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Shields

Wrinkle ridges

Simple ridges

Lineaments

A B C A

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C

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MPR: 0 m

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High: 6449 m

Low: –1925 m

V–1 Topography

E

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point source

S–N Topographic Profile SE–NW Topographic Profile

pdd pla

pds pbs

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point source

pbd

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rb

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pdl pdl pla

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pbd pdl

psh

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psh1

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0 30 60 KILOMETERS

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ed

ed

psh

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psh1

pbd

80.9° N., 226.4° E. 80° N., 229.7° E. 80.6° N., 105.5° E. 87.3° N., 262.4° E. 75.6° N., 96.3° E.

1,2 3 4 5 6

0 20 40 KILOMETERS 0 20 40 KILOMETERS

0 20 40 KILOMETERS

0 20 40 KILOMETERS 0 20 40 KILOMETERS 0 20 40 KILOMETERS

78.1° N., 76.5° E. 76.8° N., 192.9° E. 75.5° N., 273.1° E. 75.9° N., 55.6° E. 76.2° N., 17.2° E.

7 8 9 10 11

0 20 40 KILOMETERS 0 20 40 KILOMETERS 0 20 40 KILOMETERS 0 20 40 KILOMETERS

0 20 40 KILOMETERS

81.2° N., 200.3° E. 85.4° N., 214.6° E. 82.5° N., 273.2° E. 81° N., 223.3° E. 86.8° N., 337.5° E.

12 13 14 15 16

0 20 40 KILOMETERS 0 20 40 KILOMETERS 0 20 40 KILOMETERS

0 20 40 KILOMETERS

78.4° N., 174.7° E. 84.6° N., 76.9° E. 84° N., 16.5° E. 75.2° N., 242.2° E. 78.2° N., 306.5° E.

17 18 19 20 21

0 20 40 KILOMETERS 0 20 40 KILOMETERS 0 40 80 KILOMETERS 0 40 KILOMETERS

0 20 40 KILOMETERS

81.2° N., 285.1° E. 78.2° N., 104.7° E.

22 23

0 40 80 KILOMETERS

0 20 40 KILOMETERS

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A. Heavily Deformed Units

B. Regional Plains Units

C. Local Plains Units

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0 30 60 KILOMETERS

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pds

pds

pdl

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pla

psh1

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pcbs

pdd

B

A

pds

pds

pdl

pdl

an

an

pla

plb

pcds

pcbs

pcbd pcbs

pcbs

ta

pdd

pdd

pdd

High : 4500 m

Low : –1000 m

3500 m

2500 m

1500 m

A1 A2 A3

0 20 40 KILOMETERS

High : 600 m

Low : –900 m

500 m

100 m

–200 m

–500 m

B1 B2

0 30 60 KILOMETERS

A1 A2 A3

0 20 40 KILOMETERS

High : 750 m

Low : –400 m

700 m

600 m

500 m

B1 B2

A1 A2 A3

0 40 80 KILOMETERS

High : 400 m

Low : –1400 m

Low : –100 m

0 m

–300 m

–650 m

–1000 m

High : 2700 m

Low : 0 m

2000 m

300 m

800 m

100 m

High : 670 m

Low : –20 m

650 m

350 m

50 m

1 2 3

0 60 120 KILOMETERS

High :1200 m

Low : –350 m

High :1200 m

Low : –500 m

900 m

400 m

–100 m

B3

0 40 80 KILOMETERS

High : 700 m

500 m

300 m

100 m

1000 m

300 m

–400 m

pbs

pbs

rb

pdl

pds

pds

pdd

pdd

pdd

pdl

rb

rb

pbd

pbd

pbd

pbd

pds

pds pdd

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psh1

rb

pdd

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pds

pds

pbs

pdl

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pdl

psh1

psh1

ta

psh1

pla

pds

pds

pds

pds

pdl

pdl

fb

fb

pcbs

pcbd

pdd

pdd

pdd

pdd

ta

ta

ta

ta

fb

fb

psh fb 1

psh1

pds

pdl pdl

psh1

psh1

pdd

pds

pdl

pdl

pdl

pdl

psh2

fb

fb

pbd

pbd

pbd

pds

ed

ed

ed

psh2

pla

pbd

pbd

pbd

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pbs

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an

an

rb

rb

pdl

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pds

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fb

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an

pds

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tb

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ta

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ta

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pbd

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rb

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rb

pdl pdl

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psh1

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ed

ed

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pcbd

wr lin

sr

pcbs

pcds

plb

plb

plb

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pla

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ssd

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c c

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fb

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ed

Printed on recycled paper

Any use of trade, product, or firm names in this publication is for descriptive purposes only 

