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VOLCANIC EDIFICE AND FLOW MATERIAL CORONA FLOW MATERIAL

SEQUENCE OF MAP UNITS IMPACT

CRATER

PLAINS MATERIAL MATERIAL

DESCRIPTION OF MAP UNITS

[Subunits (members) in the map area associated with a specific source are numbered, if stratigraphic 

relations between them could be determined (for example, units fSe1 and fSe2), or lettered, if not 

all members are in contact and, therefore, age relations are ambiguous (for example, units fTya, 

fTyb, fTyc, fTyd)]

VOLCANIC EDIFICE AND FLOW MATERIAL

Material typically of limited extent from identifiable source

Rohina Tholus flow material—Intermediate- to high-backscatter, digitate deposits 

extending from Rohina Tholus, which sits upon Ukemochi Corona. Type area: lat 

39° S., long 294° E. Interpretation: Lava flows from central or flank vents of the 

Rohina Tholus edifice

Kwannon Tholus flow material—Intermediate-backscatter, sheet-like deposits occurring on the flanks of the Kwannon Tholus edifice. Type area: lat 26.4° S., long 297° 

E. Interpretation: Lava flows from central or flank vents of the Kwannon Tholus 

edifice

Justitia Tholus flow material—Lobate to sheet-like deposits with low to intermediate 

backscatter located on the Justitia Tholus edifice. Type area: lat 28° S., long 296.5° 

E. Interpretation: Lava flows from central or flank vents of the Justitia Tholus 

edifice

Mertseger Mons flow material—Low- to intermediate-backscatter, digitate to sheetlike deposits occurring on the summit and flanks of the Mertseger Mons edifice. 

Type area: lat 38° S., long 271° E. Interpretation: Lava flows from central or flank 

vents of the Mertseger Mons edifice

Tefnut Mons flow material—Intermediate- to low-backscatter, sheet-like deposits 

occurring on the flanks of the Tefnut Mons edifice. Type area: lat 38° S., long 300° 

E. Interpretation: Lava flows from central or flank vents of the Tefnut Mons edifice

Angerona Tholus flow material—Variable backscatter deposits occurring on the flanks 

of the Angerona Tholus edifice. Type area: lat 30° S., long 287° E. Interpretation: 

Lava flows from central or flank vents of the Angerona Tholus edifice

Chloris Mons flow material

Member 2—Digitate to sheet-like, variable backscatter deposits on the summit and 

flanks of the Chloris Mons edifice. Type area: lat 46° S., long 294° E. Interpretation: Lava flows from central or flank vents of the Chloris Mons edifice

Member 1—Low- to intermediate-backscatter, sheet-like deposits occurring on the 

flanks of the Chloris Mons edifice. Type area: lat 44° S., long 296.5° E. Interpretation: Lava flows from central or flank vents of the Chloris Mons edifice

Abeona Mons flow material—Variable backscatter, lobate to sheet-like deposits occurring on the summit and flanks of the Abeona Mons edifice. Type area: lat 45° S., 

long 273° E. Interpretation: Lava flows from central or flank vents of the Abeona 

Mons edifice

Mielikki Mons flow material

Member 2—Digitate to sheet-like, variable backscatter deposits occurring on the 

summit and flanks of the Mielikki Mons edifice. Type area: lat 28° S., long 282° E. 

Interpretation: Lava flows from central or flank vents of the Mielikki Mons edifice

Member 1—Sheet-like, low-backscatter deposits occurring on the flanks of the 

Mielikki Mons edifice. Type area: lat 26° S., long 285° E. Interpretation: Lava 

flows from central or flank vents of the Mielikki Mons edifice

Siduri Mons flow material—Sheet-like deposits occurring on the Siduri Mons edifice. 

