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Journal Article•DOI•

Tectonics of the Dalrymple Trough and uplift of the Murray Ridge (NW Indian Ocean)

Mathieu Rodriguez1, Nicolas Chamot-Rooke1, Philippe Huchon2, Philippe Huchon3, Marc Fournier2, Marc Fournier3, Siegfried Lallemant4, Matthias Delescluse1, Sébastien Zaragosi5, Nicolas Mouchot •
École Normale Supérieure1, University of Paris2, Indiana Statewide Testing for Educational Progress-Plus3, Cergy-Pontoise University4, University of Bordeaux5
01 Dec 2014-Tectonophysics (Elsevier)-Vol. 636, pp 1-17
TL;DR: The Dalrymple Trough is a 150km-long basin located at the northern termination of the Owen Fracture Zone (OFZ), which is the present-day active India-Arabia plate boundary as mentioned in this paper.
About: This article is published in Tectonophysics.The article was published on 2014-12-01 and is currently open access. It has received 21 citations till now. The article focuses on the topics: Trough (geology) & Fracture zone.

Summary (4 min read)

Jump to: [1. Introduction] – [2.1. Morphology and structure of the Dalrymple Trough and the Murray Ridge] – [2.2. Geological history] – [2.3. Regional unconformities in the Arabian Sea] – [2.4. The Indus deep-sea fan] – [3. Material and Methods] – [4.1. Criteria for the identification of sedimentary deposits] – [4.2. Sedimentation rates] – [6. Age estimates of the deformation] – [7.1. Mode of opening of the south Dalrymple Trough] – [7.2. Tectonic history of the Dalrymple Trough-Murray Ridge system] and [8. Conclusions and perspectives]

1. Introduction

  • The Dalrymple Trough consists of a series of basins forming the present-day loose boundary between India and Arabia plates in the Arabian Sea, connecting the pure dextral strike-slip Owen Fracture Zone (OFZ hereafter) to the sinistral Ornach-Nal Fault Zone in Pakistan (Fig. 1; McKenzie and Sclater, 1971; Minshull et al., 1992).
  • Seismicity along the entire India-Arabia boundary is scarce, but the strongest magnitude event (Mw=5.8) has been recorded in the Dalrymple Trough (Fig. 2) (Quittmeyer and Kafka, 1984; Gordon and DeMets, 1989; Fournier et al., 2001).
  • Few active horsetail terminations have been documented so far in deep-sea environments.
  • The origin of the M-unconformity in the Oman abyssal plain is revised in the light of this new tectonic framework.
  • The first objective of this study is to understand how rifting took place in the Dalrymple Trough, and subsequently evolved into a large and complex stepover basin.

2.1. Morphology and structure of the Dalrymple Trough and the Murray Ridge

  • The Dalrymple Trough is divided into two main segments (Edwards et al., 2000).
  • The southern part of the Dalrymple Trough abruptly ends at the Jinnah High at ~23°N (Burgath et al., 2002), which is formed by the tilt of the Indus deposits of the Oman abyssal plain (Ellouz-Zimmerman et al., 2007a,b).
  • The northern Murray Ridge (between 23°N and 23°40'N) forms a normal faulted horst with a more subtle topographic expression than the southern segment (about 1000-m high with respect to the surrounding seafloor, Fig. 1).
  • The pure strike-slip or transtensive character of a stepover basin depends on the colinearity between the direction of relative motion and that of the strike slip fault (Wu et al., 2009).
  • Because the Dalrymple Trough deviates from the small circle defined by Fournier et al. (2011) (Fig. 2), the structure is considered as transtensive, in agreement with focal mechanisms of earthquakes.

2.2. Geological history

  • Buried, abrupt and sharp vertical fault offsets recognized on the eastern side of the Southern Murray Ridge (Edwards et al., 2000) could correspond to the northward prolongation of the fracture zone that used to form the Miocene India-Arabia plate boundary (Fig. 3).
  • As attested by Paleogene hemipelagites recognized on their top (Shipboard Scientific Party, 1989; Gaedicke et al., 2002a,b), the Owen and Murray Ridges were part of a series of bathymetric highs formed in Paleocene-Early Eocene times (Fig.1, 3) and subsequently rejuvenated during Neogene times.
  • Two regional angular unconformities, “U” and “M”, mark the episodes of uplift and subsidence.
  • Understanding the signification of these unconformities is critical to the understanding of the formation of the Dalrymple Trough and Murray ridge, and how it relates with the history of the OFZ.