and does not imply endorsement by the U.S. Government

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, 

Denver, CO 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3178

Suggested citation: Hurwitz, D.M., and Head, J.W., 2012, Geologic map of the Snegurochka 

Planitia quadrangle (V-1), Venus: U.S. Geological Survey Scientific Investigations Map 3178, 

scale 1:5,000,000 (http://pubs.usgs.gov/sim/3178/).

Geologic Map of the Snegurochka Planitia Quadrangle (V–1), Venus

By

Debra M. Hurwitz1 and James W. Head1

2012 1

Department of Geological Sciences, Brown University, Providence, RI

Scientific Investigations Map 3178

Atlas of Venus: Snegurochka Planitia Quadrangle (V–1)

Pamphlet accompanies map

Prepared for the

National Aeronautics and Space Administration

180°

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HEAVILY DEFORMED UNITS REGIONAL PLAINS UNITS LOCAL PLAINS UNITS STRUCTURES PREDOMINANT STRESS ENVIRONMENT

UNDIFFERENTIATED

CRATER

MATERIAL

TENSION

Units fb, pcds, pcbs, pla, plb, ed, psh2. Structure lin

TENSION

Units pdd, pbd, pcbd, psh, pds, pbs, fb. Structure lin

COMPRESSION

Unit rb. Structure wr

COMPRESSION

Units ta, tb, pdl, rb, an. Structures wr, sr, ssd

CORRELATION OF MAP UNITS

0 125 250 500 750 1,000

SCALE 1:1 004 000 (1 mm = 1.004 km ) AT 270° LONGITUDE

POLAR STEREOGRAPHIC PROJECTION

KILOMETERS

DESCRIPTION OF MAP UNITS

[Map units distinguished based on differences in morphology, texture, radar brightness, and stratigraphic 

relations. In general, units defined based on observations of emplaced material, but when deformation completely 

masks original material, the deformation characterizes the unit]

HEAVILY DEFORMED UNITS

Fracture belt unit—Tectonic units characterized by radar bright terrain and typically parallel 

fractures confined to belts of deformed material. Belts range from 10 – ~100 km in width and 

from ~200 km – >1200 km in length, with varied topographic signatures. Fractures associated 

with belts can be embayed by surrounding regional plains units or fractures can cut across plains 

units, suggesting formation over extended periods of time. Type areas: lat 78° N., long 79° E. 

Interpretation: Material of uncertain origin deformed into belts of parallel fractures as result of 

regional tensile stresses

Annulus unit—Radar bright units characterized by deformation in concentric lineations. Commonly 

embayed by adjacent regional and shield plains materials. Type areas: lat 78.4° N., long 271° E. 

Interpretation: Material deformed during early stages of corona development

Ridged belt unit—Radar bright units characterized by belts of single-orientation deformation ridges. 

Belts vary from 10 – >200 km in width and from 10 – >2000 km in length, with varied 

topographic signatures. Generally embayed by adjacent regional, shield, and lobate plains units. 

Type areas: lat 81° N., long 206° E. Interpretation: Material of uncertain origin deformed into 

belts of parallel ridges as the result of regional compressive stresses

Densely lineated plains material—Radar bright units characterized by significant deformation in 

only one orientation, typically expressed in parallel ridges and grooves typically spaced less than 

1 km apart. Commonly embayed by adjacent regional, shield, and lobate plains units and cut by 

fractures. Type areas: lat 79.8° N., long 250.7° E. Interpretation: Material deformed generally 

into ridges due to regional compressive stresses before subsequent embayment by regional 

volcanism

Tessera units—Radar bright material characterized by significant deformation of elevated precursor 

terrain. Consistently embayed or modified by surrounding units

Tessera, unit a—Deposits exhibiting deformation orientations in generally two orientations that 

intersect at high angles. Type areas: lat 81.7° N., long 97° E.

