scholarly journals Continental-scale geographic change across Zealandia during Paleogene subduction initiation

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 419-424 ◽  
Author(s):  
R. Sutherland ◽  
G.R. Dickens ◽  
P. Blum ◽  
C. Agnini ◽  
L. Alegret ◽  
...  
Keyword(s):  
New Caledonia ◽  
Plate Motion ◽  
Mantle Flow ◽  
Vertical Movements ◽  
Subduction Initiation ◽  
Continental Scale ◽  
The North ◽  
Elevation Changes ◽  
International Ocean Discovery Program ◽  
Tectonic Forces

Abstract Data from International Ocean Discovery Program (IODP) Expedition 371 reveal vertical movements of 1–3 km in northern Zealandia during early Cenozoic subduction initiation in the western Pacific Ocean. Lord Howe Rise rose from deep (∼1 km) water to sea level and subsided back, with peak uplift at 50 Ma in the north and between 41 and 32 Ma in the south. The New Caledonia Trough subsided 2–3 km between 55 and 45 Ma. We suggest these elevation changes resulted from crust delamination and mantle flow that led to slab formation. We propose a “subduction resurrection” model in which (1) a subduction rupture event activated lithospheric-scale faults across a broad region during less than ∼5 m.y., and (2) tectonic forces evolved over a further 4–8 m.y. as subducted slabs grew in size and drove plate-motion change. Such a subduction rupture event may have involved nucleation and lateral propagation of slip-weakening rupture along an interconnected set of preexisting weaknesses adjacent to density anomalies.

An analytical model concerning the possible initiation of subduction between the India and Africa plates, caused by the Morondova plume

2020 ◽  
Author(s):  
Bernhard Steinberger ◽  
Douwe van Hinsbergen
Keyword(s):  
Subduction Zones ◽  
Plate Tectonics ◽  
Eastern Mediterranean ◽  
Plate Boundary ◽  
Plate Motion ◽  
Mantle Flow ◽  
Plate Motions ◽  
Subduction Initiation ◽  
Euler Pole ◽  
Geodynamic Processes

<p>Identifying the geodynamic processes that trigger the formation of new subduction zones is key to understand what keeps the plate tectonic cycle going, and how plate tectonics once started. Here we discuss the possibility of plume-induced subduction initiation. Previously, our numerical modeling revealed that mantle upwelling and radial push induced by plume rise may trigger plate motion change, and plate divergence as much as 15-20 My prior to LIP eruption. Here we show that, depending on the geometry of plates, the distribution of cratonic keels and where the plume rises, it may also cause a plate rotation around a pole that is located close to the same plate boundary where the plume head impinges: If that occurs near one end of the plate boundary, an Euler pole of the rotation may form along that plate boundary, with extension on one side, and convergence on the other.  This concept is applied to the India-Africa plate boundary and the Morondova plume, which erupted around 90 Ma, but may have influenced plate motions as early as 105-110 Ma. If there is negligible friction, i.e. there is a pre-existing weak plate boundary, we estimate that the total amount of convergence generated in the northern part of the India-Africa plate boundary can exceed 100 km, which is widely thought to be sufficient to initiate forced, self-sustaining subduction. This may especially occur if the India continental craton acts like an “anchor” causing a comparatively southern location of the rotation pole of the India plate. Geology and paleomagnetism-based reconstructions of subduction initiation below ophiolites from Pakistan, through Oman, to the eastern Mediterranean reveal that E-W convergence around 105 Ma caused forced subduction initiation, and we tentatively postulate that this is triggered by Morondova plume head rise. Whether the timing of this convergence is appropriate to match observations on subduction initiation as early as 105 Ma depends on the timing of plume head arrival, which may predate eruption of the earliest volcanics. It also depends on whether a plume head already can exert substantial torque on the plate while it is still rising – for example, if the plate is coupled to the induced mantle flow by a thick craton.</p>

Analysis of geological hiatus surfaces across Africa in the Cenozoic and implications for the timescales of convectively-maintained topography