2.3. Regional unconformities in the Arabian Sea

  • The U-unconformity does not have a tectonic origin, and simply reflects the transition from Oligocene pelagites to Lower Miocene turbidites as the substratum of the Owen Ridge gets progressively buried under the Indus deep-sea fan (Shipboard Scientific Party, 1989; Mountain and Prell, 1990).
  • Ma at ODP Site 730 (Rodriguez et al., 2014) consistent with the age of the unconformity marking the uplift of the Southern Murray Ridge.
  • This unconformity has never been drilled, which results in strong uncertainties in its age (Schlüter et al., 2002).
  • First related to a Messinian uplift event in the Zagros Mountain (Ross et al., 1986), it has also been related to the onset of seafloor spreading in the Gulf of Aden (Schlüter et al., 2002), estimated at 13 Ma when these studies were published (Cochran, 1981).

2.4. The Indus deep-sea fan

  • Tectonic deformation along the India-Arabia plate-boundary is well recorded by sediments belonging to the Indus turbiditic system.
  • At its thickest part the fan is more than 9-km thick, but its thickness decreases when approaching the Owen-Murray Ridge (Fig. 3c) (Coumes and Kolla, 1984; Clift et al., 2001).
  • It forms a typical mud-rich, “passive margin fan” (sensu Reading and Richards, 1994), with numerous inter-bedded pelagic layers (Shipboard Scientific Party, 1989).
  • Indus Fan sedimentation started during the Middle Eocene as the result of the onset of the India-Eurasia collision and accelerated since the Early Miocene, coincident with a sharp increase in sedimentation rates related to the uplift of the Himalaya and the onset of the Asian monsoon (Clift et al., 2001; Clift and Gaedicke, 2002(!.

3. Material and Methods

  • The new dataset presented in this study was acquired onboard the French Navy oceanographic vessel Beautemps-Beaupré during the OWEN1 and 2 (2009 and 2012) surveys.
  • Multibeam bathymetry was collected using a Kongsberg-Simrad EM 120 echosounder (Fig. 2), and combined with previously published data acquired during the MARABIE (Bourget et al., 2010) and CHAMAK cruises (EllouzZimmerman et al., 2007a,b).
  • The processing consisted in geometry setting, water-velocity normal moveout, stacking, water-velocity F-k domain post-stack time migration, bandpass filtering and automatic gain control.
  • Two-way travel time to seismic reflectors was converted to depth using a P-wave velocity between 1530 and 1730 m. s -1 for lower and upper bounds.
  • In the following, sedimentary series before the opening of the Dalrymple Trough are referred to as the “substratum” of the Dalrymple Trough, which is employed in the sense of “pre-rift” series, in order to avoid the confusion with the continental basement of the Murray Ridge observed on several profiles.

4.1. Criteria for the identification of sedimentary deposits

  • Turbiditic channels are characterized on seismic profiles by a typical lens-like architecture with a concave-up lower boundary, and discontinuous, high amplitude reflection.
  • The associated levees display a wedge shape, with high amplitude, transparent seismic facies.
  • Mass transport deposits display the same chaotic to transparent seismic facies, but their geometry is more irregular.
  • It is sometimes difficult to discriminate between turbiditic and pelagic deposits on seismic profiles.
  • Figure 5 summarizes the main criteria of sedimentary deposits identification.

4.2. Sedimentation rates

  • During turbiditic deposition (Late Miocene-Pliocene), the sedimentation rates ranged between 350 and 600 m Ma-1 according to estimations at DSDP Site 222 located at the edge of the OFZ (Fig. 1; latitude ~20°N) (Shipboard Scientific Party, 1974).
  • The authors estimate different pelagic thicknesses using P wave velocities ranging between 1550 and 1730 m.s-1 (table 1).
  • The second source of uncertainty is the regional variability of sedimentation rates, ranging between 30m.

6. Age estimates of the deformation

  • Opening of the Dalrymple Trough, Northern Murray Ridge uplift, and M-unconformity.
  • The syncline basin forming the trough displays a seismic facies typical of a turbiditic and pelagic layers succession (Fig. 6, 7).
  • This change in dip is due to the progressive transition from pelagic to turbiditic deposits as the Makran turbiditic system progressively buries the M-unconformity.

7.1. Mode of opening of the south Dalrymple Trough

  • The main structural characteristic of the Dalrymple Trough is the numerous transverse faults that form the horsetail structure.
  • The full connection of the strike-slip fault with the transverse normal faults implies a large amount of relative motion in the model, which contrasts with the case of the Dalrymple Trough, where only ~5-10 km of relative motion were accommodated since the first stages of opening ~1.9 ± 0.9 Ma.
  • This raises the question of the relationship between the size of a basin and the amount of finite motion.
  • Moreover, the opening of the Dalrymple Trough enhanced the uplift of its flanks, and rejuvenated the topography at the northern Murray Ridge and the westernmost part of the southern Murray Ridge, similar to what is observed along the Dead Sea flanks (Basile and Allemand, 2002).

7.2. Tectonic history of the Dalrymple Trough-Murray Ridge system

  • The alternative involves a third, intermediate episode, in which the OFZ emplaced at ~6 Ma, and then underwent opening of stepover basins at 1.9 ± 0.9 Ma.
  • This framework, summarized in Figure 13, contrasts with the two stages history (in the Early and the Late Miocene) previously assessed (Gaedicke et al., 2002), and implies a new geodynamic interpretative scheme of the Dalrymple Trough-Murray Ridge system.
  • Origin of the ~8-10 Ma-old compressional episode of deformation.
  • The compressive deformation at the India-Arabia plate boundary probably results from complex tectonic interactions between both plates.

8. Conclusions and perspectives

  • This study documents a Late Miocene compressive episode along the India-Arabia plate boundary expressed by a complex set of folds at the connection between the OFZ and the Dalrymple Trough.
  • This age is significantly younger than the Miocene age previously proposed (Gaedicke et al., 2002) and in better agreement with the recent age of the OFZ, which shows no structure older than 3 Ma along strike (Rodriguez et al., 2011; 2013).
  • The last structural reorganization marked by the M-unconformity is roughly coeval with the opening of the Dead Sea Basin along the Levant Fault (TenBrink et al., 1989).
  • Deep-sea drillings would be useful to decipher the precise timing of the deformation in the area and confirms the link with monsoon intensity.
  • Second, the uplift of the northern Murray Ridge since ~1.9 ± 0.9 Ma might account for the Pleistocene southwestward migration of the Indus canyon on the Indian Margin (Kolla and Coumes, 1987).

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Geological Society of America Bulletin

[...]