Tessera, unit b—Deposits having more subdued characteristic deformation pattern, though 

evidence of extensive deformation still evident in radar bright, heavily folded texture. Type area: 

lat 82.3° N., long 97.5° E. Interpretation: Old material of unknown origin substantially subjected 

to tectonic deformation before subsequent embayment by regional volcanic units

REGIONAL PLAINS UNITS

Bright smooth plains material—Deposits characterized by a higher radar backscatter than dark 

smooth plains unit, suggesting greater surface roughness. Unit can be deformed by wrinkle 

ridges and lineaments, indicating subsequent tectonic deformation. Generally the youngest 

regional plains unit. Type areas: lat 78° N., long 10° E. Interpretation: Young, thin volcanic 

flows of low viscosity possibly sourced from unresolved fissures or vents in regional plains units 

or associated with more local tectono-magmatic sources such as coronae

Dark smooth plains material—Smooth deposits distinguished by regions of uniformly low radar 

backscatter, possibly locally deformed by regional tectonic stresses that generated large wrinkle 

ridges in some locations and grabens traceable across plains units in other locations. Tectonic 

deformation does not obscure original radar dark unit, thus unit mapped as a dark smooth plains 

unit subjected to later tectonic activity. Materials generally embay all heavily deformed units as 

well as deformed plains and shield plains units, but dark smooth plains unit commonly superposed by bright smooth regional plains and lobate plains units. Type areas: lat 80° N., long 277° 

E. Interpretation: Young, thin volcanic flows of low viscosity

Bright deformed plains material—Rougher, brighter terrain than darker plains units at a 12.6 cm 

wavelength scale, with small-scale polygonal cracking or wrinkling of underlying terrain. Generally superposed on more heavily deformed deposits such as tessera, ridged belts, densely lineated 

plains units, as well as dark deformed plains unit, but bright deformed units commonly embayed 

by smoother plains, shield plains, and lobate plains units. Type areas: lat 82.3° N., long 178.6° 

E. Interpretation: Volcanic flows either jointed or deformed by subsequent localized tectonic 

stresses

Dark deformed plains material—Relatively smooth, radar dark deposits exhibiting evidence of 

subsequent deformation, generally in the form of polygonal cracking or localized, small-scale 

wrinkles in the terrain. Generally superposed on more heavily deformed units such as tessera, 

ridged belts, and densely lineated plains units, but dark deformed plains units generally embayed 

by smoother plains, shield plains, and lobate plains units. Type areas: lat 82° N., long 282.5° E. 

Interpretation: Volcanic flows either jointed or deformed by subsequent localized tectonic 

stresses

LOCAL PLAINS UNITS

Edifice material—Distinct features characterized by radar bright lines emanating from central 

topographic highs and by radial radar bright, hummocky material at great distances of up to 30 

km–50 km from the feature centers. Deposits both superpose and are embayed by lobate plains 

unit pla associated with Renpet Mons, suggesting synchronous emplacement. Type area: lat 

75.5° N., long 229.6° E. Interpretation: Local volcanism in flank eruptions of more viscous 

lavas, resulting in the formation of steep-sided volcanic domes; hummocky deposits on the 

flanks form from flank failure processes

Lobate plains units—Deposits characterized by distinctive lateral or radial textures and radar bright, 

digitate morphologies at outer extents of deposits. Lobate plains units are uniformly undeformed 

by wrinkle ridges and extensional lineaments, and typically represent the youngest unit, superposing adjacent regional plains units and deformed units, though a local shield plains unit psh2

superposes Renpet Mons. Textures of digitate and lobate morphologies associated with flows 

contained within mapped boundaries of pl units designated as flow fronts (lat 77° N., long 236.2° 

E.)

Lobate plains material a—Deposits radiating from central point sources. Type areas: lat 77° N., 

long 235° E.