2019 ◽  
Vol 56 (12) ◽  
pp. 1333-1346 ◽  
Author(s):  
Sara Carena ◽  
Hans-Peter Bunge ◽  
Anke M. Friedrich
Keyword(s):  
Vertical Motion ◽  
High Elevation ◽  
Mantle Flow ◽  
Continental Scale ◽  
Proxy Records ◽  
Geological Maps ◽  
Geodynamic Processes ◽  
Elevation Changes ◽  
History Of ◽  
Temporal And Spatial

Geological maps are a powerful but underutilized tool for constraining geodynamic processes and models. Unraveling the Cenozoic elevation history of Africa and distinguishing between competing uplift and subsidence scenarios is of considerable interest to constrain the dynamic processes in the mantle beneath the continent. Here, we explore continental-scale geological maps, and map temporal and spatial patterns of geological contacts, assuming that interregional-scale unconformable contacts (hiatus surfaces) on geological maps yield proxy records of paleotopography and vertical motion. We found that significant differences in the spatial extents of interregional-scale hiatus surfaces exist across Africa at the timescale of geologic series. A significant expansion of total unconformable area at the base of the Miocene strongly suggests that the Oligocene was a period of uplift in most of Africa. In southern Africa there is a complete absence of marine sediments in both the Oligocene and Pleistocene. This pattern suggests that southernmost Africa reached a high elevation in the Oligocene, subsided in the Miocene–Pliocene, and has been high again since the latest Pliocene or Pleistocene. Our hiatus mapping results support a dynamic origin of Africa’s topography. In particular, they point to elevation changes at the timescale of geologic series (ten to a few tens of millions of years), which is considerably smaller than the mantle transit time. The timescale for elevation changes in Africa is, thus, comparable with the rapid spreading in the South Atlantic, which have been geodynamically linked to African elevation changes through pressure-driven upper mantle flow.

Progress in observational geodynamics from the analysis of geological hiatus surfaces across Africa in the Cenozoic

2020 ◽  
Author(s):  
Hans-Peter Bunge ◽  
Sara Carena ◽  
Anke M. Friedrich
Keyword(s):  
Upper Mantle ◽  
Spreading Rate ◽  
Mantle Flow ◽  
Dynamic Topography ◽  
Geologic Time ◽  
Continental Scale ◽  
Geological Maps ◽  
Elevation Changes ◽  
Crucial Information ◽  
Geodynamic Models

<p>Geological maps contain crucial information to constrain geodynamic models, but they remain underutilized by the geodynamic community. Particularly significant are unconformable geologic contacts at continental scales: what is usually perceived as a lack of data (material eroded or not deposited) becomes instead part of the signal of dynamic topography variation over geologic time.</p><p> </p><p> Here we show how we were able to use geological maps to constrain the dynamic processes in the mantle beneath Africa by understanding its Cenozoic elevation history, and by using it to distinguish between different uplift and subsidence scenarios. This was accomplished by using geological maps at the continent scale to map the spatiotemporal patterns of geological contacts, under the assumption that continental-scale unconformable contacts are proxies for vertical motions and paleotopography.</p><p> </p><p>We found that significant differences exist in interregional-scale hiatus surfaces at the level of geologic series. The total unconformable area at the base of the Miocene expands significantly compared to the base of the Oligocene, strongly suggesting that most of Africa underwent uplift in the Oligocene. In southern Africa there are no marine Oligocene or Pleistocene sediments, suggesting that this region reached a high in the Oligocene, subsided in the Miocene and Pliocene, and has been high again since late Pliocene to Pleistocene. Our results therefore support a dynamic origin for the topography of Africa. Specifically, the time-scale of geologic series (at most a few tens of millions of years) is comparable to the spreading-rate variations in the south Atlantic, which have been linked to African elevation changes through pressure-driven upper mantle flow.</p>

A review of the tectonics of the northern Middle East region

1984 ◽  
Vol 121 (6) ◽  
pp. 577-587 ◽  
Author(s):  
P. E. R. Lovelock
Keyword(s):  
Late Cretaceous ◽  
Kinematic Model ◽  
Continental Collision ◽  
Dead Sea ◽  
Plate Motion ◽  
Arabian Plate ◽  
Southern Boundary ◽  
The North ◽  
The Dead ◽  
Two Stages

