scholarly journals The “Passive” Margin of Eastern North America: Rifting and the Influence of Prerift Orogenic Activity on Postrift Development

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 1-29
Author(s):  
Martha Withjack ◽  
MaryAnn Malinconico ◽  
Michael Durcanin
Keyword(s):  
Passive Margin ◽  
Rift System ◽  
Rift Basin ◽  
Rift Basins ◽  
Isostatic Rebound ◽  
Left Behind ◽  
Crustal Thinning ◽  
Hinge Zone ◽  
Uplift And Erosion ◽  
Ocean Boundary

Abstract We have analyzed and synthesized geologic and geophysical data from the onshore Newark rift basin and adjacent onshore and offshore basins to better understand the Mesozoic development of the eastern North American rift system and passive margin. Our work indicates that rifting had three phases: (1) an initial, prolonged phase of extension and subsidence; (2) a short-lived phase with higher rates of extension and subsidence, intrabasin faulting, and intense magmatism; and (3) a final phase with limited subsidence and deposition. Additionally, our work shows that anomalous uplift and erosion, associated with crustal-scale arching/warping subparallel to the prerift and syn-rift crustal fabric not the continent-ocean boundary, affected a region landward of the basement hinge zone. Uplift and erosion began during the final rifting phase and continued into early drifting with erosion locally exceeding 6 km. Subsequent subsidence was minimal. We propose that denudation unloading related to relic, prerift orogenic crustal thickness and elevated topography triggered the anomalous uplift and erosion. After the Paleozoic orogenies, postorogenic denudation unloading (cyclic erosion and isostatic rebound/uplift) significantly thinned the thickened crust and reduced topographic elevation. During rifting, extension stretched and tectonically thinned the crust, promoting widespread subsidence and deposition that dampened the postorogenic cycle of erosion and isostatic rebound/uplift. During the rift-drift transition, with extension focused near the breakup site, denudation unloading resumed landward of the basement hinge zone, producing significant erosion and uplift (related to isostatic rebound), crustal thinning, and topographic decay that left behind only eroded remnants of the once massive rift basins.

scholarly journals Inversion of gravity data with isostatic constraints

Geophysics ◽  
2014 ◽  
Vol 79 (6) ◽  
pp. A45-A50 ◽  
Author(s):  
Ahmed Salem ◽  
Chris Green ◽  
Matthew Stewart ◽  
Davide De Lerma
Keyword(s):  
Sedimentary Basin ◽  
Gravity Data ◽  
Gravity Anomalies ◽  
Gravity Inversion ◽  
Rift Basin ◽  
Rift Basins ◽  
Isostatic Equilibrium ◽  
Crustal Thinning ◽  
Model Surfaces ◽  
Gravity Profile

We have developed a simple iterative gravity-inversion approach to map the basement and Moho surfaces of a rift basin simultaneously. Gravity anomalies in rift basins commonly consist of interfering broad, positive crustal-thinning anomalies and narrow, negative sedimentary-basin anomalies. In our model, we assumed that the Moho and basement surfaces are in Airy isostatic equilibrium. An initial plane-layered model was iterated to fit the gravity data. We applied the process to a model in which the inverted basement and Moho surfaces matched the model surfaces well and to a gravity profile across the Kosti Basin in Sudan.

Effects of the tectonics of the East African Rift System on the evolution of the Tanzania margin offshore Zanzibar and Pemba Islands.

2021 ◽  
Author(s):  
Marina Dottore Stagna ◽  
Vittorio Maselli ◽  
Djordje Grujic ◽  
Pamela Reynolds ◽  
David Reynolds ◽  
...  
Keyword(s):  
Deep Water ◽  
Late Miocene ◽  
Water Channel ◽  
East African Rift ◽  
Passive Margin ◽  
Rift System ◽  
Clear Understanding ◽  
East African ◽  
Sediment Routing ◽  
African Rift

