Post‐Rift Deformation of the North East and South Atlantic Margins: Are “Passive Margins” Really Passive?

Paton, Douglas

doi:10.1002/9781444347166.ch12

Cited by 6 publications

(6 citation statements)

References 49 publications

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“…The episodic nature of vertical movements at EPCMs presented here helps to clarify various issues that have long been debated. For example, in southern Africa Burke and Gunnell (2008), Tinker et al (2008a) and Paton (2012) have all highlighted an apparent conflict between evidence of Cretaceous 'uplift' defined from thermochronology and evidence for Cenozoic 'uplift' provided by more conventional methods, as discussed in chapter 6. A period of Cretaceous exhumation (leading to formation of low-relief surfaces across much of southern Africa) followed by Cenozoic uplift with only limited accompanying or subsequent erosion (taking the surfaces to their present elevations) provides a plausible explanation of the modern-day topography, and there need be no conflict between the rival interpretations (see section 6.2).…”

Section: Episodic Development Of Epcmsmentioning

confidence: 99%

Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins

Green¹,

Lidmar‐Bergström

Japsen

et al. 2013

GEUS Bulletin

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The continental margin of West Greenland is similar in many respects to other elevated, passive continental margins (EPCMs) around the world. These margins are characterised by extensive regions of low relief at elevations of 1–2 kilometres above sea level sloping gently inland, with a much steeper, oceanward decline, often termed a 'Great Escarpment', terminating at a coastal plain. Recent studies, based on integration of geological, geomorphological and thermochronological evidence, have shown that the high topography of West Greenland was formed by differential uplift and dissection of an Oligo-Miocene peneplain since the late Miocene, many millions of years after continental break-up between Greenland and North America. In contrast, many studies of other EPCMs have proposed a different style of development in which the high plateaux and the steep, oceanward decline are regarded as a direct result of rifting and continental separation. Some studies assume that the elevated regions have remained high since break-up, with the high topography continuously renewed by isostasy. Others identify the elevated plains as remnants of pre-rift landscapes. Key to understanding the development of the West Greenland margin is a new approach to the study of landforms, stratigraphic landscape analysis, in which the low-relief, high-elevation plateaux at EPCMs are interpreted as uplifted peneplains: low-relief surfaces of large extent, cutting across bedrock of different age and resistance, and originally graded to sea level. Identification of different generations of peneplain (re-exposed and epigene) from regional mapping, combined with geological constraints and thermochronology, allows definition of the evolution leading to the formation of the modern-day topography. This approach is founded particularly on results from the South Swedish Dome, which document former sea levels as base levels for the formation of peneplains. These results support the view that peneplains grade towards base level, and that in the absence of other options (e.g. widespread resistant lithologies), the most likely base level is sea level. This is particularly so at continental margins due to their proximity to the adjacent ocean. Studies in which EPCMs are interpreted as related to rifting or break-up commonly favour histories involving continuous denudation of margins following rifting, and interpretation of thermochronology data in terms of monotonic cooling histories. However, in several regions, including southern Africa, south-east Australia and eastern Brazil, geological constraints demonstrate that such scenarios are inappropriate, and an episodic development involving post-breakup subsidence and burial followed later by uplift and denudation is more realistic. Such development is also indicated by the presence in sedimentary basins adjacent to many EPCMs of major erosional unconformities within the post-breakup sedimentary section which correlate with onshore denudation episodes. The nature of the processes responsible is not yet understood, but it seems likely that plate-scale forces are required in order to explain the regional extent of the effects involved. New geodynamic models are required to explain the episodic development of EPCMs, accommodating post-breakup subsidence and burial as well as subsequent uplift and denudation, long after break-up which created the characteristic, modern-day EPCM landscapes.

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Section: Episodic Development Of Epcmsmentioning

confidence: 99%

Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins

Green¹,

Lidmar‐Bergström

Japsen

et al. 2013

GEUS Bulletin

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“…Passive continental margins, as the term explicitly implies, have been characterized by an apparent tectonic stability following their formation by intracontinental rifting and breakup [Braun and Beaumont, 1989;Lister et al, 1991;Ziegler and Cloetingh, 2004]. However, a growing body of work is questioning this view and providing better insight into the thermal and structural processes that operate during rifting and influence the long-term geomorphic development of extensional continental margins and their interior hinterlands [Péron-Pinvidic and Manatschal, 2009;Bronner et al, 2011;Paton, 2012;Dauteuil et al, 2013;Masini et al, 2013;Karl et al, 2013;Péron-Pinvidic et al, 2013;Brune et al, 2014;Huismans and Beaumont, 2014;Koopmann et al, 2014;Salomon et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U‐Th‐Sm)/He thermochronology

et al. 2016

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Atlantic-type continental margins have long been considered "passive" tectonic settings throughout the entire postrift phase. Recent studies question the long-term stability of these margins and have shown that postrift uplift and reactivation of preexisting structures may be a common feature of a continental margin's evolution. The Namaqualand sector of the western continental margin of South Africa is characterized by a ubiquitously faulted basement but lacks preservation of younger geological strata to constrain postrift tectonic fault activity. Here we present the first systematic study using joint apatite fission track and apatite (U-Th-Sm)/He thermochronology to achieve a better understanding on the chronology and tectonic style of landscape evolution across this region. Apatite fission track ages range from 58.3 ± 2.6 to 132.2 ± 3.6 Ma, with mean track lengths between 10.9 ± 0.19 and 14.35 ± 0.22 μm, and mean (U-Th-Sm)/He sample ages range from 55.8 ± 31.3 to 120.6 ± 31.4 Ma. Joint inverse modeling of these data reveals two distinct episodes of cooling at approximately 150-130 Ma and 110-90 Ma with limited cooling during the Cenozoic. Estimates of denudation based on these thermal histories predict approximately 1-3 km of denudation coinciding with two major tectonic events. The first event, during the Early Cretaceous, was driven by continental rifting and the development and removal of synrift topography. The second event, during the Late Cretaceous, includes localized reactivation of basement structures as well as regional mantle-driven uplift. Relative tectonic stability prevailed during the Cenozoic, and regional denudation over this time is constrained to be less than 1 km.

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“…The faulted, intruded, and heated continental lithosphere on either side of the spreading center loses heat and subsides as the deformation shifts to a narrow ridge fl anked by the widening, subsiding zone of oceanic lithosphere. The post-rift sedimentary strata deposited near or below sea level on the two passive margins record the detailed history of vertical crustal movements after breakup, but these thick sedimentary sequences also mask the syn-rift faults, intrusions, and sediments informing breakup processes (e.g., Steckler and Watts, 1982;Hutchinson et al, 1982;Leroy et al, 2010;Paton, 2012).…”

Section: Introductionmentioning

confidence: 99%

The time scales of continental rifting: Implications for global processes

Ebinger

Wijk

Keir

2013

The Web of Geological Sciences: Advances, Impacts, and Interactions

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The rifting cycle initiates with stress buildup, release as earthquakes and/or magma intrusions/eruptions, and visco-elastic rebound, multiple episodes of which combine to produce the observed, time-averaged rift zone architecture. The aim of our synthesis of current research initiatives into continental rifting-to-rupture processes is to quantify the time and length scales of faulting and magmatism that produce the time-averaged rift structures imaged in failed rifts and passive margins worldwide. We compare and contrast seismic and geodetic strain patterns during discrete, intense rifting episodes in magmatic and amagmatic sectors of the East African rift zone that span early-to late-stage rifting. We also examine the longer term rifting cycle and its relation to changing far-fi eld extension directions with examples from the Rio Grande rift zone and other cratonic rifts. Over time periods of millions of years, periods of rotating regional stress fi elds are marked by a lull in magmatic activity and a temporary halt to tectonic rift opening. Admittedly, rifting cycle comparisons are biased by the short time scale of global seismic and geodetic measurements, which span a small fraction of the 10 2 -10 5 year rifting cycle. Within rift sectors with upper crustal magma chambers beneath the central rift valley (e.g., Main Ethiopian, Afar, and Eastern or Gregory rifts) seismic energy release accounts for a small fraction of the deformation; most of the strain is accommodated by magma intrusion and slowslip. Magma intrusion processes appear to decrease the time period between rifting episodes, effectively accelerating the rift to rupture process. Thus, the inter-seismic period in rift zones with crustal magma reservoirs is strongly dependent upon the

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Post‐Rift Deformation of the North East and South Atlantic Margins: Are “Passive Margins” Really Passive?

Cited by 6 publications

References 49 publications

Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins

Stratigraphic landscape analysis, thermochronology and the episodic development of elevated, passive continental margins

The chronology and tectonic style of landscape evolution along the elevated Atlantic continental margin of South Africa resolved by joint apatite fission track and (U‐Th‐Sm)/He thermochronology

The time scales of continental rifting: Implications for global processes

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