady states. In both cases the scheme is able to track the position of the ice sheet margin with high precision.

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15

Khabanets, I., and I. Karpenko. "TECTONIC MODEL OF JUNCTION ZONE BETWEEN DNIEPER AND DONETS SEDIMENTARY BASINS AS PROSPECTIVE TERRITORY FOR UNCONVENTIONAL HYDROCARBON." Ukrainian Geologist, no. 3(43) (October 10, 2013): 112–15. http://dx.doi.org/10.53087/ug.2013.3(43).245571.

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We give and analyze geological data that substantiate the validity division of Dnieper-Donets basin into two separate basins: Donets marginal-continental part that was opening from 793.00–590.75 Ma and Dnieper innerplatform with the disclosure in late Paleozoic – early Mesozoic (385.75–178.00 Ma). Territorially boundary between those margins passes between regional seismic profiles Lozovaja-Shebelinka-Staropokrivka and Mechebylovo-Bryhadyrivka. Donets Basin (Central Donbass) is a remnant continental margin of paleoocean Prototetis II, and north side of Donets basin up to the border of the Dnieper deflection – the remnant of the continental margin Prototetis I. 

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16

Peace, Alexander L., and J. Kim Welford. "Conjugate margins — An oversimplification of the complex southern North Atlantic rift and spreading system?" Interpretation 8, no. 2 (2020): SH33—SH49. http://dx.doi.org/10.1190/int-2019-0087.1.

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The prevalence of conjugate margin terminology and studies in the scientific literature is testimony to the contribution that this concept and approach has made to the study of passive margins, and more broadly extensional tectonics. However, when applied to the complex rift, transform, and spreading system of the southern North Atlantic (i.e., the passive margins of Newfoundland, Labrador, Ireland, Iberia, and southern Greenland), it becomes obvious that at these passive continental margin settings, additional geologic phenomena complicate this convenient description. These aspects include (1) the preservation of relatively undeformed continental fragments, (2) formation of transform systems and oblique rifts, (3) triple junctions (with rift and spreading axes), (4) multiple failed rift axes, (5) postbreakup processes such as magmatism, (6) localized subduction, and (7) ambiguity in identification of oceanic isochrons. Comparison of two different published reconstructions of the region indicates the ambiguity in conducting conjugate margin studies. This demonstrates the need for a more pragmatic approach to the study of continental passive margin settings where a greater emphasis is placed on the inclusion of these possibly complicating features in palinspastic reconstructions, plate tectonics, and evolutionary models.

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van der Ploeg, Robin, Bernard P. Boudreau, Jack J. Middelburg, and Appy Sluijs. "Cenozoic carbonate burial along continental margins." Geology 47, no. 11 (2019): 1025–28. http://dx.doi.org/10.1130/g46418.1.

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Abstract Marine carbonate burial represents the largest long-term carbon sink at Earth’s surface, occurring in both deep-sea (pelagic) environments and shallower waters along continental margins. The distribution of carbonate accumulation has varied over geological history and impacts the carbon cycle and ocean chemistry, but it remains difficult to quantitatively constrain. Here, we reconstruct Cenozoic carbonate burial along continental margins using a mass balance for global carbonate alkalinity, which integrates independent estimates for continental weathering and pelagic carbonate burial. Our results indicate that major changes in marginal carbonate burial were associated with important climate and sea-level change events, including the Eocene-Oligocene transition (ca. 34 Ma), the Oligocene-Miocene boundary Mi-1 glaciation (ca. 23 Ma), and the middle Miocene climate transition (ca. 14 Ma). In addition, we find that a major increase in continental weathering from ca. 10 Ma to the present may have driven a concomitant increase in pelagic carbonate burial. Together, our results show that changes in global climate, sea level, and continental weathering have all impacted carbonate burial over the Cenozoic, but the relative importance of these processes may have varied through time.

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18

Derry, Louis A., and Richard W. Murray. "Continental Margins and the Sulfur Cycle." Science 303, no. 5666 (2004): 1981–82. http://dx.doi.org/10.1126/science.303.5666.1981.

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19

Taylor, B., M. Coffin, W. Dietrich, et al. "Program focuses attention on continental margins." Eos, Transactions American Geophysical Union 79, no. 11 (1998): 137. http://dx.doi.org/10.1029/98eo00097.

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20

Brocher, Thomas M. "Deep-crustal seismology of continental margins." Reviews of Geophysics 33 (1995): 309. http://dx.doi.org/10.1029/95rg00109.

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21

D. Cocker, Earl A. Shapiro, Mark. "The Continental Margins Program in Georgia." Marine Georesources & Geotechnology 17, no. 2-3 (1999): 199–209. http://dx.doi.org/10.1080/106411999273873.

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22

Masson, D. "Geology and geophysics of continental margins." Marine and Petroleum Geology 10, no. 4 (1993): 404–5. http://dx.doi.org/10.1016/0264-8172(93)90087-9.