Richard G. Hoy, Kenneth D. Ridgway
01 Jan 1997
TL;DR: In this paper, structural, sedimentological, and provenance data from the east-central flank of the Bighorn Mountains were used to study the development of footwall growth synclines, the evolution of fault-related folds, and the erosional unroofing history of intraforeland uplifts.
Abstract: Structural, sedimentological, and provenance data from Paleogene synorogenic deposits of the east-central flank of the Bighorn Mountains provide new information about the development of footwall growth synclines, the evolution of fault-related folds, and the erosional unroofing history of intraforeland uplifts. Three conglomerate units, the upper conglomerate member of the Fort Union Formation and the Kingsbury and Moncrief Members of the Wasatch Formation, are incorporated within an asymmetric, east-verging growth syncline in the footwall of the main range-bounding thrust system. Three stages of footwall deformation are recorded within these conglomerates. Analysis of mapped progressive unconformities, retrodeformed balanced cross sections, and conglomerate clast composition data define these stages as part of a continuum of deformation associated with the development of footwall growth synclines. Development of an anticline-syncline pair marked the earliest stage of growth syncline formation (stage I). Rotation of the shared fold limb resulted in amplification of the growth syncline. Fine-grained, synorogenic sediment derived from easily eroded Mesozoic mudstone bypassed the growth syncline during this stage. By the end of Lebo Shale deposition, an average of 12.1% of shortening and 6.46 km of uplift had occurred along the range margin. Continued growth syncline development was marked by the deposition of the Kingsbury Conglomerate. The Kingsbury Conglomerate was derived from resistant, middle and lower Paleozoic carbonate strata in the uplifted source terrane. Intraformational unconformities, recording as much as 55° of bed rotation, were developed within the Kingsbury Conglomerate as fold limb rotation occurred coeval with deposition. Cross sections indicate that during this early stage of fault-related folding, an average of 16.9% shortening and 8.12 km of uplift occurred along the eastern flank of the Bighorn Mountains (end of stage I). The intermediate stage (stage II) of footwall growth syncline development involved partial truncation of the growth syncline by the advancing thrust faults and deposition of the Moncrief Conglomerate. The lower portion of the Moncrief Conglomerate was rotated basinward in the developing growth syncline. The final stage of deformation (stage III) was dominated by the thrust faulting of middle and lower Paleozoic strata eastward over steeply dipping Mesozoic strata and rotated Eocene synorogenic conglomerate. During this stage of deformation, the Moncrief Conglomerate was deformed, as the initially blind thrusts propagated into the near-surface conglomerate deposits, truncated the entire footwall syncline, and overrode the synorogenic conglomerate package. Cross sections in areas where this final stage of deformation is well developed indicate that an average of 24.1% shortening and 9.7 km of uplift had occurred along the eastern margin of the Bighorn Mountains. The caliber of synorogenic deposition in the Powder River basin was linked directly to the lithologic composition of the Bighorn Mountains. Approximately half of the 3.6-km-thick source-stratigraphic section of the eastern Bighorn Mountains was eroded prior to accumulation of conglomerate. The majority of this eroded material was derived from Mesozoic mudstone and poorly indurated sandstone that were incapable of generating coarse detritus. The first Paleogene conglomerates deposited along the east-central Bighorn Mountains, therefore, do not represent the initiation of Laramide uplift, but instead represent the exposure of coarse-clast–forming rock types from the lower half of the hanging-wall stratigraphic section (i.e., the Mississippian Madison Limestone and Ordovician Bighorn Dolomite).

154 citations

Early (pre-8 Ma) Fault Activity and Temporal Strain Accumulation in the Central Indian Ocean

[...]

Jonathan M. Bull, K. S. Krishna, R.A. Scrutton
01 Dec 2008
TL;DR: In this article, the authors used seismic reflection data from seismic-reflection profiles within the central Indian Ocean to demonstrate that compressional activity started much earlier than previously thought, at around 15.4-13.9 Ma.
Abstract: The diffuse deformation zone in the central Indian Ocean is the classical example of distributed deformation of the oceanic lithosphere, where shortening between the Indian and Capricorn plates is manifest as reverse faulting (5–10-km-spaced faults) and long-wavelength (100–300 km) folding. The onset of this deformation is commonly regarded as a key far-field indicator for the start of major uplift of the Himalayas and Tibet, some 4000 km further to the north, due to increased deviatoric stresses within the wider India-Asia area. There has been disagreement concerning the likely timing for the onset of deformation between plate-motion inversions and seismic reflection–based studies. In the present study, fault displacement data from seismic-reflection profiles within the central Indian Ocean demonstrate that compressional activity started much earlier than previously thought, at around 15.4–13.9 Ma. From reconstructions of fault activity histories, we show that 12% of the total reverse fault population had been activated, and 14% of the total strain accumulated, prior to a sharp increase in the deformation rate at 8.0–7.5 Ma. There is no evidence for any regional unconformity before 8.0–7.5 Ma; early shortening was accommodated by activity on single isolated fault blocks. Total strain estimates derived are more variable and complex than those predicted from plate inversion, and they do not show simple west to east increase.

36 citations

Journal Article•DOI•
Unfolding impacts of freaky tectonics on sedimentary sequences along passive margins: Pioneer findings from western Indian continental margin (Offshore Indus Basin)

[...]