Type area: lat 42.8° S., long 297° E. Interpretation: Lava flows from central or 

flank vents of the Siduri Mons edifice

Ts’an Nu Mons flow material—Intermediate-backscatter, digitate to sheet-like deposits occurring on the summit and flanks of the Ts’an Nu Mons edifice. Type area: lat 

27.5° S., long 273° E. Interpretation: Lava flows from central or flank vents of the 

Ts’an Nu Mons edifice

Volcanic center flow material—Flow material having radar-dark to radar-bright 

backscatter coefficients and lobate boundaries. Multiple occurrences in map area 

with varying superposition relations. Type area: lat 43° S., long 293.5° E. Interpretation: Lava flows from central or flank vents of an unnamed volcanic complex

Edifice field flow material—Numerous small shields and cones surrounded by lobate 

deposits with moderate backscatter. Multiple occurrences in map area with varying 

superposition relations. Type area: lat 33° S., long 283° E. Interpretation: Fields of 

small volcanic edifice and associated flows of varying ages 

CORONA FLOW MATERIAL

Material related to coronae, typically of limited extent and varying from deformed materials to 

digitate or sheet-like deposits

Lilwani Corona flow material—Intermediate-backscatter materials with lobate boundaries in the interior of Lilwani Corona. Flows superpose rift faults. Type area: lat 

30° S., long 272° E. Interpretation: Lava flows from vents in the interior of Lilwani 

Corona

Xmukane Corona flow material—Digitate to sheet-like, variable backscatter flow 

material extending in a fan from the rim and interior of Xmukane Corona. Type 

area: lat 28° S., long 270.5° E. Interpretation: Lava flows from vents on the rim 

and the interior of Xmukane Corona

Shulamite Corona flow material—Intermediate- to high-backscatter, digitate to 

sheet-like flow material extending from the rim and interior of Shulamite Corona. 

Flows deformed by and cover rift faults. Type area: lat 36° S., long 283° E. Interpretation: Lava flows from vents in the interior, rim, and flanks of Shulamite 

Corona

Gertjon Corona flow material

Member 2—Sheet-like, low-backscatter flow material in the interior of Gertjon 

Corona. Type area: lat 30° S., long 276° E. Interpretation: Lava flows from vents 

in the interior of Gertjon Corona

Member 1—Digitate, low- to intermediate-backscatter material extending from the 

rim and interior of Gertjon Corona. Type area: lat 30° S., long 277.5° E. Interpretation: Lava flows from vents on the rim and the interior of Gertjon Corona

Shiwanokia Corona flow material

Member 2—Intermediate- to high-backscatter, digitate to sheet-like flow material 

extending from the rim and interior of Shiwanokia Corona. Type area: lat 44.5° S., 

long 280° E. Interpretation: Lava flows from vents of Shiwanokia Corona

Member 1—Sheet-like, low- to intermediate-backscatter flow material extending 

from the rim and interior of Shiwanokia Corona. Flows deformed by and cover rift 

faults. Type area: lat 39.5° S., long 276° E. Interpretation: Lava flows from vents 

of Shiwanokia Corona

Obiemi Corona flow material

Member 3—Digitate, variable backscatter flow material extending in a fan from the 

flank of Obiemi Corona. Type area: lat 32° S., long 274° E. Interpretation: Lava 

flows from a vent on the flank of Obiemi Corona

Member 2—Low- to intermediate-backscatter, digitate to sheet-like, variable 

backscatter flow material extending from the interior of Obiemi Corona. Type area: 

lat 32° S., long 276° E. Interpretation: Lava flows from vents in the interior of 

Obiemi Corona

Member 1—Digitate, intermediate-backscatter flow material from the rim and 

interior of Obiemi Corona. Deformed by rift faults and rim of Obiemi. Type area: 

lat 34° S., long 274° E. Interpretation: Lava flows from vents of Obiemi Corona

Zywie Corona flow material—Variable backscatter, sheet-like flow material extending 

from the rim and interior of Zywie Corona. Type area: lat 38° S., long 291° E. 

Interpretation: Lava flows from vents of Zywie Corona

Ama Corona flow material—Low- to intermediate-backscatter, sheet-like flow material with lobate boundaries extending from the rim and interior of Ama Corona. 