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23

Westaway, Rob. "Geology and geophysics of continental margins." Journal of Structural Geology 15, no. 1 (1993): 119–20. http://dx.doi.org/10.1016/0191-8141(93)90085-o.

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24

Bonan, B., M. J. Baines, N. K. Nichols, and D. Partridge. "A moving-point approach to model shallow ice sheets: a study case with radially symmetrical ice sheets." Cryosphere 10, no. 1 (2016): 1–14. http://dx.doi.org/10.5194/tc-10-1-2016.

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Abstract. Predicting the evolution of ice sheets requires numerical models able to accurately track the migration of ice sheet continental margins or grounding lines. We introduce a physically based moving-point approach for the flow of ice sheets based on the conservation of local masses. This allows the ice sheet margins to be tracked explicitly. Our approach is also well suited to capture waiting-time behaviour efficiently. A finite-difference moving-point scheme is derived and applied in a simplified context (continental radially symmetrical shallow ice approximation). The scheme, which is inexpensive, is verified by comparing the results with steady states obtained from an analytic solution and with exact moving-margin transient solutions. In both cases the scheme is able to track the position of the ice sheet margin with high accuracy.

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25

McDermott, Kenneth, Paul Bellingham, Rod Graham, et al. "Continental extension and break-up—using the Australian margins as a case study." APPEA Journal 55, no. 2 (2015): 399. http://dx.doi.org/10.1071/aj14034.

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The continental margins of Australia provide an excellent natural laboratory for investigations of continental extension and break-up, with examples of failed rifts, multi-phase extensional systems, and volcanic and non-volcanic margins. The thick sedimentary cover across large parts, however, has hindered understanding of the deep crustal and lithospheric structure due to poor imaging. ION Geophysical has acquired deep, long offset seismic data across Australia’s North West Shelf, as well as the Bight Basin on Australia’s southern margin. These programs provide unique imaging of the deep basement structures and the complete overlying sedimentary section, and across all of the terrains from continental crust to oceanic crust. The authors’ interpretation of these data will be discussed in the context of existing models for continental extension and break-up and the resulting implications for the petroleum system: Models of hyper-extension and possible mantle exhumation will be discussed with regards to the Bonaparte, Browse and Bight basins. Multi-phase extension and the development of intra-sedimentary detachment horizons will be reviewed across many areas. Development of volcanic margins, including the effects of dynamic uplift and magmatic intrusions, will be investigated in the Exmouth Plateau. Creation of enough accommodation space to allow the deposition of the observed (~20 km) sedimentary sections in the Carnarvon and Bonaparte basins.

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26

Berndt, Christian. "Focused fluid flow in passive continental margins." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 363, no. 1837 (2005): 2855–71. http://dx.doi.org/10.1098/rsta.2005.1666.

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Passive continental margins such as the Atlantic seaboard of Europe are important for society as they contain large energy resources, and they sustain ecosystems that are the basis for the commercial fish stock. The margin sediments are very dynamic environments. Fluids are expelled from compacting sediments, bottom water temperature changes cause gas hydrate systems to change their locations and occasionally large magmatic intrusions boil the pore water within the sedimentary basins, which is then expelled to the surface. The fluids that seep through the seabed at the tops of focused fluid flow systems have a crucial role for seabed ecology, and study of such fluid flow systems can also help in predicting the distribution of hydrocarbons in the subsurface and deciphering the climate record. Therefore, the study of focused fluid flow will become one of the most important fields in marine geology in the future.

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Nelson, C. H., J. Gutiérrez Pastor, C. Goldfinger, and C. Escutia. "Great earthquakes along the Western United States continental margin: implications for hazards, stratigraphy and turbidite lithology." Natural Hazards and Earth System Sciences 12, no. 11 (2012): 3191–208. http://dx.doi.org/10.5194/nhess-12-3191-2012.

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Abstract. We summarize the importance of great earthquakes (Mw &amp;gtrsim; 8) for hazards, stratigraphy of basin floors, and turbidite lithology along the active tectonic continental margins of the Cascadia subduction zone and the northern San Andreas Transform Fault by utilizing studies of swath bathymetry visual core descriptions, grain size analysis, X-ray radiographs and physical properties. Recurrence times of Holocene turbidites as proxies for earthquakes on the Cascadia and northern California margins are analyzed using two methods: (1) radiometric dating (14C method), and (2) relative dating, using hemipelagic sediment thickness and sedimentation rates (H method). The H method provides (1) the best estimate of minimum recurrence times, which are the most important for seismic hazards risk analysis, and (2) the most complete dataset of recurrence times, which shows a normal distribution pattern for paleoseismic turbidite frequencies. We observe that, on these tectonically active continental margins, during the sea-level highstand of Holocene time, triggering of turbidity currents is controlled dominantly by earthquakes, and paleoseismic turbidites have an average recurrence time of ~550 yr in northern Cascadia Basin and ~200 yr along northern California margin. The minimum recurrence times for great earthquakes are approximately 300 yr for the Cascadia subduction zone and 130 yr for the northern San Andreas Fault, which indicates both fault systems are in (Cascadia) or very close (San Andreas) to the early window for another great earthquake. On active tectonic margins with great earthquakes, the volumes of mass transport deposits (MTDs) are limited on basin floors along the margins. The maximum run-out distances of MTD sheets across abyssal-basin floors along active margins are an order of magnitude less (~100 km) than on passive margins (~1000 km). The great earthquakes along the Cascadia and northern California margins cause seismic strengthening of the sediment, which results in a margin stratigraphy of minor MTDs compared to the turbidite-system deposits. In contrast, the MTDs and turbidites are equally intermixed on basin floors along passive margins with a mud-rich continental slope, such as the northern Gulf of Mexico. Great earthquakes also result in characteristic seismo-turbidite lithology. Along the Cascadia margin, the number and character of multiple coarse pulses for correlative individual turbidites generally remain constant both upstream and downstream in different channel systems for 600 km along the margin. This suggests that the earthquake shaking or aftershock signature is normally preserved, for the stronger (Mw ≥ 9) Cascadia earthquakes. In contrast, the generally weaker (Mw = or <8) California earthquakes result in upstream simple fining-up turbidites in single tributary canyons and channels; however, downstream mainly stacked turbidites result from synchronously triggered multiple turbidity currents that deposit in channels below confluences of the tributaries. Consequently, both downstream channel confluences and the strongest (Mw ≥ 9) great earthquakes contribute to multi-pulsed and stacked turbidites that are typical for seismo-turbidites generated by a single great earthquake. Earthquake triggering and multi-pulsed or stacked turbidites also become an alternative explanation for amalgamated turbidite beds in active tectonic margins, in addition to other classic explanations. The sedimentologic characteristics of turbidites triggered by great earthquakes along the Cascadia and northern California margins provide criteria to help distinguish seismo-turbidites in other active tectonic margins.

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Reuber, Kyle, Paul Mann, and Jim Pindell. "Hotspot origin for asymmetrical conjugate volcanic margins of the austral South Atlantic Ocean as imaged on deeply penetrating seismic reflection lines." Interpretation 7, no. 4 (2019): SH71—SH97. http://dx.doi.org/10.1190/int-2018-0256.1.

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We have interpreted 27,550 km of deep-penetrating, 2D-seismic reflection profiles across the South Atlantic conjugate margins of Uruguay/Southern Brazil and Namibia. These reflection profiles reveal in unprecedented detail the lateral and cross-sectional, asymmetrical distribution of voluminous, postrift volcanic material erupted during the Barremian-Aptian (129–125 Ma) period of early seafloor spreading in the southernmost South Atlantic. Using this seismic grid, we mapped the 10–200 km wide, continental margin-parallel limits of seaward-dipping reflector (SDR) complexes — that are coincident with interpretations from previous workers using seismic refraction data from the South American and West African conjugate margins. Subaerially emplaced and tabular SDRs have rotated downward 20° in the direction of the mid-Atlantic spreading ridge and are up to 22 km thick near the limit of continental crust. The SDR package is wedge shaped and thins abruptly basinward toward the limit of oceanic crust where it transitions to normal, 6–8 km thick oceanic crust. We have developed a model for the conjugate rifted margins that combine diverging tectonic plates and northwesterly plate motion relative to a fixed mantle position of the mantle plume. Our model explains an approximately 30% higher volume of SDRs/igneous crust on the trailing Namibian margin than on the leading Brazilian margin during the syn- and postrift phases. Our model for volcanic margin asymmetry in the South Atlantic does not require a simple shear mechanism to produce the asymmetrical volcanic material distribution observed from our data and from previously published seismic refraction studies. Determining the basinward extent of the extended continental basement is crucial for understanding basin evolution and for hydrocarbon exploration. Although these conjugate margins have evolved asymmetrically, their proximity during the early postrift stage suggests a near-equivalent, early basin evolution and similar hydrocarbon potential. Understanding the tectonic and magnetic processes that produce these observed asymmetries is critical for understanding volcanic passive margin evolution.

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Tuitt, Adrian, Simon Holford, Richard Hillis, et al. "Continental margin compression: a comparison between compression in the Otway Basin of the southern Australian margin and the Rockall-Faroe area in the northeast Atlantic margin." APPEA Journal 51, no. 1 (2011): 241. http://dx.doi.org/10.1071/aj10017.

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There is growing recognition that many passive margins have undergone compressional deformation subsequent to continental breakup, including the southern Australian margin. This deformation commonly results in formation of domal anticlines with four-way dip closures that are attractive targets for hydrocarbon exploration, and many such structures host major hydrocarbon accumulations in the Otway and Gippsland basins; however, the driving mechanisms behind formation of these structures are not completely understood. We compare the history of post-breakup compression in the Otway Basin of the southern Australian margin, with that of the Rockall-Faroe area of the northeast Atlantic margin, which has been far more extensively studied with the aim of establishing a better understanding of the genesis and prospectivity of such structures. Both margins have experienced protracted Mesozoic rifting histories culminating in final continental separation in the Eocene, followed by distinct phases of compressional deformation and trap formation. Whilst the structural style of the anticlines in both margins is similar (mainly fault-propagation folds formed during tectonic inversion), the number, amplitude, and length of the structures in the northeast Atlantic margin are much higher than the southern Australian margin. We propose that compressional structures at both margins formed due to far-field stresses related to plate boundaries, but the magnitude of these stresses in the northeast Atlantic margin is likely to have been higher, and the strength of the lithosphere lower. In the northeast Atlantic margin, the presence of Early Cenozoic basalt lava flows may have also contributed to an increase in pore-fluid pressure in the underlying sediment making pre-existing faults more prone to reactivation.

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Chew, David M., and Cees R. Van Staal. "The Ocean – Continent Transition Zones Along the Appalachian – Caledonian Margin of Laurentia: Examples of Large-Scale Hyperextension During the Opening of the Iapetus Ocean." Geoscience Canada 41, no. 2 (2014): 165. http://dx.doi.org/10.12789/geocanj.2014.41.040.

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A combination of deep seismic imaging and drilling has demonstrated that the ocean-continent transition (OCT) of present-day, magma-poor, rifted continental margins is a zone of hyperextension characterized by extreme thinning of the continental crust that exhumed the lowermost crust and/or serpentinized continental mantle onto the seafloor. The OCT on present-day margins is difficult to sample, and so much of our knowledge on the detailed nature of OCT sequences comes from obducted, magma-poor OCT ophiolites such as those preserved in the upper portions of the Alpine fold-and-thrust belt. Allochthonous, lens-shaped bodies of ultramafic rock are common in many other ancient orogenic belts, such as the Caledonian – Appalachian orogen, yet their origin and tectonic significance remains uncertain. We summarize the occurrences of potential ancient OCTs within this orogen, commencing with Laurentian margin sequences where an OCT has previously been inferred (the Dalradian Supergroup of Scotland and Ireland and the Birchy Complex of Newfoundland). We then speculate on the origin of isolated occurrences of Alpine-type peridotite within Laurentian margin sequences in Quebec – Vermont and Virginia – North Carolina, focusing on rift-related units of Late Neoproterozoic age (so as to eliminate a Taconic ophiolite origin). A combination of poor exposure and pervasive Taconic deformation means that origin and emplacement of many ultramafic bodies in the Appalachians will remain uncertain. Nevertheless, the common occurrence of OCT-like rocks along the whole length of the Appalachian – Caledonian margin of Laurentia suggests that the opening of the Iapetus Ocean may have been accompanied by hyperextension and the formation of magma-poor margins along many segments.SOMMAIREDes travaux d’imagerie sismique et des forages profonds ont montré que la transition océan-continent (OCT) de marges continentales de divergence pauvre en magma exposée de nos jours, correspond à une zone d’hyper-étirement tectonique caractérisée par un amincissement extrême de la croûte continentale, qui a exhumé sur le fond marin, jusqu’à la tranche la plus profonde de la croûte continentale, voire du manteau continental serpentinisé. Parce qu’on peut difficilement échantillonner l’OCT sur les marges actuelles, une grande partie de notre compréhension des détails de la nature de l’OCT provient d’ophiolites pauvres en magma d’une OCT obduite, comme celles préservées dans les portions supérieures de la bande plissée alpine. Des masses lenticulaires de roches ultramafiques allochtones sont communes dans de nombreuses autres bandes orogéniques anciennes, comme l’orogène Calédonienne-Appalaches, mais leur origine et signification tectonique reste incertaine. Nous présentons un sommaire des occurrences d’OCT potentielles anciennes de cet orogène, en commençant par des séquences de la marge laurentienne, où la présence d’OCT a déjà été déduites (le Supergroupe Dalradien d’Écosse et d'Irlande, et le complexe de Birchy de Terre-Neuve). Nous spéculons ensuite sur l'origine de cas isolés de péridotite de type alpin dans des séquences de marge des Laurentides du Québec-Vermont et de la Virginie-Caroline du Nord, en nous concentrant sur les unités de rift d'âge néoprotérozoïque tardif (pour éviter les ophiolites du Taconique). La conjonction d’affleurements de piètre qualité et de la déformation taconique omniprésente, signifie que l'origine et la mise en place de nombreuses masses ultramafiques dans les Appalaches demeureront incertaines. Néanmoins, la présence fréquente de roches de type OCT tout le long de la marge Calédonnienne-Appalaches de Laurentia suggère que l'ouverture de l'océan Iapetus peut avoir été accompagnée d’hyper-étirement et de la formation de marges pauvres en magma le long de nombreux segments.