Lobate plains material b—Deposits emanating from linear sources. Type areas: lat 79° N., long 

300° E. Interpretation: Lava flows associated with volcanic or tectono-magmatic sources such 

as large shield volcanoes, systems of shallow dikes, or coronae

Bright smooth corona plains material—Deposits characterized by higher radar backscatter than 

dark smooth corona plains unit pcds, suggesting that bright smooth corona plains unit has 

greater surface roughness. Unit pcbs generally the youngest plains deposits associated with 

coronae. Type areas: lat 80.8° N., long 292° E. Interpretation: Young volcanic flows of low 

viscosity associated with the latest stages corona formation

Dark smooth corona plains material—Smooth deposits distinguished by regions of uniformly low 

radar backscatter and insignificant tectonic deformation. Unit pcds generally spatially associated with coronae interior. Dark smooth corona plains units generally embay all heavily 

deformed units as well as deformed plains and shield plains units. Type areas: lat 77.7° N., long 

278° E. Interpretation: Relatively young volcanic flows of low viscosity associated with 

late-stage corona formation

Bright deformed coronae plains material—Bright deposits distinguished by small-scale polygonal 

cracking or wrinkling of underlying terrain, spatially associated with coronae. Deposits generally 

superpose unit an but are in turn embayed by bright smooth corona plains unit pcbs. Type areas: 

lat 80.5° N., long 289.3° E. Interpretation: Volcanic flows associated with earlier stages of 

coronae development; flows were either jointed or deformed by subsequent localized tectonic 

stresses and were then embayed by later volcanic activity

Shield plains units—Deposits characterized by clusters of small shield-like mounds (1–20 km in 

diameter) that generally have radar bright centers surrounded by more subdued radar bright 

aprons. Shield plains units are defined when aprons, interpreted to be volcanic flows associated 

with the mounds, overlap or lie in close proximity to other aprons (in other words, when the 

aprons cluster), forming radar-mottled appearances. Mounds may be randomly distributed in a 

cluster or aligned along a fracture

Lower shield plains material—Outcrops of the shield plains unit generally superposing heavily 

deformed units and deformed regional plains units but typically superposed by smooth regional 

plains units and lobate plains units. Type areas: lat 79° N., long 256.6° E.

Upper shield plains material—Outcrops of the shield plains unit embaying all surrounding units. 

Type areas: Atop Renpet Mons, lat 75.7° N, long 236.2° E., and at the north end of Szél-anya 

Lineae, lat 84° N., long 98° E. Interpretation: Clusters of small volcanoes fed from dikes propagating from a single, large subsurface magma source; aligned shields likely fed by laterally 

propagating dikes, and clustered shields likely fed by clusters of vertically ascending dikes

UNDIFFERENTIATED CRATER MATERIALS

Undifferentiated crater materials—Deposits generally characterized by radar bright material at 

least partially surrounding radar bright, deformed rings enclosing generally radar dark circles 

and in many cases central radar bright peaks. Type areas: lat 81° N., long 223.3° E. Interpretation: Craters of impact origin and associated ejecta deposits, crater rims, central peaks, and 

infilled material, either impact melt or flooded volcanic flows (or both)

EXPLANATION OF MAP SYMBOLS

Contact—Dashed where gradational; dotted where hidden

Shield

Wrinkle ridge (wr)

Simple ridge (sr)

Lineament (lin)

Channel

Crater rim, diameter <10 km

Crater rim, diameter >10 km

Caldera rim

Flow front

Crater central peak

Steep-sided dome (ssd)

Prepared on behalf of the Planetary Geology and Geophysics Program, 

Solar System Exploration Division, Office of Space Science, National 

Aeronautics and Space Administration

Edited by Theresa Iki

Cartography by Darlene A. Ryan

Manuscript approved for publication August 29, 2011

Descriptions of nomenclature used on map are listed at 

http://planetarynames.wr.usgs.gov/

Figure 2. Magellan altimetry data with 10–30 km horizontal resolution and 80–100 m vertical resolution. 