Type area: lat 46.5° S., long 276° E. Interpretation: Lava flows from vents of Ama 

Corona

Orbona Corona flow material—Intermediate- to high-backscatter, digitate to sheetlike flow material associated with Orbona Corona. Type area: lat 47.5° S., long 

292° E. Interpretation: Lava flows from vents of Orbona Corona

Tamiyo Corona flow material

Member d—Low-backscatter, sheet-like flow material in the interior of Tamiyo 

Corona. Deformed by rift faults. Type area: lat 35.5° S., long 299° E. Interpretation: Lava flows from vents in the interior of Tamiyo Corona

Member c—Fan-shaped, digitate, intermediate-backscatter flow material extending 

from the rim of Tamiyo Corona. Type area: lat 34° S., long 297.5° E. Interpretation: Lava flows from vents near the rim of Tamiyo Corona.

Member b—Variable backscatter, digitate to sheet-like flow material extending from 

the rim of Tamiyo Corona. Type area: lat 34° S., long 299° E. Interpretation: Lava 

flows from vents of Tamiyo Corona

Member a—Intermediate- to high-backscatter, sheet-like flow material extending 

from the rim and interior of Tamiyo Corona. Deformed by corona rim and by rift 

faults. Type area: lat 36° S., long 298.3° E. Interpretation: Lava flows from vents 

of Tamiyo Corona

Bibi-Patma Corona flow material

Member 3—Sheet-like flow material with variable backscatter extending from BibiPatma Corona. Type area: lat 49.5° S., long 299° E. Interpretation: Lava flows 

from vents of Bibi-Patma Corona

Member 2—Intermediate-backscatter, sheet-like flow material extending from BibiPatma Corona. Type area: lat 47.5° S., long 299° E. Interpretation: Lava flows 

from vents of Bibi-Patma Corona

Member 1—Sheet-like flow material with low backscatter extending from BibiPatma Corona. Type area: lat 44.5° S., long 299.5° E. Interpretation: Lava flows 

from vents of Bibi-Patma Corona

Ukemochi Corona flow material

Member e—Digitate, intermediate-backscatter flows extending from the rim of 

Ukemochi Corona. Type area: lat 41.5° S. long 297.5° E. Interpretation: Lava 

flows from vents on the rim of Ukemochi Corona

Member d—Low-backscatter, sheet-like flow material in the interior of Ukemochi 

Corona. Type area: lat 38.5° S., long 297.5° E. Interpretation: Lava flows from 

vents in the interior of Ukemochi Corona

Member c—Intermediate- to high-backscatter, digitate to sheet-like flow material 

extending from the rim and interior of Ukemochi Corona. Deformed by rift faults. 

Type area: lat 38° S., long 298°. Interpretation: Lava flows from vents of Ukemochi Corona

Member b—Low- to intermediate-backscatter, sheet-like flow material in the interior 

of Ukemochi Corona. Type area: lat 38° S., long 297° E. Interpretation: Lava flows 

from vents in the interior of Ukemochi Corona

Member a—Intermediate- to high-backscatter material in the interior and rim of 

Ukemochi Corona. Deformed by corona rim and rift faults. Type area: lat 42° S., 

long 297° E. Interpretation: Deformed lava flows from vents of Ukemochi Corona

Durga Corona flow material—Intermediate-backscatter, sheet-like flow material 

extending from the interior of Durga Corona. Flows deformed by rift faults. Type 

area: lat 27.5° S., long 287° E. Interpretation: Lava flows from vents of Durga 

Corona

Rigatona Corona flow material—Sheet-like, low- to intermediate-backscatter flow 

material extending from the rim and interior of Rigatona Corona. Flows deformed 

by rift faults. Type area: lat 32° S., long 280° E. Interpretation: Lava flows from 

vents of Rigatona Corona 

Nzambi Corona flow material

Member 2—Variable backscatter, digitate to sheet-like flow material extending from 

the rim of Nzambi Corona. Type area: lat 46° S., long 287.5° E. Interpretation: 

Lava flows from vents of Nzambi Corona

Member 1—Low- to intermediate-backscatter, sheet-like material in interior of 

Nzambi Corona. Type area: lat 45° S., long 286° E. Interpretation: Lava flows 

from vents in the interior of Nzambi Corona

Latta Corona flow material—Intermediate-backscatter, sheet-like flow material 

extending from the rim and interior of Latta Corona. Flows deformed by rift faults. 