Majid Khan1, Ahmed Abdelmaksoud2•
University of Science and Technology Beijing1, Assiut University2
01 Sep 2020-Marine and Petroleum Geology
TL;DR: In this paper, the authors present a multidisciplinary study on Offshore Indus Basin (OIB) that is less investigated compared to adjacent marginal basins along the Western Passive Continental Margin of the Indian Plate (WCMI) serving as an elegant laboratory for understanding the synsedimentary rift-drift tectonics preserving a variety of episodic structural deformations and complex sedimentary infill.

20 citations

Journal Article•DOI•
Structure of the Offshore Obducted Oman Margin: Emplacement of Semail Ophiolite and Role of Tectonic Inheritance

[...]

Dia Ninkabou1, Dia Ninkabou2, Philippe Agard1, C. Nielsen2, Jeroen Smit3, Christian Gorini1, Mathieu Rodriguez4, Bilal U. Haq5, Bilal U. Haq1, Nicolas Chamot-Rooke4, Christian Weidle6, Céline Ducassou •
University of Paris1, Total S.A.2, Utrecht University3, École Normale Supérieure4, Smithsonian Institution5, University of Kiel6
01 Feb 2021-Journal of Geophysical Research

18 citations

Journal Article•DOI•
Tracking the paleogene India-Arabia plate boundary

[...]

Mathieu Rodriguez1, Philippe Huchon2, Philippe Huchon3, Nicolas Chamot-Rooke1, Marc Fournier3, Marc Fournier2, Matthias Delescluse1, Thomas François2, Thomas François3 •
École Normale Supérieure1, University of Paris2, Indiana Statewide Testing for Educational Progress-Plus3
01 Apr 2016-Marine and Petroleum Geology
TL;DR: In this paper, a seismic dataset crossing the Owen Fracture Zone, the Owen Basin, and the Oman Margin was acquired to track the past locations of the India-Arabia plate boundary.

16 citations

Cites background or methods or result from "Tectonics of the Dalrymple Trough a..."

  • ...The Owen Ridge uplifted later, in Late Miocene times, and is unrelated to any major migration of the India-Arabia boundary....

    [...]

  • ...Consistently, there is no tectonic activity in the Owen Basin and the Oman margin during the Late Eocene-Late Miocene time span....

    [...]

  • ...However, subsequent works (see section 3.3) showed that the Masirah Ophiolites are composed of Tithonian oceanic crust (Peters and Mercolli, 1998) and that the Owen Ridge uplifted in Late Miocene without any major migration of the IndiaArabia boundary (Rodriguez et al., 2014a, b)....

    [...]

  • ...This is in agreement with the Pliocene age of the OFZ, which is a much younger generation of the India-Arabia plate boundary than the Chain Fracture Zone (Fournier et al., 2008, 2011; Rodriguez et al., 2011, 2013b, 2014b)....

    [...]

  • ...4) Seismic profiles document the inception of transformmotion on the eastern side of the Owen Ridge at least 20 Ma, and indicate a narrow strike-slip boundary (Rodriguez et al., 2014a)....

    [...]

References
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Journal Article•DOI•
Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions

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Charles DeMets, Richard G. Gordon, Donald F. Argus, Seth Stein
01 Oct 1994-Geophysical Research Letters
TL;DR: In this article, the optimal recalibration of NUVEL-1 is proposed to multiply the angular velocities by a constant, α, of 0.9562, which is a compromise among slightly different calibrations appropriate for slow, medium, and fast rates of seafloor spreading.
Abstract: Recent revisions to the geomagnetic time scale indicate that global plate motion model NUVEL-1 should be modified for comparison with other rates of motion including those estimated from space geodetic measurements. The optimal recalibration, which is a compromise among slightly different calibrations appropriate for slow, medium, and fast rates of seafloor spreading, is to multiply NUVEL-1 angular velocities by a constant, α, of 0.9562. We refer to this simply recalibrated plate motion model as NUVEL-1A, and give correspondingly revised tables of angular velocities and uncertainties. Published work indicates that space geodetic rates are slower on average than those calculated from NUVEL-1 by 6±1%. This average discrepancy is reduced to less than 2% when space geodetic rates are instead compared with NUVEL-1A.

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An Zhisheng1, John E. Kutzbach2, Warren L. Prell3, Stephen C. Porter4•
Chinese Academy of Sciences1, University of Wisconsin-Madison2, Brown University3, University of Washington4
03 May 2001-Nature
TL;DR: The results of a numerical climate-model experiment support the argument that the stages in evolution of Asian monsoons are linked to phases of Himalaya–Tibetan plateau uplift and to Northern Hemisphere glaciation.
Abstract: The climates of Asia are affected significantly by the extent and height of the Himalayan mountains and the Tibetan plateau1,2,3,4 Uplift of this region began about 50 Myr ago, and further significant increases in altitude of the Tibetan plateau are thought to have occurred about 10–8 Myr ago4,5, or more recently However, the climatic consequences of this uplift remain unclear Here we use records of aeolian sediments from China6,7 and marine sediments from the Indian8,9,10 and North Pacific oceans11 to identify three stages of evolution of Asian climates: first, enhanced aridity in the Asian interior and onset of the Indian and east Asian monsoons, about 9–8 Myr ago; next, continued intensification of the east Asian summer and winter monsoons, together with increased dust transport to the North Pacific Ocean11, about 36–26 Myr ago; and last, increased variability and possible weakening of the Indian and east Asian summer monsoons and continued strengthening of the east Asian winter monsoon since about 26 Myr ago The results of a numerical climate-model experiment, using idealized stepwise increases of mountain–plateau elevation, support the argument that the stages in evolution of Asian monsoons are linked to phases of Himalaya–Tibetan plateau uplift and to Northern Hemisphere glaciation

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Journal Article•DOI•
Geologically current plate motions

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Charles DeMets1, Richard G. Gordon2, Donald F. Argus3•
University of Wisconsin-Madison1, Rice University2, California Institute of Technology3
01 Apr 2010-Geophysical Journal International
TL;DR: MORVEL as discussed by the authors is a new closure-enforced set of angular velocities for the geologically current motions of 25 tectonic plates that collectively occupy 97 per cent of Earth's surface.
Abstract: SUMMARY We describe best-fitting angular velocities and MORVEL, a new closure-enforced set of angular velocities for the geologically current motions of 25 tectonic plates that collectively occupy 97 per cent of Earth's surface. Seafloor spreading rates and fault azimuths are used to determine the motions of 19 plates bordered by mid-ocean ridges, including all the major plates. Six smaller plates with little or no connection to the mid-ocean ridges are linked to MORVEL with GPS station velocities and azimuthal data. By design, almost no kinematic information is exchanged between the geologically determined and geodetically constrained subsets of the global circuit—MORVEL thus averages motion over geological intervals for all the major plates. Plate geometry changes relative to NUVEL-1A include the incorporation of Nubia, Lwandle and Somalia plates for the former Africa plate, Capricorn, Australia and Macquarie plates for the former Australia plate, and Sur and South America plates for the former South America plate. MORVEL also includes Amur, Philippine Sea, Sundaland and Yangtze plates, making it more useful than NUVEL-1A for studies of deformation in Asia and the western Pacific. Seafloor spreading rates are estimated over the past 0.78 Myr for intermediate and fast spreading centres and since 3.16 Ma for slow and ultraslow spreading centres. Rates are adjusted downward by 0.6–2.6 mm yr−1 to compensate for the several kilometre width of magnetic reversal zones. Nearly all the NUVEL-1A angular velocities differ significantly from the MORVEL angular velocities. The many new data, revised plate geometries, and correction for outward displacement thus significantly modify our knowledge of geologically current plate motions. MORVEL indicates significantly slower 0.78-Myr-average motion across the Nazca–Antarctic and Nazca–Pacific boundaries than does NUVEL-1A, consistent with a progressive slowdown in the eastward component of Nazca plate motion since 3.16 Ma. It also indicates that motions across the Caribbean–North America and Caribbean–South America plate boundaries are twice as fast as given by NUVEL-1A. Summed, least-squares differences between angular velocities estimated from GPS and those for MORVEL, NUVEL-1 and NUVEL-1A are, respectively, 260 per cent larger for NUVEL-1 and 50 per cent larger for NUVEL-1A than for MORVEL, suggesting that MORVEL more accurately describes historically current plate motions. Significant differences between geological and GPS estimates of Nazca plate motion and Arabia–Eurasia and India–Eurasia motion are reduced but not eliminated when using MORVEL instead of NUVEL-1A, possibly indicating that changes have occurred in those plate motions since 3.16 Ma. The MORVEL and GPS estimates of Pacific–North America plate motion in western North America differ by only 2.6 ± 1.7 mm yr−1, ≈25 per cent smaller than for NUVEL-1A. The remaining difference for this plate pair, assuming there are no unrecognized systematic errors and no measurable change in Pacific–North America motion over the past 1–3 Myr, indicates deformation of one or more plates in the global circuit. Tests for closure of six three-plate circuits indicate that two, Pacific–Cocos–Nazca and Sur–Nubia–Antarctic, fail closure, with respective linear velocities of non-closure of 14 ± 5 and 3 ± 1 mm yr−1 (95 per cent confidence limits) at their triple junctions. We conclude that the rigid plate approximation continues to be tremendously useful, but—absent any unrecognized systematic errors—the plates deform measurably, possibly by thermal contraction and wide plate boundaries with deformation rates near or beneath the level of noise in plate kinematic data.

