Thick shell tectonics on one‐plate planets: Applications to Mars

Banerdt, W. B.; Phillips, R. J.; Sleep, Norman H.; Saunders, R. S.

doi:10.1029/jb087ib12p09723

Cited by 121 publications

(146 citation statements)

References 32 publications

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“…Most authors have suggested that these radial graben systems are entirely tectonic features, although as noted in the literature multiple lithospheric deformation mechanisms are required to account for the observed distribution of the graben (Banerdt et al, 1982;Wilson and Head, 2002a). Specifically, the graben on the Tharsis rise itself are reasonably explained via isostatic models, although these models prohibit development of extensional features such as graben along the Tharsis flanks.…”

Section: Model Backgroundmentioning

confidence: 98%

Mangala Valles, Mars: Assessment of Early Stages of Flooding and Downstream Flood Evolution

2005

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Abstract. The Mangala Valles system is an~900 km fluvially carved channel system located southwest of the Tharsis rise and is unique among the martian outflow channels in that it heads at a linear fracture within the crust as opposed to a collapsed region of chaos as is the case with the circum-Chryse channels. Mangala Valles is confined within a broad, north-south trending depression, and begins as a single valley measuring up to 350 km wide that extends northward from a Memnonia Fossae graben, across the southern highlands toward the northern lowlands. Approximately 600 km downstream, this single valley branches into multiple channels, which ultimately lose their expression at the dichotomy boundary. Previous investigations of Mangala Vallis suggested that many of the units mapped interior to the valley were depositional, related to flooding, and that a minimum of two distinct periods of flooding separated by tens to hundreds of millions of years were required to explain the observed geology. We use infrared and visible images from the THermal EMission Imaging System (THEMIS), and topographic data from the Mars Orbiting Laser Altimeter (MOLA), to investigate the nature of the units mapped within Mangala Vallis. We find that the geomorphology of the units, as well as their topographic and geographic distribution, are consistent with most of them originating from a single assemblage of volcanic flow deposits, once continuous with volcanic flows to the south of the Memnonia Fossae source graben. These flows resurfaced the broad, north-south trending depression into which Mangala Vallis formed prior to any fluvial activity. Later flooding scoured and eroded this volcanic assemblage north of the Mangala source graben, resulting in the present distribution of the units within Mangala Vallis. Additionally, our observations suggest that a single period of catastrophic flooding, rather than multiple periods separated by tens to hundreds of millions of years, is consistent with and can plausibly explain the interior geology of Mangala Vallis. Further, we present a new scenario for the source and delivery of water to the Mangala source graben that models flow of groundwater through a subcryosphere aquifer and up a fracture that cracks the cryosphere and taps this aquifer. The results of our model indicate that the source graben, locally enlarged to a trough near the head region of Mangala, would have required less than several days to fill up prior to any spill-over of water to the north. Through estimates of the volume of material missing from Mangala (13,000-20,000 km 3 ), and calculation of mean discharge rates through the channel system (~5 · 10 6 m 3 s )1 ), we estimate that the total duration of fluvial activity through the Mangala Valles was 1-3 months. Notation:Parameter: Definition (Units); H:water head height in aquifer above base of cryosphere fracture (m); lateral length scale of aquifer (m); P atm : atmospheric pressure (500) (Pa);pressure at bottom of cryosphere fracture (Pa);pressure in unsaturated portion...

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Section: Model Backgroundmentioning

confidence: 98%

Mangala Valles, Mars: Assessment of Early Stages of Flooding and Downstream Flood Evolution

2005

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“…There are several problems with both of the models of Banerdt et al [1982] and Sleep and Phillips [1985]. Neither model accounts for the observed deviation from the predicted, purely radially oriented, compressional stress field, demonstrated in the analysis of the symmetry of the inferred compressive stresses (Figure 3).…”

Section: Models For the Origin Of The Stressesmentioning

confidence: 99%

Orientation, relative age, and extent of the Tharsis Plateau Ridge System

Watters¹,

Maxwell²

1986

J. Geophys. Res.

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The Tharsis ridge system is roughly circumferential to the regional topographic high of northern Syria Planum and the major Tharsis volcanoes. However, many of the ridges have orientations that deviate from the regional trends. Normals to vector means of ridge orientations, calculated in 10° boxes of latitude and longitude, show that the Tharsis ridges are not purely circumferential. Intersections of vector mean orientations plotted as great circles on a slereographic net show that the ridges are not concentric to a single point but to three broad zones. These data indicate either that the Tharsis ridge system did not form in response to a single regional compressional event with a single stress center or that the majority of the ridge system did form in a single event but with locally controlled deflections in the generally radially oriented stress field. Superposition relationships and relative ages suggest that the compressional stresses that produced the ridges occurred after the emplacement of the ridged plains volcanic units (early in the Hesperian period) but did not extend beyond the time of emplacement of the Syria Planum Formation units or the basal units of the Tharsis Montes Formation (during the latter half of the Hesperian period). Comparison of topographic data with the locations of ridges demonstrates a good correlation between the topographic edge of the Tharsis rise and outer extent of ridge occurrence. Compressional deformation related to Tharsis is present out to about 5100 km from the regional topographic center located near northern Syria Planum. The innermost extent cannot be determined because the ridged plains units have been buried by more recent volcanic units, although ridge formation appears to have extended farther inward than is presently observed. Models involving a combination of isoslatic stresses and stresses resulting from flexural loading appear to explain best the observed lensional features, topography, gravity, and. to a first approximation, the locations and orientations of the compressional ridges.

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“…As we commented in a previous section, none of the hypotheses pre sented up to here seems to solve the problem of the origin of this field. One additional problem of our tectonic model is that an important number of the measured faults would be strike slip ones, a type of fracture rarely detected on Mars (Carr 1974, Banerdt et al 1982, Golombek 1985, Watters and Golombek 1989, Ta naka et al 1991; but see also Forsythe andZimbebnan 1988, andSchultz 1989, for the only acknowledged examples).…”

Section: Planum Australe Tectonicsmentioning

confidence: 99%

Chasma Australe, Mars: Structural Framework for a Catastrophic Outflow Origin

Anguita

Babı́n

Benito

et al. 2000

Icarus

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Chasma Australe, 500 km long and up to 80 km wide, is the most remarkable of the martian south pole erosional reentrants carved in the polar layered deposits. We have interpreted Chasma Australe erosional and depositional features as evidence for a flood origin, which we have reconstructed using a modified Manning equation. We thus postulate that Chasma Australe originated in a catas trophic flood.The tectonic study of an area (roughly 20 million km2 in size)around Mars' south pole included the measurement and projection in rose diagrams of more than 300 lineaments, of which 85 were wrinkle ridges and the rest straight scarps. The whole set of linea ments can be explained by a stress field with a crI N100E in strike, the wrinkle ridges being reverse faults and the other lineaments di rect and strike-slip faults. The straight layout of parts of Chasma Australe almost 200 km long suggests that the chasm a was carved following a fracture network. The effectiveness of the erosional pro cess (the canyon is up to 1000 m deep) leads us to suspect that this carving was preceded by a sapping period. Endogenetic and exogenetic processes would thus have contributed to the origin of this landform.

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Thick shell tectonics on one‐plate planets: Applications to Mars

Cited by 121 publications

References 32 publications

Mangala Valles, Mars: Assessment of Early Stages of Flooding and Downstream Flood Evolution

Mangala Valles, Mars: Assessment of Early Stages of Flooding and Downstream Flood Evolution

Orientation, relative age, and extent of the Tharsis Plateau Ridge System

Chasma Australe, Mars: Structural Framework for a Catastrophic Outflow Origin

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