AbstractThe structure of the northern part of the Arabian platform is reviewed in the light of hitherto unpublished exploration data and the presently accepted kinematic model of plate motion in the region. The Palmyra and Sinjar zones share a common history of development involving two stages of rifting, one in the Triassic–Jurassic and the other during late Cretaceous to early Tertiary times. Deformation of the Palmyra zone during the Mio-Pliocene is attributed to north–south compression on the eastern block of the Dead Sea transcurrent system which occurred after continental collision in the north in southeast Turkey. The asymmetry of the Palmyra zone is believed to result from northward underthrusting along the southern boundary facilitated by the presence of shallow Triassic evaporites. An important NW-SE cross-plate shear zone has been identified, which can be traced for 600 km and which controls the course of the River Euphrates over long distances in Syria and Iraq. Transcurrent motion along this zone resulted in the formation of narrow grabens during the late Cretaceous which were compressed during the Mio-Pliocene. To a large extent, present day structures in the region result from compressional reactivation of old lineaments within the Arabian plate by the transcurrent motion of the Dead Sea fault zone and subsequent continental collision.

Fractures in the northern plains, stream patterns, and the midcontinent stress field

1987 ◽  
Vol 24 (6) ◽  
pp. 1086-1097 ◽  
Author(s):  
Mel R. Stauffer ◽  
Don J. Gendzwill
Keyword(s):  
Stress Field ◽  
Horizontal Stress ◽  
The Body ◽  
North American Plate ◽  
Plate Motion ◽  
Viscous Drag ◽  
Near Surface ◽  
The North ◽  
Elastic Rebound ◽  
Western North Dakota

Fractures in Late Cretaceous to Late Pleistocene sediments in Saskatchewan, eastern Montana, and western North Dakota form two vertical, orthogonal sets trending northeast–southwest and northwest–southeast. The pattern is consistent, regardless of rock type or age (except for concretionary sandstone). Both sets appear to be extensional in origin and are similar in character to joints in Alberta. Modem stream valleys also trend in the same two dominant directions and may be controlled by the underlying fractures.Elevation variations on the sub-Mannville (Early Cretaceous) unconformity form a rectilinear pattern also parallel to the fracture sets, suggesting that fracturing was initiated at least as early as Late Jurassic. It may have begun earlier, but there are insufficient data at present to extend the time of initiation.We interpret the fractures as the result of vertical uplift together with plate motion: the westward drift of North America. The northeast–southwest-directed maximum principal horizontal stress of the midcontinent stress field is generated by viscous drag effects between the North American plate and the mantle. Vertical uplift, erosion, or both together produce a horizontal tensile state in near-surface materials, and with the addition of a directed horizontal stress through plate motion, vertical tension cracks are generated parallel to that horizontal stress (northeast–southwest). Nearly instantaneous elastic rebound results in the production of second-order joints (northwest–southeast) perpendicular to the first. In this manner, the body of rock is being subjected with time to complex alternation of northeast–southwest and northwest–southeast horizontal stresses, resulting in the continuous and contemporaneous production of two perpendicular extensional joint sets.

REPEATED TRENDS OF FOLDS AND CROSS-FOLDS IN PALAEOZOIC ROCKS, PARRSBORO, NOVA SCOTIA

1964 ◽  
Vol 1 (3) ◽  
pp. 167-183 ◽  
Author(s):  
W. K. Fyson
Keyword(s):  
Nova Scotia ◽  
Vertical Movements ◽  
Clastic Rocks ◽  
Three Generations ◽  
The North ◽  
North Side ◽  
Two Generations ◽  
Major Fault ◽  
Granitic Intrusions ◽  
Middle Carboniferous

On the north side of a major fault three generations of folds F1, F2, F3 affect pre-Carboniferous phyllites; south of the fault two generations, C1, C2, affect middle Carboniferous clastic rocks. The F1 folds are isoclinal and obscure. The main folds, F2 in the phyllites and C1 in the Carboniferous rocks, trend east-northeast parallel to the fault. F2 are overturned southward and C1 northward, both toward the fault. Cross-folds, F3 in the phyllites and C2 in the Carboniferous rocks, trend northnortheast. Steeply plunging F3 and C2 are asymmetric and Z-shaped in plan profile.The F2 folds in the phyllites, though similar in geometry to folds in the middle Carboniferous rocks, appear, like F1 and F2, to have formed prior to the middle Carboniferous. This is indicated by the occurrence of unfolded Devonian(?) granitic intrusions crossing F3 folds, and a few miles north of the major fault, by middle Carboniferous rocks lying unconformably- above similar intrusions.One possible explanation for the repeated trends, which also accounts for the sense of overturning and asymmetry of the folds, relates the folding to alternating vertical and horizontal movements along the major fault. The vertical movements were followed by gravity sliding toward the fault to produce the main folds, and the horizontal movements, repeatedly dextral in sense, resulted in the Z-shaped cross-folds.

Redescription of Pseudogilquinia pillersi (Southwell, 1929) (Cestoda, Trypanorhyncha) from serranid and lethrinid fishes from New Caledonia and Australia

2007 ◽  
Vol 52 (3) ◽  
Author(s):  
Ian Beveridge ◽  
Claude Chauvet ◽  
Jean-Lou Justine
Keyword(s):  
Sri Lanka ◽  
Host Range ◽  
East Coast ◽  
New Caledonia ◽  
Epinephelus Coioides ◽  
North East ◽  
The North ◽  
Specific Variation ◽  
Epinephelus Malabaricus

AbstractPseudogilquinia pillersi (Southwell, 1929), a poorly known species of trypanorhynch, is redescribed from plerocerci collected from Epinephelus coioides (Hamilton, 1922), Epinephelus malabaricus (Bloch et Schneider, 1801) (Serranidae) and Plectropomus laevis (Lacépède, 1801) (Serranidae) off New Caledonia. These were compared with specimens from Lethrinus atkinsoni Seale, 1910 and Lethrinus miniatus (Forster, 1801) (Lethrinidae) off the north-east coast of Australia as well as syntypes from Protonibea diacantha (Lacépède, 1802) from Sri Lanka. Although size differences were found in parts of the scolex as well as in the sizes of the tentacular hooks, the hook arrangements were identical in all specimens. The differences observed were attributed provisionally to intra-specific variation across a wide geographic and host range.

scholarly journals Speedup and fracturing of George VI Ice Shelf, Antarctic Peninsula

2013 ◽  
Vol 7 (3) ◽  
pp. 797-816 ◽  
Author(s):  
T. O. Holt ◽  
N. F. Glasser ◽  
D. J. Quincey ◽  
M. R. Siegfried
Keyword(s):  
Antarctic Peninsula ◽  
Structural Changes ◽  
Surface Elevation ◽  
Ice Shelf ◽  
Ice Shelves ◽  
The North ◽  
Surface Elevation Change ◽  
Elevation Changes ◽  
Negative Surface ◽  
The Antarctic

Abstract. George VI Ice Shelf (GVIIS) is located on the Antarctic Peninsula, a region where several ice shelves have undergone rapid breakup in response to atmospheric and oceanic warming. We use a combination of optical (Landsat), radar (ERS 1/2 SAR) and laser altimetry (GLAS) datasets to examine the response of GVIIS to environmental change and to offer an assessment on its future stability. The spatial and structural changes of GVIIS (ca. 1973 to ca. 2010) are mapped and surface velocities are calculated at different time periods (InSAR and optical feature tracking from 1989 to 2009) to document changes in the ice shelf's flow regime. Surface elevation changes are recorded between 2003 and 2008 using repeat track ICESat acquisitions. We note an increase in fracture extent and distribution at the south ice front, ice-shelf acceleration towards both the north and south ice fronts and spatially varied negative surface elevation change throughout, with greater variations observed towards the central and southern regions of the ice shelf. We propose that whilst GVIIS is in no imminent danger of collapse, it is vulnerable to ongoing atmospheric and oceanic warming and is more susceptible to breakup along its southern margin in ice preconditioned for further retreat.

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