2,089 citations

Journal Article•DOI•
Mantle dynamics, uplift of the Tibetan Plateau, and the Indian Monsoon

[...]

Peter Molnar, Philip England, Joseph Martinod
01 Nov 1993-Reviews of Geophysics
TL;DR: For example, Hou et al. as mentioned in this paper show that a small increase in the mean elevation of the Tibetan Plateau of 1000 m or more in a few million years is required by abrupt tectonic and environmental changes in Asia and the Indian Ocean.
Abstract: Convective removal of lower lithosphere beneath the Tibetan Plateau can account for a rapid increase in the mean elevation of the Tibetan Plateau of 1000 m or more in a few million years. Such uplift seems to be required by abrupt tectonic and environmental changes in Asia and the Indian Ocean in late Cenozoic time. The composition of basaltic volcanism in northern Tibet, which apparently began at about 13 Ma, implies melting of lithosphere, not asthenosphere. The most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere. The initiation of normal faulting in Tibet at about 8 (± 3) Ma suggests that the plateau underwent an appreciable increase in elevation at that time. An increase due solely to the isostatic response to crustal thickening caused by India's penetration into Eurasia should have been slow and could not have triggered normal faulting. Another process, such as removal of relatively cold, dense lower lithosphere, must have caused a supplemental uplift of the surface. Folding and faulting of the Indo-Australian plate south of India, the most prominent oceanic intraplate deformation on Earth, began between about 7.5 and 8 Ma and indicates an increased north-south compressional stress within the Indo-Australian plate. A Tibetan uplift of only 1000 m, if the result of removal of lower lithosphere, should have increased the compressional stress that the plateau applies to India and that resists India's northward movement, from an amount too small to fold oceanic lithosphere, to one sufficient to do so. The climate of the equatorial Indian Ocean and southern Asia changed at about 6–9 Ma: monsoonal winds apparently strengthened, northern Pakistan became more arid, but weathering of rock in the eastern Himalaya apparently increased. Because of its high altitude and lateral extent, the Tibetan Plateau provides a heat source at midlatitudes that should oppose classical (symmetric) Hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons. For the simple case of axisymmetric heating (no dependence on longitude) of an atmosphere without dissipation, theoretical analyses by Hou, Lindzen, and Plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal (monsoonlike) circulation than such a source centered on the equator, but only if heating exceeds a threshold whose level increases with the latitude of the heat source. Because heating of the atmosphere over Tibet should increase monotonically with elevation of the plateau, a modest uplift (1000–2500 m) of Tibet, already of substantial extent and height, might have been sufficient to exceed a threshold necessary for a strong monsoon. The virtual simultaneity of these phenomena suggests that uplift was rapid: approximately 1000 m to 2500 m in a few million years. Moreover, nearly simultaneously with the late Miocene strengthening of the monsoon, the calcite compensation depth in the oceans dropped, plants using the relatively efficient C4 pathway for photosynthesis evolved rapidly, and atmospheric CO2 seems to have decreased, suggesting causal relationships and positive feedbacks among these phenomena. Both a supplemental uplift of the Himalaya, the southern edge of Tibet, and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the Himalaya that, in turn, enhanced extraction of CO2 from the atmosphere. Thus these correlations offer some support for links between plateau uplift, a downdrawing of CO2 from the atmosphere, and global climate change, as proposed by Raymo, Ruddiman, and Froehlich. Mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts, but might also play an important role in altering regional and global climates.

1,753 citations

"Tectonics of the Dalrymple Trough a..." refers background in this paper

  • ...The increase in stress applied by the Miocene growth of the Himalayas on India's plate boundaries has been tentatively proposed as the driver for this plate reorganization event (Bull et al., 2010; Molnar and Stock, 2009; Molnar et al., 1993)....

    [...]

Journal Article•DOI•
Global Bathymetry and Elevation Data at 30 Arc Seconds Resolution: SRTM30_PLUS

[...]

J. J. Becker1, David T. Sandwell1, Walter H. F. Smith2, J. Braud3, B. Binder1, J. Depner3, D. Fabre3, J. Factor4, S. Ingalls4, S-H. Kim1, R. Ladner1, Karen M. Marks2, S. Nelson1, A. Pharaoh, R. Trimmer4, J. Von Rosenberg4, G. Wallace4, Pauline Weatherall5 •
Scripps Institution of Oceanography1, Silver Spring Networks2, Stennis Space Center3, National Geospatial-Intelligence Agency4, British Oceanographic Data Centre5
04 Nov 2009-Marine Geodesy
TL;DR: A 30-arc second resolution global topography/bathymetry grid (SRTM30_PLUS) has been developed from a wide variety of data sources as discussed by the authors, which is based on a new satellite-gravity model where the gravity-to-topography ratio is calibrated using 298 million edited soundings.
Abstract: A new 30-arc second resolution global topography/bathymetry grid (SRTM30_PLUS) has been developed from a wide variety of data sources. Land and ice topography comes from the SRTM30 and ICESat topography, respectively. Ocean bathymetry is based on a new satellite-gravity model where the gravity-to-topography ratio is calibrated using 298 million edited soundings. The main contribution of this study is the compilation and editing of the raw soundings, which come from NOAA, individual scientists, SIO, NGA, JAMSTEC, IFREMER, GEBCO, and NAVOCEANO. The gridded bathymetry is available for ftp download in the same format as the 33 tiles of SRTM30 topography. There are 33 matching tiles of source identification number to convey the provenance of every grid cell. The raw sounding data, converted to a simple common format, are also available for ftp download.

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Frequently Asked Questions (7)
Q1. What are the characteristics of turbiditic channels?

Turbiditic channels are characterized on seismic profiles by a typical lens-like architecture with a concave-up lower boundary, and discontinuous, high amplitude reflection. 

Considering a steady India-Arabia motion of 3±1 mm.yr-1 (Fournier et al. 2008a,b; 2011), the Dalrymple Trough opened in response to a limited amount of strike-slip motion, in the order of 5-10 km. 

The critical Coulomb wedge theory and geological studies (Berger et al., 2008; Whipple, 2009; Malavieille, 2010; Iaffaldano et al., 2011) suggest that major climate changes can affect the wedge taper at a regional scale, and induce widespread structural reorganization. 

Because the Dalrymple Trough deviates from the small circle defined by Fournier et al. (2011) (Fig. 2), the structure is considered as transtensive, in agreement with focal mechanisms of earthquakes. 

the onset of contourite deposition may reflect local disturbance of bottom currents following the opening of the basin (Rodriguez et al., 2013b). 

The age of abandonment of the youngest channel-levee is estimated by the thickness of the overlying pelagic cover, converted into time using uniform pelagic sedimentation rates in the area (30-55 m Ma -1 ). 

The last structural reorganization marked by the M-unconformity is roughly coeval with the opening of the Dead Sea Basin along the Levant Fault (TenBrink et al., 1989).