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Alves, Tiago M., Julie Tugend, Simon Holford, Claudia Bertoni, and Wei Li. "Editorial: Continental margins unleashed - From their early inception to continental breakup." Marine and Petroleum Geology 129 (July 2021): 105097. http://dx.doi.org/10.1016/j.marpetgeo.2021.105097.

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LEELANANDAM, C., K. BURKE, L. D. ASHWAL, and S. J. WEBB. "Proterozoic mountain building in Peninsular India: an analysis based primarily on alkaline rock distribution." Geological Magazine 143, no. 2 (2006): 195–212. http://dx.doi.org/10.1017/s0016756805001664.

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Peninsular India was assembled into a continental block c. 3 million km2 in area as a result of collisions throughout the length of a 4000 km long S-shaped mountain belt that was first recognized from the continuity of strike of highly deformed Proterozoic granulites and gneisses. More recently the recognition of a variety of tectonic indicators, including occurrences of ophiolitic slivers, Andean-margin type rocks, a collisional rift and a foreland basin, as well as many structural and isotopic age studies have helped to clarify the history of this Great Indian Proterozoic Fold Belt. We here complement those studies by considering the occurrence of deformed alkaline rocks and carbonatites (DARCs) in the Great Indian Proterozoic Fold Belt. One aim of this study is to test the recently published idea that DARCs result from the deformation of alkaline rocks and carbonatites (ARCs) originally intruded into intra-continental rifts and preserved on rifted continental margins. The suggestion is that ARCs from those margins are transformed into DARCs during continental, or arc–continental, collisions. If that idea is valid, DARCs lie on rifted continental margins and on coincident younger suture zones; they occur in places where ancient oceans have both opened and closed. Locating sutures within mountain belts has often proved difficult and has sometimes been controversial. If the new idea is valid, DARC distributions may help to reduce controversy. This paper concentrates on the Eastern Ghats Mobile Belt of Andhra Pradesh and Orissa, where alkaline rock occurrences are best known. Less complete information from Kerala, Tamil Nadu, Karnataka, West Bengal, Bihar and Rajasthan has enabled us to define a line of 47 unevenly distributed DARCs with individual outcrop lengths of between 30 m and 30 km that extends along the full 4000 km length of the Great Indian Proterozoic Fold Belt. Ocean opening along the rifted margins of the Archaean cratons of Peninsular India may have begun by c. 2.0 Ga and convergent plate margin phenomena have left records within the Great Indian Proterozoic Fold Belt and on the neighbouring cratons starting at c. 1.8 Ga. Final continental collisions were over by 0.55 Ga, perhaps having been completed at c. 0.75 Ga or at c. 1 Ga. Opening of an ocean at the Himalayan margin of India by c. 0.55 Ga removed an unknown length of the Great Indian Proterozoic Fold Belt. In the southernmost part of the Indian peninsula, a line of DARCs, interpreted here as marking a Great Indian Proterozoic Fold Belt suture, can be traced within the Southern Granulite Terrain almost to the Achankovil-Tenmala shear zone, which is interpreted as a strike-slip fault that also formed at c. 0.55 Ga.

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Dell'Anno, A., A. Pusceddu, C. Corinaldesi, et al. "Trophic state of sediments from two deep continental margins off Iberia: a biomimetic approach." Biogeosciences Discussions 9, no. 12 (2012): 17619–50. http://dx.doi.org/10.5194/bgd-9-17619-2012.

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Abstract. The trophic state of benthic deep-sea ecosystems can greatly influence key ecological processes (e.g. biomass production and nutrient cycling). Thus, assessing the trophic state of the sediment at different spatial and temporal scales is crucial for a better understanding of deep-sea ecosystem functioning. Here, using a biomimetic approach based on enzymatic digestion of protein and carbohydrate pools, we assess the bioavailability of organic detritus and its nutritional value in the uppermost layer of deep-sea sediments from open slopes and canyons of the Catalan (NW Mediterranean) and Portuguese (NE Atlantic) continental margins, offshore east and west Iberia, respectively. Patterns of sediment trophic state were analyzed in relation to increasing water depth, including repeated samplings over a 3 yr period in the Catalan margin. Bioavailable organic matter and its nutritional value were significantly higher in the Portuguese margin than in the Catalan margin, thus reflecting differences in primary productivity of surface waters reported for the two regions. Similarly, sediments of the Catalan margin were characterized by significantly higher food quantity and quality in spring, when higher primary production processes occur in surface waters, than in summer and autumn. In both continental margins, bioavailable organic C concentrations did not vary or increase with increasing water depth. Differences in the benthic trophic state of canyons against open slopes were more evident in the Portuguese than in the Catalan margin. Overall our findings indicate that deep-sea sediments are characterized by relatively high amounts of bioavailable organic matter. We suggest that the interactions between biological-related processes in surface waters and particle transport and deposition dynamics can play a crucial role in shaping the quantity and distribution of bioavailable organic detritus and its nutritional value along deep continental margins.

