Geology and tectonics of Beta Regio, Guinevere Planitia, Sedna Planitia, and Western Eistla Regio, Venus: Results from Arecibo image data

Senske, D. A.; Campbell, D. B.; Stofan, E. R.; Fisher, P. C.; Head, J. W.; Stacy, N.J.S.; Aubele, J. C.; Hine, A. A.; Harmon, J. K.

doi:10.1007/bf00058901

Cited by 11 publications

(7 citation statements)

References 39 publications

(96 reference statements)

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“…Figure 3 is the fracture map, and Plate 1 is the regional geologic map. Many of the larger structures were visible in Arecibo radar and were described by Senske et al [1991].…”

Section: Mapping Proceduresmentioning

confidence: 95%

“…Eistla Regio is a discontinuous series of rises striking roughly E-W between longitudes 340øE and 55øE at latitudes 10-25øN. It was characterized before Magellan by its substantial gravity anomaly [Sjogren et al, 1983] and volcanic and rift structures [Senske et al, 1991] as a likely hot spot. Further work on Eistla Regio is also given by Senske et al…”

Section: Introductionmentioning

confidence: 99%

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Anatomy of a Venusian hot spot: Geology, gravity, and mantle dynamics of Eistla Regio

Grimm¹,

Phillips

1992

J. Geophys. Res.

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Eistla Regio is a series of broad swells, each up to a few thousand kilometers in diameter, in the equatorial highlands of Venus. It is characterized by strong positive free‐air gravity anomalies, shield volcanoes, and rift systems. We present a two‐part study of the western and central portions of this Venusian hot spot. First, Magellan radar images were mapped in order to understand the general geologic history of the region. Radial fracture systems both on the rises and volcanoes indicate uplift and associated faulting accompanied volcanic construction. Prominent fracture zones strike WNW to NW, parallel to the long axis of the highlands. The largest of these, Guor Linea, displays a progressive deformation history that may include minor clockwise rotation in addition to bulk NNE‐SSW extension. Other regional structural patterns also suggest this sense of rotation. The parts of Eistla studied here appear to be structurally distinct from surrounding regions, although volcanic radar‐bright plains and ridge‐and‐groove deformation to the west indicate an earlier, more diffuse thermal uplift. In the second part of our analysis, Pioneer Venus line‐of‐sight accelerations were inverted for vertical gravity which, when combined with topography, were used to solve for mass anomalies on the crust‐mantle boundary and in the upper levels of the mantle convective system. Both western and central Eistla appear to be sites of vigorous mantle upwelling. A linear upwelling appears beneath Guor Linea, indicating that rifting is actively driven by mantle flow. Minor crustal thinning may be present beneath western Eistla and the northern plains, whereas some thickening occurs beneath central Eistla and the southern plains. Heng‐O corona, in particular, may be the site of a small shallow mass anomaly of either compositional (thickened crust) or thermal origin. Mantle return flow is asymmetrically distributed about Eistla, being much stronger to the south than the north, and little flow is inferred at all to the NE in Bereghinya Planitia. These differences introduce a clockwise rotation to finite strain, in agreement with observations.

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“…Figure 3 is the fracture map, and Plate 1 is the regional geologic map. Many of the larger structures were visible in Arecibo radar and were described by Senske et al [1991].…”

Section: Mapping Proceduresmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Anatomy of a Venusian hot spot: Geology, gravity, and mantle dynamics of Eistla Regio

Grimm¹,

Phillips

1992

J. Geophys. Res.

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“…The study of volcanism on Venus has provided insight into several of these questions and issues. Previous analyses of Venera lander data [Surkov et al, 1984[Surkov et al, , 1987, Earth-based radar data [Campbell et al, 1984Senske et al, 1991a, b] and data from Venera 15/16 [Barsukov et al, 1986;Barsukov and Volkov, 1989; Barsukov et al, 1992] have shown the abundance of volcanic deposits on Venus and the diversity and association of some volcanic edifices and smactures. However, image resolution was poorer than 1-3 km, and coverage was regional, rather than global.…”

Section: Introductionmentioning

confidence: 99%

Venus volcanism: Classification of volcanic features and structures, associations, and global distribution from Magellan data

Head¹,

Crumpler²,

Aubele³

et al. 1992

J. Geophys. Res.

419

244

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A preliminary analysis of a global survey of Magellan data covering over 90% of the surface and designed to document the characteristics, location, and dimensions of all major volcanic features on Venus has revealed over 1660 landforms and deposits. These include over 550 shield fields (concentrations of small volcanoes <20 km in diameter), 274 intermediate volcanoes between 20 and 100 km diameter with a variety of morphologies, 156 large volcanoes in excess of 100 km diameter, 86 calderalike structures independent of those associated with shield volcanoes and typically 60–80 km in diameter, 175 coronae (annulus of concentric ridges or fractures), 259 arachnoids (inner concentric and outer radial network pattern of fractures and ridges), 50 novae (focused radial fractures forming stellate patterns), and 53 lava flood‐type flow fields and 50 sinuous lava channels (all of which are in excess of 102–103 km in length). The vast majority of landforms are consistent with basaltic compositions; possible exceptions include steep‐sided domes and festoons, which may represent more evolved compositions, and sinuous rules, which may represent more fluid, possibly ultramafic magma. The range of morphologies indicates that a spectrum of intrusive and extrusive processes have operated on Venus. Little evidence was found for extensive pyroclastic deposits or landforms, consistent with the inhibition of volatile exsolution and consequent disruption by the high surface atmospheric pressure. The large size of many volcanic features is evidence for the presence of very large magma reservoirs. The scale of resurfacing implied by individual features and deposits is typically much less than 125,000 km2. The areal distribution, abundance, and size distribution relationships of shield fields, arachnoids, novae, large volcanoes, and coronae strongly suggest that they are the surface manifestation of mantle plumes or hot spots and that the different morphologies represent variations in plume size and stage and thermal structure of the lithosphere. Maps of the global distribution of volcanic features show that they are broadly distributed globally, in contrast to the plate boundary concentrations typical of Earth. However, they are not randomly distributed on the surface of Venus. An observed deficiency of many volcanic features in several lowland areas of Venus may be due to an altitude‐dependent influence of atmospheric pressure on volatile exsolution and the production of neutral buoyancy zones sufficient to form magma reservoirs; this would favor lava floods and sinuous channels at low elevations and edifices and reservoir‐related features at higher elevations. A major concentration of volcanic features is observed in the Beta/Atla/Themis region, an area covering about 20% of the planet and centered on the equator. This region is unique in that it is the site of local concentrations of volcanic features with concentrations 2–4 times the global average, an interlocking network of rift and deformation zones, several broad rises several th...