The data indicate that the lowest terrain in V–1 is 1925 km below mean planetary radius (MPR, 6051.8 km) 

and that the highest terrain in V–1 is 6449 km above MPR.

Figure 4. A representation of identified structures within Snegurochka Planitia, V–1, including lineaments, 

wrinkle ridges, simple ridges, and small shield volcanoes. A, The two locations of high concentrations of 

lineaments are observed near the northern extent of Szél-anya Lineae (lat 83° N., long 98° E.) and on Snegurochka Planitia near Pomona Corona (lat 78° N.–83° N., long 286° E.–320° E.); B, Wrinkle ridges are 

concentrated in Louhi Planitia near Lukelong Dorsa and Klenova crater (lat 75° N.–82° N., long 82° E.–178° 

E.). Other less dense clusters of wrinkle ridges are observed to deform Snegurochka Planitia near Anahit 

Corona (lat 80° N., long 270° E.). These areas of densely clustered wrinkle ridges and lineaments generally 

deform the smoother plains units. In contrast, simple ridges are concentrated in the more heavily deformed 

units associated with Dennitsa Dorsa, Fulgora Dorsa, Lukelong Dorsa, the coronae, and the northern 

boundary of Itzpapalotl Tessera. C, Small shields generally cluster near boundaries at intermediate elevations 

between more heavily deformed terrains such as densely lineated plains and regional plains units. These 

features are generally observed to be partially embayed by smoother plains units, though two locations of 

small shields, one on the summit of Renpet Mons (lat 76° N., long 236° E.) and one near the northernmost 

extent of Szél-anya Lineae (lat 83° N., long 98° E.), appear to cover surrounding units.

Figure 5. Asymmetric lobate plains associated with Sarasvati Mons and Heloha Fluctus near the boundary 

between Snegurochka Planitia and Itzpapalotl Tessera (lat 75° N.–78° N., long 356° E.–336° E.). The southeast 

portion of the lobate plains unit (pla) lies on the slope of the topographic boundary (topographic profile 

SE–NW), and the deposits extend for more than 170 km to the northwest in Heloha Fluctus, locally covering 

surrounding plains materials. The asymmetry of unit pla is due to the slope in the local topography as can be 

seen in topographic profile S–N (circles denote the location of the volcano center). The slope associated with 

the topographic boundary forces the deposits to accumulate at the base of the slope, and the gradual northwest 

slope of the low-lying plains focuses the deposits down slope in the asymmetrical trend observed. Flow margins 

with digitate morphologies contained within unit pla are mapped as flow fronts (arrows).

Figure 6. Impact craters found in Snegurochka Planitia, V–1. White arrows in the 

upper right corner of each panel indicate north. Twenty-three craters were found 

(see table 1), ranging in diameter from 2.9 km (unnamed crater, 1: lat 80.9° N., long 

226.5° E.) to 143.5 km (Klenova crater, 23: lat 78.2° N., long 104.7° E.). Crater 

morphologies vary from a small, multi-crater morphology (3) and the most 

common flat-bottomed, radar dark-filled crater with a central peak (for example, 9) 

to one of the largest multi-ring basins found on Venus (Klenova crater). 

Embayment relations also vary, with some craters partially covered by surrounding 

material (for example, 22) while others deposit ejecta (for example, 10) and, in the 

case of Volkova crater (20), impact melt over surrounding materials. The craters 

observed in V–1 lack obvious clustering, a trend that is consistent with the nearly 

random distribution of craters observed globally on Venus.

Figure 8. Spatial distributions of unit classes identified within V–1, 

including A, heavily deformed units; B, regional plains units; and C, 

local plains units.

Figure 3. A, Venera 15/16 data fill in gaps in Magellan data; B, Geologic map based on observations made 

using Venera 15/16 data (Venus Venera 15/16 atlas, Kotelnikov and others, 1989); C, Geologic map based 

on observations made using Magellan data. The two interpretations of significant features within V–1 are 

similar, though several differences can be identified between the two interpretations. For example, Szél-anya 

Lineae was identified as a distinct geologic unit from the ridged belt of Dennitsa Dorsa using Magellan data 

while it was identified as the same geologic unit using Venera data. Also, additional lobate plains units and 

regional plains subunits were identified using Magellan data. These differences in interpretation can be 

attributed to a significant increase in resolution of Magellan data relative to Venera data.