Type area: lat 38° S., long 287° E. Interpretation: Lava flows from vents of Latta 

Corona

Semiramus Corona flow material

Member 2—Intermediate- to high-backscatter, digitate to sheet-like flow material 

extending from the rim and interior of Semiramus Corona. Flows deformed by 

corona rim fractures and rift faults. Type area: lat 36° S., long 294° E. Interpretation: Lava flows from vents of Semiramus Corona

Member 1—Sheet-like, intermediate-backscatter flow material extending from 

Semiramus Corona. Flows deformed by rift faults. Type area: lat 34.9° S., long 

296.8° E. Interpretation: Lava flows from vents of Semiramus Corona

Anjea Corona flow material—Intermediate- to high-backscatter, digitate to sheet-like 

flow material associated with Anjea Corona. Type area: lat 30° S., long 282.5° E. 

Interpretation: Lava flows from vents of Anjea Corona

Santa Corona flow material

Member 2—Intermediate-backscatter, digitate flow material extending from the rim 

and interior of Santa Corona. Type area: lat 33° S., long 291° E. Interpretation: 

Lava flows from vents of Santa Corona

Member 1—Intermediate- to high-backscatter, digitate to sheet-like flow material 

extending from Santa Corona. Flows deformed by rift faults. Type area: lat 34° S., 

long 288° E. Interpretation: Lava flows from vents of Santa Corona

Erigone Corona flow material—Sheet-like, low- to intermediate-backscatter flow 

material extending from the interior of Erigone Corona. Flows deformed by rift 

faults. Type area: lat 34° S., long 283° E. Interpretation: Lava flows from vents of 

Erigone Corona

Tacoma Corona flow material—Intermediate-backscatter, sheet-like flow material 

extending from the interior of Tacoma Corona. Flows deformed by rift faults. Type 

area: lat 37° S., long 288° E. Interpretation: Lava flows from vents of Tacoma 

Corona

Navolga Corona flow material—Sheet-like, low- to intermediate-backscatter flow 

material extending from the rim and interior of Navolga Corona. Flows deformed 

by faults. Type area: lat 48.3° S., long 295.5° E. Interpretation: Lava flows from 

vents of Navolga Corona

Ikas Coronae flow material—Sheet-like, low- to intermediate-backscatter flow material extending from the rim and interior of Ikas Coronae. Flows deformed by faults. 

Type area: lat 40° S., long 288° E. Interpretation: Lava flows from vents of Ikas 

Coronae

PLAINS MATERIAL

Typically covers large areas and ranges from dark to moderate-backscatter cross section

Smooth plains material—Relatively radar dark, areally limited deposits, frequently 

characterized by indistinct small edifices and pits. Very low abundance of fractures 

or wrinkle ridges. Type area: lat 26.5° S., long 296.5° E. Interpretation: Volcanic 

plains composed of indistinct flow units emanating from pits and small edifices 

Themis Regio lobate plains material—Limited, generally level deposits with lobate 

margins on the Themis Regio rise with relatively uniform backscatter over 

hundreds of kilometers; minor occurrences of domes, cones, shields, fractures, and 

ridges. Type area: lat 31° S., long 289° E. Interpretation: Volcanic plains composed 

primarily of flow units formed throughout the history of the formation of Themis 

Regio. May have emanated from coronae or fractures associated with rifting

Helen Planitia composite plains material—Low- to intermediate-backscatter, mottled 

deposits covering large region, with wrinkle ridges, fractures, and patchy flow 

deposits. Type area: lat 49° S., long 285° E. Interpretation: Volcanic plains 

composed of indistinct flow units emanating unknown sources.