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“…The plains of Navka and Guinevere (Figure 1) consist primarily of bright and mottled plains, a southern extension of mottled plains mapped in the equatorial region to about 40" N (Senske, 1990;Senske et al, 1991). The mottled plains contain evidence for multiple flow units, some of which are associated with large edifices such as Ushas Mons and others of which are probably related to individual volcanic domes and shields as previously observed in central Guinevere Planitia (Campbell et al, 1989).…”

Section: Navka-guinevere Planitiaementioning

confidence: 60%

“…The new high-resolution radar images have allowed us to classify and map features and units in that part of the planet and compare their distribution and possible modes of origin with features in other parts of Venus. These data are also used to examine the geology of the Venus southern hemisphere and make comparisons with the northern high latitudes observed by Veneras 15/16 (Barsukov et al, 1986) and the equatorial region (Campbell et al, 1989;Senske, 1990;Senske et al, 1991).…”

Section: Geologic Mapping: Methods Unit Description and Unit Charactmentioning

confidence: 99%

Geology and tectonics of the Themis Regio-Lavinia Planitia-Alpha Regio-Lada Terra area, Venus: Results from Arecibo image data

et al. 1991

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New radar images obtained from the Arecibo Observatory (resolution 1.5-4.0km) for portions of the southern hemisphere of Venus show that: the upland of Phoebe Regio contains the southern extension of Devana Chasma, a rift zone extending 4200 km south from Theia Mons and interpreted as a zone of extension; Alpha Regio, the only large region of tessera within the imaged area; is similar to tessera mapped elsewhere on the planet and covers a smaller percentage of the surface than that observed in the northern high latitudes; the upland made of Ushas, Innini and Hathor Montes consists of three distinct volcanic constructs; Themis Regio is mapped as an ovoid chain of radar-bright arcuate single and double ring structures, edifices and bright lineaments. This area is interpreted as a region of mantle upwelling and on the basis of apparent split and separated features, a zone of localized faulting and extension. Linear zones of deformation in Lavinia Planitia are characterized by lineament belts that are often locally elevated, are similar to ridge belts mapped in the northern high latitudes and are interpreted to be characterized mainly by compression; radar-bright lava complexes within Lavinia Planitia are unique to this part of the planet and are interpreted to represent areas of eruption of high volumes of extremely fluid lava; the upland of Lada Terra is bound to the north by a linear deformation zone interpreted as extensional, is characterized by large ovoids and coronae, is interpreted to be associated with an area of mantle upwelling, and is in contrast to the northern high latitude highland of Ishtar Terra. Regions of plains in the southern hemisphere cover about 78% of the mapped area and are interpreted to be volcanic in origin. Located within the area imaged (10-78" S) are 52 craters interpreted to be of impact origin ranging from 8 to 157 km in diameter. On the basis of an overall crater density of 0.94 craters/lo6 km', it is determined that the age of this part of the Venus surface is similar to the 0.3 to 1.0 billion year age calculated for the equatorial region and northern high latitudes. The geologic characteristics of the portion of the Venus southern hemisphere imaged by Arecibo are generally similar to those mapped elsewhere on the planet. This part of the planet is characterized by widespread volcanic plains, large volcanic edifices, and zones of linear belt deformation. The southern hemisphere of Venus differs from northern high latitudes in that tessera makes up only a small percentage of the surface area and the ovoid chain in Themis Regio is unique to this part of the planet. On the basis of the analysis presented here, the southern hemisphere of Venus is interpreted to be characterized by regions of mantle upwelling on a variety of scales (ovoids, region made up of Ushas, Innini and Hathor Montes), upwelling and extension (Themis Regio) and localized compression (lineament belts in Lavinia Planitia).

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Geology and tectonics of Beta Regio, Guinevere Planitia, Sedna Planitia, and Western Eistla Regio, Venus: Results from Arecibo image data

Abstract: New radar images (resolution 1.5-2.0 km) obtained from the Arecibo Observatory are used to assess the geology of a portion of the equatorial region of Venus (

Cited by 11 publications

References 39 publications

Anatomy of a Venusian hot spot: Geology, gravity, and mantle dynamics of Eistla Regio

Anatomy of a Venusian hot spot: Geology, gravity, and mantle dynamics of Eistla Regio

Venus volcanism: Classification of volcanic features and structures, associations, and global distribution from Magellan data

Geology and tectonics of the Themis Regio-Lavinia Planitia-Alpha Regio-Lada Terra area, Venus: Results from Arecibo image data

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