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Steventon, Michael J., Christopher A.-L. Jackson, David M. Hodgson, and Howard D. Johnson. "Lateral variability of shelf-edge and basin-floor deposits, Santos Basin, offshore Brazil." Journal of Sedimentary Research 90, no. 9 (2020): 1198–221. http://dx.doi.org/10.2110/jsr.2020.14.

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ABSTRACT Construction of continental margins is driven by sediment transported across the shelf to the shelf edge, where it is reworked by wave, tide, and fluvial processes in deltas and flanking clastic shorelines. Stalling of continental-margin progradation often results in degradation of the outer shelf to upper slope, with resedimentation to the lower slope and basin floor via a range of sediment gravity flows and mass-movement processes. Typically, our understanding of how these processes contribute to the long-term development of continental margins has been limited to observations from broadly two-dimensional, subsurface and outcrop datasets. Consequently, the three-dimensional variability in process regime and margin evolution is poorly constrained and often underappreciated. We use a large (90 km by 30 km, parallel to depositional strike and dip, respectively) post-stack time-migrated 3D seismic-reflection dataset to investigate along-strike variations in shelf-margin progradation and outer-shelf to upper-slope collapse in the Santos Basin, offshore SE Brazil. Early Paleogene to Eocene progradation of the shelf margin is recorded by spectacularly imaged, SE-dipping clinoforms. Periodic failure of the outer shelf and upper slope formed ca. 30-km-wide (parallel to shelf-margin strike) slump scars, which resulted in a strongly scalloped upper-slope. Margin collapse caused: 1) the emplacement of slope-attached mass-transport complexes (MTCs) (up to ca. 375 m thick, 12+ km long, 20 km wide) on the proximal basin floor, and 2) accommodation creation on the outer shelf to upper slope. This newly formed accommodation was infilled by shelf-edge-delta clinoforms (up to 685 m thick), that nucleated and prograded basinward from the margin-collapse headwall scarp, downlapping onto the underlying slump scar and/or MTCs. Trajectory analysis of the shelf-edge deltas suggests that slope degradation-created accommodation was generated throughout the sea-level cycle, rather than during base-level fall as would be predicted by conventional sequence-stratigraphic models. Our results highlight the significant along-strike variability in depositional style, geometry, and evolution that can occur on this and other continental margins. Coeval strata, separated by only a few kilometers, display strikingly different stratigraphic architectures; this variability, which could be missed in 2D datasets, is not currently captured in conventional 2D sequence stratigraphic models.

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Brune, Sascha, Simon E. Williams, Nathaniel P. Butterworth, and R. Dietmar Müller. "Abrupt plate accelerations shape rifted continental margins." Nature 536, no. 7615 (2016): 201–4. http://dx.doi.org/10.1038/nature18319.

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YUAN, Sihua, Guitang PAN, Liquan WANG, et al. "Accretionary Orogenesis in the Active Continental Margins." Earth Science Frontiers 16, no. 3 (2009): 31–48. http://dx.doi.org/10.1016/s1872-5791(08)60095-0.

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Soltwedel, T. "Metazoan meiobenthos along continental margins: a review." Progress in Oceanography 46, no. 1 (2000): 59–84. http://dx.doi.org/10.1016/s0079-6611(00)00030-6.

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Dilek, Yildirim, and Ron Harris. "Continental margins of the Pacific Rim: introduction." Tectonophysics 392, no. 1-4 (2004): 1–7. http://dx.doi.org/10.1016/j.tecto.2004.06.005.

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Morford, Jennifer L., William R. Martin, and Caitlin M. Carney. "Rhenium geochemical cycling: Insights from continental margins." Chemical Geology 324-325 (September 2012): 73–86. http://dx.doi.org/10.1016/j.chemgeo.2011.12.014.

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40

Mienert, J., J. Thiede, N. H. Kenyon, and F. J. Hollender. "Polar continental margins: Studies off East Greenland." Eos, Transactions American Geophysical Union 74, no. 20 (1993): 225–36. http://dx.doi.org/10.1029/93eo00294.

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HINZ, K., O. ELDHOLM, M. BLOCK, and J. SKOGSEID. "Evolution of North Atlantic volcanic continental margins." Geological Society, London, Petroleum Geology Conference series 4, no. 1 (1993): 901–13. http://dx.doi.org/10.1144/0040901.