Mottled plains material—Extensive, generally level deposits with variable backscatter 

characterized by multiple patch volcanoes, areas of fracturing, wrinkle ridges, 

domes, cones, and shields. Type area: lat 32° S., long 295° E. Interpretation: Volcanic plains built up of a number of interfingered deposits, with minor extension and 

compression occurring locally

Themis Regio fractured plains material—Moderately deformed patches of plains that 

are located on and around the margins of the Themis Regio rise. Type area: lat 28° 

S., long 276° E. Interpretation: Volcanic plains that formed early in the stage of 

development of the Themis Regio highland area that were subsequently deformed 

by rifting and (or) corona formation. May have originally emanated from coronae 

or fractures associated with rifting

Lineated plains material—Expanses of moderately deformed deposits, typically 

higher standing and embayed by mottled plains units; moderate occurrence of 

domes, cones, and shields; intersecting patterns of fractures and wrinkle ridges 

typical. Type area: lat 30° S., long 299.5° E. Interpretation: Volcanic plains that 

have undergone multiple episodes of volcanism and extension

Densely fractured plains material—Topographically complex, heavily fractured materials. Type area: lat 28° S., long 293.8° E. Interpretation: Volcanic plains units that 

have been warped and fractured by rifting and corona formation that may be related 

to the very early stages of formation of Themis Regio

IMPACT CRATER MATERIAL

Crater material, undifferentiated—Generally very radar bright floor, central peak, 

wall, rim, and ejecta materials. Type area: lat 38.5° S., long 274.8° E. Interpretation: Deposits and structures formed by hypervelocity impact

EXPLANATION OF MAP SYMBOLS

Contact—Dashed where inferred

Fault, lineament, fracture

Lineament—Associated with corona rim, typically fracture

Graben—Interpreted as extensional deformation

Wrinkle ridge—Interpreted as contractional deformation

Broad topographic ridge crest

Impact crater rim—Hachures on rim crest

Depression—Line marks top of slope. Hachures point downslope

Volcanic edifice (>5 km diameter)—Hachures at base of edifice

Steep-sided dome

Volcanic edifice (<5 km diameter)

Flow direction

Channel—Interpreted as formed by lava erosion

Surficial material—Radar-dark diffuse deposit

75°

50°

25°

75°

25°

–25°

0°

50°

0°

180° 210° 240° 270° 300° 330° 360°

–25°

–50° –50°

–75° –75°

V–1

V–29 V–30 V–28

V–40

V–62

V–41

V–27

V–26

V–15

V–14

V–16

V–39 V–42

V–18

V–51 V–54

V–17

V–53

V–60

V–6

V–5

V–19

V–50 V–55

V–31

V–38 V–43

V–7

V–59 V–61

QUADRANGLE LOCATION

Photomosaic showing location of map area. An outline of 

1:5,000,000-scale quadrangles is provided for reference.

V–52

–25°

–30°

–35°

–40°

–45°

–50°

285°

280°

275°

270°

290°

295°

285° 280°

275°

270°

290° 295°

300°

SCALE 1:4 711 886 (1 mm = 4.712 km) AT –25° LATITUDE

1:5 000 000 AT –34° and –73° LATITUDES

LAMBERT PROJECTION

500 400 300 200 100 0 KILOMETERS100 200 300 400 500

–50°

–40°

–25°

–30°

–35°

–45°

–25°

–30°

–35°

–40°

–45°

300°

–50°

Prepared on behalf of the Planetary Geology and Geophysics Program, 

Solar System Exploration Division, Office of Space Science, National 

Aeronautics and Space Administration

Cartography by Darlene A. Ryan

Manuscript approved for publication May 10, 2011

Descriptions of nomenclature used on map are listed at 

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

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/3165

Printed on recycled paper

Geologic Map of the Themis Regio Quadrangle (V–53), Venus

By

Ellen R. Stofan1 and Antony W. Brian2

2012

1

Proxemy Research, Rectortown, VA

2

University College, London, UK

Figure 2. Magellan topographic data of Themis Regio quadrangle (V–53), Venus.