Figure 14. Examples of the stratigraphy of small shield volcanoes 

observed in V–1: panel 1 displays the Magellan radar image of the 

features, and panel 2 displays the map of interpreted unit relations. A, 

The lower shield plains unit (psh1) in this area (lat 83° N., long 290° 

E.) appear clustered between the boundaries of densely lineated plains 

(unit pdl) deposits and regional plains units (pds, pdd, pbs, pbd). 

Shields are generally not deformed by structures associated with unit 

pdl deposits indicating that they formed later, and shields that are 

located within the regional plains units appear smaller and less 

distinctive than those within unit pdl materials, indicating that they 

have been partially embayed by younger plains units. This stratigraphic sequence is consistent with the trends identified elsewhere on 

Venus. B, Similarly, the lower shield plains unit (psh1) shown in this 

area (lat 77° N., long 180° E.) are found clustered on outcrops of unit 

pdl but are covered by the adjacent smooth plains units pds. These 

shields appear to be aligned with lineaments interpreted to be grabens 

that deform the outcrops of unit pdl, suggesting that shallow laterally 

propagating dikes are feeding local surface eruptions. C, In contrast, 

the upper shield plains unit psh2 located near the crest of the young, 

large shield volcano Renpet Mons (lat 76° N., long 240° E.) clearly 

embay the central caldera, indicating that these small shields are the 

youngest feature in this area.

Figure 16. Stratigraphic relations of tessera: panel 1 shows the 

Magellan SAR (125 m/pix) images; panel 2 shows the interpreted maps; 

and panel 3 shows the topography of the areas where available. A, 

Spatial relations between tessera subunits ta and tb and surrounding 

radar bright smooth (unit pbs) and radar dark deformed plains (unit 

pdd) units in a region centered at lat 82° N., long 99° E. The plains units 

embay the tessera unit, indicating that the tessera unit is older than the 

surrounding plains units. B, Spatial relations between tessera unit ta, 

densely lineated plains materials (unit pdl), and radar dark smooth 

regional plains materials (unit pds) near lat 76° N., long 339° E. In this 

case structures associated with the unit ta appear to deform unit pdl, 

suggesting that some unit pdl may predate or coincide with unit ta.

Figure 20. Stratigraphic relations of regional plains units pdd, pbd, 

pds, and pbs: panel 1 shows Magellan SAR images; panel 2 shows the 

interpreted maps; and panel 3 shows the topography of the areas where 

available. A, Spatial relations between the boundary of the ridged belt 

Dennitsa Dorsa (unit rb) with radar dark smooth and deformed regional 

plains units (pds, pdd) within Louhi Planitia near lat 83° N., long 184° 

E. The generally low-lying unit pds embays the unit rb as well as unit 

pdd and is subsequently left relatively undeformed. If the topographic 

signature is correct, a ridge along the margin of the unit rb may have 

formed a barrier to the flow of regional plains units, keeping the 

low-lying portion of the belt from being flooded. B, Spatial relations 

between bright smooth regional plains unit pds and dark deformed and 

smooth regional plains units (pdd, pds) bordering densely lineated 

plains (unit pdl) associated with the northern boundary of Fortuna 

Tessera near lat 78° N., long 5° E. Unit pdl is significantly higher in 

elevation than the surrounding plains units (see fig. 2), and unit pds

appears to have embayed unit pdl up to the topographic boundary. 

These plains units were subsequently subjected to deformation, leading 

to the formation of wrinkle ridges, after which unit pbs was emplaced, 

partially covering unit pds. These bright plains materials tend to be 

relatively thin, allowing the underlying dark plains unit and wrinkle 

ridges to remain somewhat visible.

Figure 17. Stratigraphic relations of densely lineated plains unit pdl: 

panel 1 shows a Magellan SAR image; panel 2 shows the interpreted 

map of the area; and panel 3 shows the topography of the area. This 

figure shows the spatial relations between units pdl, psh1, pdd, pbd, 

and pds near lat 79° N., long 252° E. Outcrops of unit pdl in this area 

appear to be embayed by neighboring outcrops of unit psh1 which are 

in turn embayed by low elevation regional plains units (pdd, pbd, pds). 

These embayment relations suggest that unit pdl formed first, followed 

by emplacement of first unit psh1 and then the emplacement of regional 

plains units.

Figure 23. Stratigraphic relations of lobate plains (unit pla): panel 1

shows a Magellan SAR image, panel 2 shows the interpreted map, and 

panel 3 shows topography of the area. This image shows spatial 

relations between unit pla associated with the large shield volcano 

Renpet Mons, edifices (unit ed), and the upper unit of shield plains (unit 

psh2) near lat 77° N., long 79° E. Unit pla appears to originate from the 

caldera feature at the peak of Renpet Mons and to flow down the flanks 

of the volcano to form the characteristic radial and digitate morphology 

associated with the unit. Margins of digitate morphology contained 

within unit pla are mapped as flow fronts (arrows). The steeper, radar 

bright unit ed formed on the flanks of Renpet Mons after some centrally 

derived flows were emplaced, but unit ed has since deflected subsequent flows, indicating that these different volcanic features likely 

formed somewhat concurrently. The caldera of Renpet Mons has since 

been embayed by later emplacement of unit psh2, indicating that these 

shields represent the most recent volcanism in this area.

Figure 18. Stratigraphic relations of fractures associated with Anahit 

Corona (left of image) and Pomona Corona (lower right of image): 

panel 1 shows a Magellan SAR image of the region; panel 2 shows the 

interpreted map; and panel 3 shows the topography of the area. Early 

activity associated with the coronae includes the formation of the annuli 

(unit an) and deformed units (ta, pdl), the emplacement of local radar 

bright coronae units that were subsequently deformed (unit pcbd), and 

the formation of lineaments that cut across adjacent units. These units 

and structures have been embayed and truncated by subsequent regional 

plains emplacement (unit pds) which in turn were subsequently 

deformed by wrinkle ridge formation (arrows A). The most recent 

activity is observed in deposits of smooth coronae flows both inside 

(unit pcds) and outside (unit pcbs) the coronae and in grabens that cut 

the regional plains units (arrow B). These grabens appear to be 

associated with Pomona Corona and fed local eruptions of lobate plains 

materials (pdl) located between Anahit Corona and Pomona Corona.

Figure 22. Stratigraphic relations of fracture belts (unit fb): panel 1 

shows Magellan SAR images; panel 2 shows the interpreted maps; and 

panel 3 shows topography of the areas where available. A, Spatial 

relations between the fracture belt Szél-anya Lineae (unit fb), tessera 

(unit ta), regional plains units (pdd, pbd, pds, pbs), and corona plains 

units (pcbs, pcbd) near lat 77° N., long 79° E. In contrast to the 

portion of Szél-anya Lineae shown in B, this portion of unit fb appears 

to have been embayed by the surrounding low-lying regional plains 

units (pdd, pbd, pds). A low-lying region of unit fb may have been 

protected from embayment by ridges along the margins of the belt. The 

variation in embayment relations along the fracture belt may indicate 

that while portions of the fracture belt became inactive over time, other 

portions may have increased in activity, extending the fracture belt 

across the region (fig. 21B). B, Spatial relations between both an 

unnamed fracture belt (unit fb) and lobate plains (unit pla) associated 

with the large shield volcano Laka Mons, and surrounding regional 

plains units (pds, pbd) near lat 83° N., long 98.6° E. Like the fracture 

belt shown in B, this fracture belt appears to have deformed units pdl

and pds before being embayed by subsequent emplacement of unit pla

that covers both unit fb and the surrounding plains units (pdl, psh1, 

pds, pcbs, pcbd), indicating that volcanism represents the most recent 

activity in this area. Lobate plains (unit pla) associated with Laka 

Mons appear to thin with distance from the source and associated 

fracture belt, as wrinkle ridges do not appear beneath the flows near the 

fracture belt but do appear from beneath the apparently thinner flows 

farther into the plains.