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Zabanbark, A., A. I. Konyuhov, and L. I. Lobkovsky. "Formation of Gas Accumulation on the East African Continental Margins." Океанология 63, no. 3 (2023): 475–81. http://dx.doi.org/10.31857/s0030157423030152.

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At present the continental margin of the South-East Africa is in the process of actives search prospecting. However on like of the West African continental margins, where throughout its entire length discovered mainly liquid hydrocarbons, in researching region known on the whole only gas accumulations. The reason for this is most likely the Karoo complex formation dating at early Permian, which is widespread at the East African basins. Enormous reserves of coal contained in the section of the Karoo formation in different basins (basin Karoo in SAR). Complex Karoo extending from south-west to north-east and little by little reduced not only by thickness, but in the content of coal reserve in it. The regions where the complex reduced at the north – east of the South- East Africa, appeared oil accumulation, like as in Lamu basin (Kenia), Somali and etc. Large gas reserves are discovered at the continental margin of the South-East Africa in Rovuma basin, North Mozambique and South Tanzania. This basin is nearest neighbor just the Karoo basin. Today Mozambique becomes a gas State in the Indian Ocean.

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Mutter, John C. "Seaward dipping reflectors and the continent-ocean boundary at passive continental margins." Tectonophysics 114, no. 1-4 (1985): 117–31. http://dx.doi.org/10.1016/0040-1951(85)90009-5.

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Urlaub, Morelia, Isabel Kratzke, and Berit Oline Hjelstuen. "A numerical investigation of excess pore pressures and continental slope stability in response to ice-sheet dynamics." Geological Society, London, Special Publications 500, no. 1 (2019): 255–66. http://dx.doi.org/10.1144/sp500-2019-185.

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AbstractSubmarine landslides are common at glaciated continental margins. The onset of large-scale landslides coincides with the initiation of Northern Hemisphere glaciations in the Quaternary. This implies that processes related to glacial cycling provide favourable conditions for submarine landslides at high-latitude margins. Potential processes include glacial deposition patterns and enhanced seismicity. It is also possible that advances and retreats of ice sheets, a highly dynamic process in geological terms, makes slopes discernible to failure by modifying the stress regime. Here, we quantify this effect using 2D finite element modelling of a glaciated continental margin. Different model runs investigate the pore-pressure development in homogeneous, as well as layered, slopes during glaciation when loaded by an ice stream with one or more ice advances. Ice streams cause significant variations in excess pore pressure in the very shallow sediment sequences at the continental shelf. However, lateral fluid flow is not efficient enough to increase pore pressures significantly at the slope, where large-scale submarine slides are observed. Hence, while ice-sheet dynamics appear to favour the occurrence of shallow slides close to the shelf edge, ice sheets seem to be irrelevant for the generation of large-scale submarine landslides at the continental slope.

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Todd, B. J., and C. E. Keen. "Temperature effects and their geological consequences at transform margins." Canadian Journal of Earth Sciences 26, no. 12 (1989): 2591–603. http://dx.doi.org/10.1139/e89-221.

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A thermal model of transform-margin evolution, including both shear heating and lateral conduction of heat from hot oceanic to colder lithosphere, was developed to gain insight into transform-margin crustal structure. Results indicate that over 2 km of crustal uplift may occur at the fault trace for a modelled transform fault 500 km in length with spreading half-rates of 1.0 and 4.0 cm/year. This uplift decreases away from the fault over a distance of 60–80 km. The viscosity of the lower continental crust and upper mantle adjacent to the transform margin is reduced by a factor of more than 100. In response to plate motion and asthenospheric upwelling at the spreading ridge, flow of this thermally weakened material may also play a role in continental crustal thinning.Thermal model predictions are compared with geological observations and crustal structure across transform margins. In particular, we show that the geology of the Southwest Newfoundland Transform Margin, eastern Canada, and the Cape Range fracture zone, Western Australia, supports the model predictions of uplift, erosion, and crustal thinning.

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Lyakhovsky, V., A. Segev, U. Schattner, and R. Weinberger. "Deformation and seismicity associated with continental rift zones propagating toward continental margins." Geochemistry, Geophysics, Geosystems 13, no. 1 (2012): n/a. http://dx.doi.org/10.1029/2011gc003927.

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Dortch, Charles. "Prehistory Down Under: archaeological investigations of submerged Aboriginal sites at Lake Jasper, Western Australia." Antiquity 71, no. 271 (1997): 116–23. http://dx.doi.org/10.1017/s0003598x0008460x.

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Much of Australian prehistory lies under water. Although confined to the continent's extreme southwestern corner, field studies described in this report show that this submerged prehistoric component is very real, with numerous archaeological sites and former land surfaces awaiting investigation on the floors of Australia's lakes, rivers and estuaries, and on its submerged continental margins.

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48

Keen, C. E., P. Potter, and S. P. Srivastava. "Deep seismic reflection data across the conjugate margins of the Labrador Sea." Canadian Journal of Earth Sciences 31, no. 1 (1994): 192–205. http://dx.doi.org/10.1139/e94-016.

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A deep seismic reflection transect of the conjugate margins of the Labrador Sea is described, which represents one of the few data sets of this kind. A characteristic reflectivity is ascribed to a 120 km wide ribbon of very thin crust that may be either thinned continental crust, which has perhaps been intruded, or oceanic crust, perhaps modified by the proximity of the continent. Most of the major changes in crustal thickness and in the subsidence and sedimentation patterns on the margins occur landward of these transitional zones, which are found on both margins. An interpretation of these regions as continental in origin is compatible with other seismic observations on the west Greenland margin, but does not match the magnetic anomaly interpretation, which requires the transitional crust to be oceanic in origin. Models that satisfy the gravity anomalies and the subsidence history have been used to assist in interpreting the seismic data. The subsidence models include the effects of decompression melting during lithospheric extension and rifting, and we predict the thickness of igneous crust produced. However, the gravity models suggest that a lower crustal layer may extend farther inland below the Labrador shelf than is predicted by magmatic underplating. The present seismic results, combined with the other geophysical data, are consistent with a pure shear model of lithospheric stretching, with faulting confined to the upper crust. Many of the problems raised by this data set are similar to those identified in comparing the nonvolcanic margin of Iberia with the conjugate Grand Banks margin in the North Atlantic. If the transition zone results from stretching the continental lithosphere, then a large component of the very thin crust there must consist of igneous material formed by melting. Under these conditions a sharp, vertical ocean–continent boundary would be unlikely.

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GELOS, EDGARDO MARTÍN, JORGE OSVALDO SPAGNUOLO, and FEDERICO IGNACIO ISLA. "Características Tectónicas de Áreas de Aporte para Arenas de Playas de Tierra del Fuego y Península Antártica, Argentina." Pesquisas em Geociências 27, no. 1 (2000): 69. http://dx.doi.org/10.22456/1807-9806.20181.

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Sand mineralogical analysis from 22 beaches were performed within the southernmost area of Argentina (Isla Grande de Tierra del Fuego), the Antarctic Peninsula and the Scotia Arc (South Orkney, South Shetland and James Ross islands included). Composition triangles of light and heavy minerals were considered in order to relate them to depocenters, sediment sources and tectonic setting. 71% of the sediments would have been transported from magmatic arcs, 24% from elevated crystalline basements and only 5% from recycled orogene. In regard to the heavy mineral distribution, 70% were assigned to a suite from an active continental margin and the remaining 30% would correspond to areas outside the continental margins (volcanic arcs). In a general way, sediment sources were related to active margins or volcanic island arcs. As an anomalous fact, it is stressed that the coasts of Tierra del Fuego and the western sector of the Antarctic Peninsula and adjacent islands, contain sediments from a Pacific margin but lying on a passive Atlantic margin. Finally, it should be adviced about the convenience to know the source areas when ice is the transport agent, as it avoids a selective ability and it does not modify the original mineralogical composition.

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ORTEGA-FLORES, BERLAINE, LUIGI A. SOLARI, and FELIPE DE JESÚS ESCALONA-ALCÁZAR. "The Mesozoic successions of western Sierra de Zacatecas, Central Mexico: provenance and tectonic implications." Geological Magazine 153, no. 4 (2015): 696–717. http://dx.doi.org/10.1017/s0016756815000977.

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AbstractCentral Mexico was subject to active tectonics related to subduction processes while it occupied a position in western equatorial Pangea during early Mesozoic time. The subduction of the palaeo-Pacific plate along the western North American and South American active continental margins produced volcanic arc successions which were subsequently rifted and re-incorporated to the continental margin. In this context, the fringing arcs are important in unravelling the continental accretionary record. Using petrographic analysis, detrital zircon geochronology and structural geology, this paper demonstrates that the Guerrero Arc (Guerrero Terrane) formed on top of a felsic volcaniclastic unit (Middle Jurassic La Pimienta Formation) and siliciclastic strata (Upper Triassic Zacatecas Formation and Arteaga Complex) of continental Mexican provenance, deposited across the continental margin and oceanic substrate. This assemblage was rifted away from continental Mexico to form an intervening oceanic assemblage (Upper Jurassic – Lower Cretaceous Las Pilas Volcanosedimentary Complex of the Arperos Basin), then accreted back more or less at the same place, all above the same east-dipping subduction zone. The accretion of the Guerrero Arc to the Mexican continental mainland (Sierra Madre Terrane) caused the deposition of a siliciclastic unit (La Escondida Phyllite), which recycled detritus from the volcaniclastic and siliciclastic underlying strata.

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Journal articles on the topic 'Continental margins'

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