<p>The East African Rift Systems (EARS) is a modern example of a divergent plate boundary at early stages of development. In Tanzania, the rift has evolved in two branches since the Early Miocene. In addition, recent studies have proposed the existence of a marine branch of the rift in the western Indian Ocean, corresponding to the Kerimbas Graben – Davie Ridge (DR) system offshore northern Mozambique and southern Tanzania. North of this region, putative passive margin structures are present: the islands of Zanzibar and Pemba, and the troughs that separate them from the mainland. Although different theories for their formation have been proposed, a clear understanding of how the islands relate to the regional tectonic regime and the effect on the deep-water sediment routing system is lacking. </p><p>In this study, we use 2D seismic reflection profiles and exploration wells to investigate the Oligocene to recent stratigraphy offshore northern Tanzania to examine the following two questions: When did the Pemba and Zanzibar islands form? And how does the evolution of deep-water depositional systems record rift tectonics? Regional correlation of dated seismic horizons, integrated with 3D reconstruction of canyons/channels network through time, allow understanding of the main depositional events and their timing. A net decrease in the number of slope channels is visible offshore Pemba during the middle-late Miocene, which we interpreted to mark the onset of the uplift of the island. At the same time, deep-water channels were still aggrading offshore Zanzibar, indicating that the uplift of this island occurred later, likely during the late Miocene to early Pliocene. The uplift of the islands promoted the formation of a newly discovered giant canyon, characterized by a modern width of > 30 km and depth of > 485 m at > 2,200 m water depth.</p><p>The timing of the islands’ uplift indicates a potential relation with the EARS tectonics. While the structures which form the anticlines of Pemba and Zanzibar Islands may be related to Tertiary (EARS) inversion of Mesozoic-aged rift faults,  numerous high-angle normal faults, both antithetic and synthetic, dissect the post-Oligocene stratigraphy. These create horsts and grabens on a variety of scales, some of which (e.g. Kerimbas Graben and Zanzibar/Pemba trough) show comparative shape and size respect to onshore rift basins. The stratigraphic evolution of deep-water channel systems provides a tape-recorder with which to determine the modification of EARS’ tectonics on sedimentation of the older Tanzania margin.</p><p>Supported by these new results, we propose a new alternative conceptual model for the evolution of the central East African margin during the Neogene and Quaternary, highlighting the main tectonic structures and their timing of formation.</p>

Neotectonic evolution of the Brazilian northeastern continental margin based on sedimentary facies and ichnology,

2014 ◽  
Vol 82 (2) ◽  
pp. 462-472 ◽  
Author(s):  
Rosana Gandini ◽  
Dilce de Fátima Rossetti ◽  
Renata Guimarães Netto ◽  
Francisco Hilário Rego Bezerra ◽  
Ana Maria Góes
Keyword(s):  
Sea Level ◽  
Continental Margin ◽  
Sedimentary Facies ◽  
Passive Margin ◽  
South American ◽  
Soft Sediment ◽  
Rift Basins ◽  
Deformation Structures ◽  
Last Glaciation ◽  
Sediment Deformation

AbstractQuaternary post-Barreiras sediments are widespread along Brazil's passive margin. These deposits are well exposed in the onshore Paraíba Basin, which is one of the rift basins formed during the Pangean continental breakup. In this area, the post-Barreiras sediments consist of sandstones with abundant soft-sediment deformation structures related to seismicity contemporaneous with deposition. The trace fossilsThalassinoidesandPsilonichnusare found up to 38 m above modern sea level in sandstones dated between 60.0 (± 1.4) and 15.1 (± 1.8) ka. The integration of ichnological and sedimentary facies suggests nearshore paleoenvironments. Such deposits could not be related to eustatic sea-level rise, as this time coincides with the last glaciation. Hence, an uplift of 0.63 mm/yr, or 1.97 mm/yr if sea level was 80 m lower in the last glaciation, would have been required to ascend the post-Barreiras sediments several meters above the present-day sea level during the last 60 ka. This would suggest that the post-rift stage of the South American eastern passive margin may have experienced tectonic reactivation more intense than generally recognized. Although more complete data are still needed, the information presented herein may play an important role in studies aiming to decipher the Quaternary evolution of this passive margin.

The Equatorial Atlantic Laboratory: sediment routing systems and lithosphere deformation

2020 ◽  
Author(s):  
Delphine Rouby ◽  
Dominique Chardon ◽  
Jing Ye ◽  
Flora Bajolet ◽  
Artiom Loparev ◽  
...  
Keyword(s):  
West African ◽  
Passive Margin ◽  
Rift System ◽  
Equatorial Atlantic ◽  
The West ◽  
Geological Time Scale ◽  
West African Craton ◽  
Continental Scale ◽  
Sediment Routing ◽  
Atlantic Margin

<p>We summarize the results of a 7 years study of the sediment routing systems of the West African Craton transporting its erosional products to the Central and Equatorial Atlantic passive margins at geological time scale. We used paleogeograhic maps to define the geodynamics framework of this routing system with in particular the propagation of the Equatorial Atlantic oblique rift separating the West African and Amazonian Cratons. We used sub-surface data to evaluate the evolution of lithosphere necking distribution along the conjugated African and South American margins of the rift system. We estimated the long-term denudation pattern at continental scale from low temperature thermochronology measures of samples from 3 transects perpendicular to the Atlantic margin. We used the exceptional preservation of geomorphologic markers to reconstruct the drainage system of the craton since 45 Ma, and estimate the associated denudation and exports of terrigeneous sediments to the Atlantic margin. Finally, we estimated the accumulation history in the passive margin basins and compare them with the estimated denudation histories from thermal histories and geomorphologic markers. We show that the modes of preservation of sedimentary export in the passive margin basins are highly variable in time (immediate post roft versus late post-rift) and space (transform/oblique versus divergent margin segments). We show that the present day drainage of the West African Craton as been stable since 30 Ma when it underwent a major reorganization driven by the growth of the relief associated with the Hoggar mantle plume. We show that accumulation in the passive margin basins fall within the same order of magnitude than denudation on the craton at the scale of the Meso-Cenozoic. This allows us to argue to the relevance of using the stratigraphic architecture of passive margin basins to estimate the denudation history of their continental domains.</p>

Timing of subduction zone metamorphism during the formation and emplacement of Troodos and Baer–Bassit ophiolites: insights from 40Ar–39Ar geochronology

2007 ◽  
Vol 144 (5) ◽  
pp. 797-810 ◽  
Author(s):  
GAVIN HEUNG-NGAI CHAN ◽  
JOHN MALPAS ◽  
COSTAS XENOPHONTOS ◽  
CHING-HUA LO
Keyword(s):  
Subduction Zone ◽  
Late Cretaceous ◽  
Accretionary Prism ◽  
Passive Margin ◽  
Metamorphic Rocks ◽  
Metamorphic Complex ◽  
Troodos Ophiolite ◽  
Crustal Thinning ◽  
Step Heating ◽  
Short Time

The Troodos ophiolite in Cyprus and Baer–Bassit ophiolite in Syria together form part of the Tethyan ophiolite belt. They were generated in a supra-subduction zone setting in Late Cretaceous times. As with many of the ophiolite occurrences in this belt, the sequences are closely associated with tectonic ‘coloured mélange’ zones, which contain, among a variety of lithologies, metre- to kilometre-size blocks of metamorphic rocks. Precise 40Ar–39Ar laser step-heating experiments performed on four amphibolites from SW Cyprus and six from NW Syria, yield plateau ages ranging from 75.7±0.3 Ma to 88.9±0.8 Ma in Cyprus and 71.7±0.5 to 88.4±0.4 Ma in Syria. The older limits of these time spans are coeval with the age of the formation of the associated ophiolites. Unlike other metamorphic sole rocks which seem to form in relatively short time spans, these metamorphic rocks found in Cyprus and Syria are interpreted to have formed in Late Cretaceous times by accretion below the overriding Troodos and Baer–Bassit crust for a period of 15–18 Ma. The metamorphic complexes were exhumed by extension and crustal thinning associated with subduction roll-back and the rotation of the overriding plate until the cessation of subduction in Maastrichtian times. In Cyprus, the exhumed metamorphic complex was incorporated into an accretionary prism constructed primarily of the collapsed Mamonia passive margin sequence intercalated with rocks of the Troodos ophiolite during plate collision in the Maastrichtian. Concomitantly, in Syria, the Baer–Bassit ophiolite and subcreted metamorphic complex were emplaced onto the Arabian passive margin and fragmented into blocks and knockers, forming the Baer–Bassit mélange.

Synsedimentary collapse of portions of the lower Blomidon Formation (Late Triassic), Fundy rift basin, Nova Scotia

1995 ◽  
Vol 32 (11) ◽  
pp. 1965-1976 ◽  
Author(s):  
Rolf V. Ackermann ◽  
Roy W. Schlische ◽  
Paul E. Olsen
Keyword(s):  
Nova Scotia ◽  
Late Triassic ◽  
Normal Faults ◽  
Rift Basin ◽  
Rift Basins ◽  
Kink Bands ◽  
Deformation Features ◽  
Terrestrial Environments ◽  
Sediment Deformation ◽  
Fluvial Sandstone

A chaotic mudstone unit within the lower Blomidon Formation (Late Triassic) has been traced for 35 km in the Mesozoic Fundy rift basin of Nova Scotia. This unit is characterized by highly disrupted bedding that is commonly cut by small (<0.5 m) domino-style synsedimentary normal faults, downward movement of material, geopetal structures, variable thickness, and an irregular, partially faulted contact with the overlying unit. The chaotic unit is locally overlain by a fluvial sandstone, which is overlain conformably by mudstone. Although the thickness of the sandstone is highly variable, the overlying mudstone unit exhibits only gentle regional dip. The sandstone unit exhibits numerous soft-sediment deformation features, including dewatering structures, convoluted bedding, kink bands, and convergent fault fans. The frequency and intensity of these features increase dramatically above low points at the base of the sandstone unit. These stratigraphic relations suggest buried interstratal karst, the subsurface dissolution of evaporites bounded by insoluble sediments. We infer that the chaotic unit was formed by subsidence and collapse resulting from the dissolution of an evaporite bed or evaporite-rich unit by groundwater, producing dewatering and synsedimentary deformation structures in the overlying sandstone unit, which infilled surface depressions resulting from collapse. In coeval Moroccan rift basins, facies similar to the Blomidon Formation are associated with halite and gypsum beds. The regional extent of the chaotic unit indicates a marked period of desiccation of a playa lake of the appropriate water chemistry. The sedimentary features described here may be useful for inferring the former existence of evaporites or evaporite-rich units in predominantly clastic terrestrial environments.

Regional Seal as Key Controlled Elements of Petroleum Accumulation in the Rift Basin

2012 ◽  
Vol 524-527 ◽  
pp. 190-193
Author(s):  
Hai Yan Hu ◽  
Zhe Zhao ◽  
Song Lu ◽  
Hang Zhou Xiao
Keyword(s):  
Source Rock ◽  
Oil And Gas ◽  
Thickness Distribution ◽  
Normal Faults ◽  
Hydrocarbon Generation ◽  
Geological Condition ◽  
Rift Basin ◽  
Rift Basins ◽  
Northwest Germany ◽  
Petroleum Accumulation

Rift basin is an important petroleum basin type, in which about one third of oil and gas was discovered. To research on the main controlled elements of oil and gas accumulation, five typical rift basins in Europe are focused on the geological condition such as source rock, reservoir, seal, petroleum system, and accumulation with logging, hole, measured and analytical methods, and so on. The results showed the main regional seal controlled the petroleum distribution in the rift basin. Seals are defined by main regional seal, minor regional seas and local region according to thickness, distribution, lithostratigraphy. Viking Graben of North Sea has main regional seal about 3000m thick during late Jurassic and Cretaceous, about 81 percent of petroleum is in the Jurassic reservoir; Anglo-Dutch basin has main region thick seal during Triassic through Jurassic, and Permian reservoir accounted for 73 percent of basin reserves; Voring Basin has the main regional seal during Cretaceous through early Tertiary, the Jurassic reservoir has 85 percent of whole basin reserves; Northeast and Northwest Germany Basins have the evaporites as main regional seals during late Permian, and Permian reservoir accounted for more than 80 percent of basin reservoir, respectively. Rift Basin can develop reservoir like turbidite, source rock, seal in the basin dynamic opinion. Some main regional seals may develop overpressre because of quick subside and hydrocarbon generation at some conditions, it can strengthen seal capability. Oil and gas can migration to the main regional seal by normal faults caused by rifting, which can stop further migration so that they were accumulated under the main regional seal.

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