No topography available

No topography available

Figure 21. Stratigraphic relations of individual shield volcanoes and 

shield plains units psh1 and psh2: panel 1 shows Magellan SAR 

images; panel 2 shows the interpreted maps; and panel 3 shows 

topography of the areas where available. A, Spatial relations between 

the lower shield plains unit (psh1), densely lineated plains material 

(pdl), and radar dark smooth and deformed plains units (pds, pdl) near 

lat 77° N., long 79° E. The shields within unit psh1 are characterized by 

overlapping radar bright aprons that appear to cover the unit pdd and 

unit pdl. All of these units (psh1, pdd, and pdl) have subsequently been 

embayed by typically lower lying unit pds that has not since been 

subjected to local tectonic deformation, suggesting that the shields in 

the more heavily deformed units (pdd and pdl) are relatively old. A, 

Spatial relations between the upper shield plains unit (psh2), the 

fracture belt Szél-anya Lineae (unit fb), and radar bright deformed 

plains (unit pbd) near lat 83° N., long 99° E. In this area unit pbd

appears to be the first unit to be emplaced after nearby unit ta. The 

fractures associated with Szél-anya Lineae clearly cut through these 

deposits of pbd, suggesting relatively recent extensional activity in this 

vicinity. The outcrops of unit psh2 located in the center of this portion 

of unit fb feed flows that cover the parallel grabens and remain 

relatively undeformed, indicating that they are the youngest features in 

this area.

No topography available

Figure 19. Stratigraphic relations of the ridged belt unit rb: panel 1 

shows Magellan SAR images; panel 2 shows the interpreted maps; and 

panel 3 shows the topography of the areas where available. A, Spatial 

relations between the ridged belt Dennitsa Dorsa (unit rb), densely 

lineated plains material (pdl), and radar bright and dark deformed 

regional plains units (pbd, pdd) near lat 85° N., long 71° E. In this 

case, the structures associated with unit rb appear to be deforming the 

unit pdl, altering the orientation of the lineaments within the densely 

lineated plains unit to curve in line with the ridged belt. The 

surrounding plains units appear to embay low-lying areas and cover 

some deformation associated with the tectonic units, but they have also 

been subsequently deformed in a manner similar to the original tectonic 

units, possibly indicating long-term tectonic activity in this area. See 

figure 10A (in pamphlet) for a topographic profile of Dennitsa Dorsa. B, 

Spatial relations between the ridged belt Lukelong Dorsa (unit rb) and 

surrounding units pdl, pbs, and pds near lat 77° N., long 160° E. 

Lukelong Dorsa may also have been embayed by regional plains units, 

though wrinkle ridges that run parallel to this ridged belt and extensional lineaments that run perpendicular to this ridged belt may indicate 

extended compression (in the orientation of the arrows) and possibly 

ongoing ridged belt formation in this area. See figure 10B (in pamphlet) 

for a topographic profile of Lukelong Dorsa.

No topography available

Sarasvati

Mons

Saga Vallis

Vires-Akka Chasma

Itzpapalotl

Tessera

Fortuna Tessera

Fulgora

Dorsa

Uorsar Rupes

Heloha Fluctus

Dashkova

Misne Chasma

SNEGUROCHKA

PLANITIA

LOUHI

PLANITIA

Valborg

Lagerlöf

Hua Mulan

Landowska

Janice

Tatyana

Sveta

Laka

Mons

Olokun Vallis

Pomona

Corona

Anahit Corona

Tursunoy

Efimova

Odilia

Rudneva

Volkova

Tünde

Renpet

Mons

Eirene

Tholus

Yansa

Tholus

Akka

Tholus

Maslenitsa

Corona

Molpe

Colles

Dickinson

Lukelong Dorsa

Dennitsa Dorsa

Klenova

Radka

Gina

Eugenia

Ulrique

Ruslanova

Tezan Lineae

Oddibjord Tessera

Szél-anya Lineae

Fernandez

Semuni Dorsa

U.S. Department of the Interior

U.S. Geological Survey