Figure 3. Magellan rms slope map of Themis Regio quadrangle (V–53), Venus.

Figure 4. Magellan Fresnel reflectivity data for Themis Regio quadrangle (V–53), Venus.

Figure 1. Sketch map of major features in Themis Regio quadrangle (V–53), Venus, shown on base 

image. Major volcanoes (V) >100 km diameter are shown, as well as the 26 coronae (C). Approximate 

location of Parga Chasmata is shown, as well as Themis Regio (dashed line indicates approximate 

location of rise).

Figure 7. Magellan SAR image of northwestern Themis Regio 

quadrangle (V–53), Venus, illustrating the complex relations 

between corona and volcano flows. White arrow shows where 

Gertjon Corona flow material, member 1 (unit fG1), superposes 

flows from Mielikki Mons flow material, member 2 (unit fM2); black 

arrow shows where flows from Mielikki superpose Rigatona Corona 

flow material (unit fR).

Figure 6. Magellan SAR image of east-central Themis Regio 

quadrangle (V–53), Venus, illustrating the relations between 

Semiramus flow material, member 2 (unit fSe2), Tamiyo Corona 

flow material, member a (unit fTya), and Ukemochi Corona flow 

material, members a and c (units fUa and fUc). The flows associated 

with Semiramus are the youngest, overlying units fTya and fUa. 

Ukemochi and Tamiyo units have a complex relation, with unit fUc

superposed on unit fTya, which in turn is superposed on unit fUa. 

Contacts are shown as dashed so that unit relations can be seen.

Figure 5. Magellan SAR image of an unnamed channel on unit pm

in Themis Regio quadrangle (V–53), Venus. White arrows indicate 

where channel appears to be deformed; black arrow indicates where 

channel appears to cut and embay structures.

1.0 0.75 0.50 0.25 0.125 0.0

12.552 10 8 6 20 4 .2

RMS Slope (degree)

Corrected Reflectivity

240°

–25°

270°

–50°

240°

–25°

270°

–50°

240°

–25°

270°

–50°

0 50 KILOMETERS

272° 273°

–49.5°

–48.5°

295° 299°

–39°

–36°

276° 281°

–33°

–27.5°

0 50 KILOMETERS

0 50 KILOMETERS

C

C

C

C

C

C

C

C

C

C

C

C C

C

C

C

C

C

C C

C

C

C

V V

V

V

C

C C

V

270°

–25°

300°

–50°

*Units represent collections of distinct outcrops with local age-range constraints that have broad age ranges when viewed collectively.

6,048 6,050 6,052 6,055

Planetary radius (km)

Ts'an Nu

Mons

Maret

Xmukane

Corona

Kitna

Mielikki

Mons

Lilwani

Corona

Gertjon 

Corona

Obiemi 

Corona 

Angerona

Tholus

Anjea

Corona

Durga

Corona

Peck

Koinyt

Kwannon

Tholus

Justitia

Tholus

Santa 

Corona

Tacoma

Corona

Erigone 

Corona

Jocelyn

Elza

Hutash

Corona

Rigatona

Corona

Parvati

Corona

Shulamite

Corona

Latta

Corona

Themis

Regio

Sabin

Mertseger 

Mons 

fMe

plT

plT

vc

Zywie

Corona

Semiramus

Corona

Tamiyo

Corona

Ukemochi

Corona

Rohina

Tholus

Aksentyeva

Kenny

Abeona

Mons

Shiwanokia

Corona

Meiboia

Tholus

Ikas Coronae

Siduri

Mons

Chloris

Mons

Bibi-Patma

Corona

Navolga

Corona

Orbona

Corona

Nzambi

Corona

Bernadette

Partula

Corona

Nastya

Abington

Ama

Corona

Sinann

Vallis

Themis Regio

Parga Chasmata

Parga 

Chasmata

Prepared for the

National Aeronautics and Space Administration

Scientific Investigations Map 3165

Atlas of Venus: Themis Regio Quadrangle (V–53)

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey