2011

U.S. Department of the Interior

U.S. Geological Survey

Prepared for the National Aeronautics and Space Administration

Geologic Map of the Ganiki Planitia Quadrangle (V–14), Venus

By Eric B. Grosfils, Sylvan M. Long, Elizabeth M. Venechuk, Debra M. Hurwitz, Joseph W. Richards, 

Brian Kastl, Dorothy E. Drury, and Johanna Hardin

Pamphlet to accompany

Scientific Investigations Map 3121

75°

50°

25°

75°

25°

–25°

0°

50°

0°

90° 120° 150° 180° 210° 240° 270°

–25°

–50° –50°

–75° –75°

V–1

V–26 V–27 V–25

V–37

V–62

V–38

V–24

V–23

V–12

V–11

V–13

V–4

V–36 V–39

V–15

V–48 V–51

V–14

V–49 V–50

V–5

V–58 V–59

V–3 V–6

V–57 V–60

V–16

V–47 V–52

V–28

V–35 V–40

i

Contents

The Magellan Mission ..................................................................................................................................1

Magellan Radar Data ..........................................................................................................................1

Ganiki Planitia Quadrangle...........................................................................................................................1

Introduction ...........................................................................................................................................1

Mapping Techniques ...........................................................................................................................2

Unit Physical Properties .....................................................................................................................3

Unit Robustness ...................................................................................................................................3

Qualitative Evaluation ................................................................................................................4

Quantitative Evaluation ..............................................................................................................4

Map Units ..............................................................................................................................................5

Heavily Deformed Units .............................................................................................................5

Local Plains Units ........................................................................................................................6

Regional Plains Units .................................................................................................................8

Edifice and Corona Units ...........................................................................................................9

Impact Units .................................................................................................................................9

Discrete Landforms Within V–14 .......................................................................................................9

Canali ..........................................................................................................................................9

Major Volcanic Edifices ...........................................................................................................10

Smaller Volcanic Features ......................................................................................................12

Coronae ......................................................................................................................................13

Impact Craters ...........................................................................................................................14

Structural Deformation .....................................................................................................................15

Contractional Deformation ......................................................................................................16

Extensional Deformation .........................................................................................................16

Geologic History .................................................................................................................................17

Precursor ....................................................................................................................................17

Period 1 .......................................................................................................................................17

Period 2 .......................................................................................................................................18

Period 3 .......................................................................................................................................18

Cratering .....................................................................................................................................18

Discussion ....................................................................................................................................................18

Acknowledgments ......................................................................................................................................21

References ...................................................................................................................................................21

Tables

1. Summary of map unit properties within Ganiki Planitia (V–14) quadrangle, Venus ...................25

2. Individual map unit properties and names for every geographically distinct example of 

each unit, arranged alphabetically by map symbol and then by increasing area. ..........26

1

The Magellan Mission

The Magellan spacecraft orbited Venus from August 10, 

1990, until it plunged into the Venusian atmosphere on October 

12, 1994. Magellan Mission objectives included (1) improving 

the knowledge of the geological processes, surface properties, 

and geologic history of Venus by analysis of surface radar characteristics, topography, and morphology and (2) improving the 

knowledge of the geophysics of Venus by analysis of Venusian 

gravity.

The Magellan spacecraft carried a 12.6-cm radar system to 

map the surface of Venus. The transmitter and receiver systems 

were used to collect three data sets: (1) synthetic aperture radar 

(SAR) images of the surface, (2) passive microwave thermal 

emission observations, and (3) measurements of the backscattered power at small angles of incidence, which were processed 

to yield altimetric data. Radar imaging and altimetric and radiometric mapping of the Venusian surface were accomplished in 

mission cycles 1, 2, and 3 from September 1990 until September 1992. Ninety-eight percent of the surface was mapped with 

radar resolution on the order of 120 m. The SAR observations 

were projected to a 75-m nominal horizontal resolution, and 

these full-resolution data compose the image base used in 

geologic mapping. The primary polarization mode was horizontal-transmit, horizontal-receive (HH), but additional data for 

selected areas were collected for the vertical polarization sense. 

Incidence angles varied between about 20° and 45°.

High-resolution Doppler tracking of the spacecraft took 

place from September 1992 through October 1994 (mission 

cycles 4, 5, 6). Approximately 950 orbits of high-resolution 

gravity observations were obtained between September 1992 

and May 1993 while Magellan was in an elliptical orbit with a 

periapsis near 175 km and an apoapsis near 8,000 km. An additional 1,500 orbits were obtained following orbit-circularization 

in mid-1993. These data exist as a 75° by 75° harmonic field.

Magellan Radar Data

Radar backscatter power is determined by the morphology of the surface at a broad range of scales and by the intrinsic 

reflectivity, or dielectric constant, of the material. Topography at 

scales of several meters and larger can produce quasi-specular 

echoes, with the strength of the return greatest when the local 

surface is perpendicular to the incident beam. This type of scattering is most important at small angles of incidence, because 

natural surfaces generally have few large tilted faces at high 

angles. The exception is in areas of steep slopes, such as ridges 

or rift zones, where favorably tilted terrain can produce very 

bright signatures in the radar image. For most other areas, diffuse echoes from roughness at scales comparable to the radar 

wavelength are responsible for variations in the SAR return. In 

either case, the echo strength is also modulated by the reflectivity of the surface material. The density of the upper few wavelengths of the surface can have a significant effect. Low density 

layers, such as crater ejecta or volcanic ash, can absorb the 

incident energy and produce lower observed echo. On Venus, a 

rapid increase in reflectivity exists at a certain critical elevation, 

above which high dielectric minerals or coatings are thermodynamically stable. This effect leads to very bright SAR echoes 

from virtually all areas above that critical elevation.

The measurements of passive thermal emission from 

Venus, though of much lower spatial resolution than the SAR 

data, are more sensitive to changes in the dielectric constant 

of the surface than to roughness. As such, they can be used to 

discriminate between roughness and reflectivity effects. Observations of the near-nadir backscatter power, collected using a 

separate smaller antenna on the spacecraft, were modeled using 

the Hagfors expressions for echoes from gently undulating surfaces to yield estimates of planetary radius, Fresnel reflectivity, 

and root-mean-square (RMS) slope. The topography data produced by this technique have horizontal footprint sizes of about 

10 km near periapsis and a vertical resolution of approximately 

100 m. The Fresnel reflectivity data provide a comparison to the 

emissivity maps, and rms slope parameter is an indicator of the 

surface tilts, which contribute to the quasi-specular component.

Ganiki Planitia Quadrangle

Introduction

The Ganiki Planitia (V–14) quadrangle on Venus, which 

extends from 25° N. to 50° N. and from 180° E. to 210° E., 

derives its name from the extensive suite of plains that dominates the geology of the northern part of the region. With a 

surface area of nearly 6.5 x 106 km2 (roughly two-thirds that 

of the United States), the quadrangle is located northwest 

of the Beta-Atla-Themis volcanic zone and southeast of the 

Atalanta Planitia lowlands, areas proposed to be the result of 

large scale mantle upwelling and downwelling, respectively 

(see Bindschadler and others, 1992; Crumpler and others, 1993; 

Phillips and Hansen, 1998). The region immediately south of 

Ganiki Planitia is dominated by Atla Regio, a major volcanic 

rise beneath which localized upwelling appears to be ongoing (Bindschadler and others, 1992; Smrekar, 1994), whereas 

the area just to the north is dominated by the orderly system of 

north-trending deformation belts that characterize Vinmara Planitia (Zuber, 1987; Frank and Head, 1990). The Ganiki Planitia 

quadrangle thus lies at the intersection between several physiographic regions where extensive mantle flow-induced tectonic 

and volcanic processes are thought to have occurred.

The geology of the V–14 quadrangle is characterized 

by a complex array of volcanic, tectonic, and impact-derived 

features. There are eleven impact craters with diameters from 4 

to 64 km, as well as four diffuse “splotch” features interpreted 

to be the product of near-surface bolide explosions (see Ivanov 

and others, 1992; Schultz, 1992). Tectonic activity has produced 

heavily deformed tesserae, belts of complex deformation and 

rifts as well as a distributed system of fractures and wrinkle 

ridges. Volcanic activity has produced extensive regional plains 

deposits, and in the northwest corner of the quadrangle these 

plains host the initial (or terminal) 700 km of the Baltis Vallis 

canali, an enigmatic volcanic feature with a net length of ~7,000 

km that is the longest channel on Venus (see Baker and others, 
2

1992; Bray and others, 2007). Major volcanic centers in V–14 

include eight large volcanoes and eight coronae; all but one of 

these sixteen features was noted during a previous global survey 

(Crumpler and Aubele, 2000). The V–14 quadrangle contains 

an abundance of minor volcanic features including individual 

shield volcanoes and localized fissure eruptions as well as many 

small annular structures and domes, which often serve as the 

source for local lava flows.

The topographic and geophysical characteristics of the 

Ganiki Planitia quadrangle are less complex than the surface 

geology, but they yield equally valuable information about 

the region’s formation and evolution. Referenced to the mean 

planetary radius of 6051.84 km (Ford and Pettengill, 1992), the 

average elevation in the quadrangle is –0.26±0.86 km (2s) with 

a full range of –2.58 km to 1.85 km. The highest 2.5 percent 

of elevations in the quadrangle (above 0.60 km) are associated 

primarily with the major tessera blocks and the peaks of a few 

volcanic edifices, whereas the lowest 2.5 percent (below –1.12 

km) mostly occur within corona interiors and in the northwest 

corner of the quadrangle where the plains begin to merge into 

the Atalanta Planitia lowlands. At the ~4.6 km/pixel scale of 

the topography data, the mean point-to-point topographic slope 

is 0.63° and topographic slopes greater than 2° cover less than 

5 percent of the region. Overall, the topography of the Ganiki 

Planitia quadrangle can be characterized as flat, low lying, and 

nearly devoid of abrupt topographic variation. Complementing 

this gentle topography, the geoid anomaly has a generally linear 

gradient that decreases north-northwest from a high of ~20 m 

at the southern edge of the quadrangle (the northern border 

of the Atla Regio anomaly) to a low of –30 to –40 m along 

the northern edge (Konopliv and others, 1999). The vertical 

component of the gravity anomaly varies from ~50 mGal to –40 

mGal (Konopliv and Sjogren, 1994), and integrated analysis 

of the gravity and topography data indicates that dynamically 

supported regions and areas of thickened crust are both present 

within the quadrangle (McKenzie, 1994).

Because the Ganiki Planitia quadrangle is a plains-dominated lowland area that lies between several major physiographic provinces (namely, Atla Regio, Atalanta Planitia, and 

Vinmara Planitia), a geologic map of the region may yield 

insight into a wide array of important problems in Venusian 

geology. The current mapping effort and analysis complements 

previous efforts to characterize aspects of the region’s geology, 

for example stratigraphy near parabolic halo crater sites (Basilevsky and Head, 1995, 2002), volcanic plains emplacement 

(Basilevsky and Head, 1996), wrinkle ridges (Bilotti and Suppe, 

1999), volcanic feature distribution (Crumpler and Aubele, 

2000), volcano deformation (Lopez and others, 2008), coronae 

characteristics (Smrekar and others, 2003; Smrekar and Stofan, 

2003), lithospheric flexure (Barnett and others, 2002), and various features along a 30±7.58° N. geotraverse (compare Ivanov 

and Head, 1999; 2001; 2004). Our current research focuses on 

addressing four specific questions. Has the dominant style of 

volcanic expression within the quadrangle varied in a systematic fashion over time? Does the tectonic deformation within 

the quadrangle record significant regional patterns that vary 

spatially or temporally, and if so what are the scales, orientations and sources of the stress fields driving this deformation? 

If mantle upwelling and downwelling have played a significant 

role in the formation of Atla Regio and Atalanta Planitia as has 

been proposed, does the geology of Ganiki Planitia record evidence of northwest-directed lateral mantle flow connecting the 

two sites? Finally, can integration of the tectonic and volcanic 

histories preserved within the quadrangle help constrain competing resurfacing models for Venus (see Basilevsky and Head, 

1998; Nimmo and McKenzie, 1998; Phillips and Hansen, 1998; 

Guest and Stofan, 1999; Hansen, 2000)?

Mapping Techniques

The construction and analysis of the 1:5M scale map of 

the Ganiki Planitia quadrangle on Venus was performed using 

ArcView GIS software by ESRI, beginning with ArcView 3.1 

and ending in ArcView 9.2. Magellan Cycle 1 synthetic aperture radar (SAR) images, with incidence angles ranging from 

33.0–43.5° (Campbell, 1995), were used as the mapping base. 

Initial definition of map units was performed using full resolution 75 m/pixel FMAP images, mapped onto a Venus datum in 

sinusoidal projection, and standard mapping techniques (see 

Wilhelms, 1990) adjusted as necessary to accommodate both 

the interpretive challenges created when radar interacts with a 

planetary surface as well as the goals and scale of the mapping 

project (see Ford and others, 1989, 1993; Tanaka, 1994; Hansen, 

2000). Material units were defined principally on the basis of 

their relative radar backscatter properties plus superposition 

and crosscutting relationships, and synthetic stereo images 

(Kirk and others, 1992) with 10x vertical exaggeration proved 

particularly useful for resolving the interplay between plains 

units and topography and hence for contact characterization. 

Contacts are defined as either certain or uncertain. A contact 

labeled “certain” is normally characterized by a sharp transition 

between adjacent units, sometimes topographically controlled. 

This label is used conservatively, and is intended to denote a 

unit boundary we identify and locate with a high degree of confidence. In some instances, the robustness of a “certain” contact 

was tested by having multiple authors map the same area to 

assess whether different mappers would place the contact in the 

same location. A contact labeled “uncertain” is one that shows 

a high degree of variability in placement between mappers, 

one that connects two “certain” contacts across an area where 

the contact is less well defined, or one which is gradational or 

approximate in location. As an example of the latter, where 

thin deposits of pr2 onlap onto older pr1 materials in an area 

with very little topography, the demarcation between the two 

is ill defined and so constrained to a zone rather than a specific 

linear contact, and thus the boundary between the two is only 

placed in a general way. Once defined, the material units and 

contacts were digitally transferred to a 250 m/pixel SAR base 

map image, prepared by the U.S. Geological Survey (USGS) 

in Lambert Conformal Conic projection, and the robustness of 

the defined units was evaluated using additional georeferenced 

Magellan datasets obtained from the USGS, including altimetry, 

emissivity, reflectivity and RMS-slope data. Secondary datasets, 

such as point-to-point slope maps at the ~4.6 km/pixel resolution of the altimetry datasets, were also constructed for use 
3

during subsequent geological analysis. Major structural features 

were mapped at 250 m/pixel resolution, but interpretation of 

these features and the nature of their crosscutting and superposition relationships was enhanced through digital transfer 

onto the higher resolution sinusoidal imagery; such transfers 

within ArcView, including on-the-fly re-projection, can be 

accomplished through simple cut-and-paste operations, making 

integrated use of high resolution SAR imagery for interpretation 

and lower resolution data for the regional synthesis of information very straightforward. For clarity, not all mapped structural 

features are shown in the final map; instead, they are depicted 

in a representative fashion, largely limited to mapped structures 

greater than 30 km in length.

Two specific problems occurred during the mapping of the 

quadrangle. First, in some areas the structural deformation is so 

pervasive that it obscures the nature of the material unit being 

deformed as well as the presence of any pre-deformation material unit contacts; we define these regions as terrains. Second, 

several of the impact craters in the region are affiliated with 

extensive, radar-dark deposits that make it difficult to interpret 

the underlying material properties, contacts, and structures. This 

is particularly problematic for the radar-dark materials associated with the crater Yablochkina, which make the mapping 

process challenging across at least 0.88 x 106 km2 in the northern part of the quadrangle. Taken together, such crater-derived, 

radar-dark deposits cover ~1.2 x 106 km2 (~20 percent) of the 

mapped area.

Unit Physical Properties

Georeferencing and co-registration of different datasets 

within ArcView provides the opportunity to perform a more 

quantitative analysis of material unit properties than is possible 

within software products like Adobe Illustrator that are often 

used in planetary mapping. For instance, it is straightforward 

to calculate structural feature lengths and orientations, or to 

use map units as the basis for querying raster datasets, such as 

topography. This advantage is multiplied, however, because the 

form and transferability of the data allows future researchers 

who wish to conduct their own analyses using the mapped units 

to do so readily.

In past mapping studies, the remote-sensing properties of 

mapped units—backscatter, RMS slope, reflectivity, and emissivity—have normally been assessed using small “type” sample 

areas for a given unit. This approach is almost mandated for 

the incident angle-dependent backscatter because the data in 

the images must be corrected for their latitudinal position on a 

pixel-by-pixel basis before the backscatter from a given location 

or unit can be compared with another in a meaningful fashion. 

Most workers assess unit backscatter properties using software 

that adjusts a small selection of SAR image data for incidence 

angle and Muhleman calibration effects before ultimately yielding statistics for the selection in decibels (Campbell, 1995). This 

approach has the advantage that mappers can select areas they 

judge as representative and that lack structural deformation or 

other non-material artifacts that can locally alter the backscatter 

properties of the unit. However, there is some risk that the properties for the unit as a whole may not be well represented by the 

area(s) that are subjectively chosen, that non-material artifacts 

unrecognized by the mapper due to scale or other issues can still 

affect the backscatter, that little insight is gained into the degree 

of backscatter variability across the unit, and that the statistical 

error for the calculations is amplified by the small number of 

pixels typically sampled.

For our mapping and quantitative analysis of units within 

the V–14 quadrangle, we used ArcView to develop a simple 

(though computationally intensive) method for performing 

the same correction as Campbell (1995), thereby permitting 

location-specific, pixel-by-pixel conversion of backscatter to 

decibels across the entire quadrangle (Long and Grosfils, 2005). 

This approach has several advantages. First, by providing a 

chance to examine the entire material unit following conversion, we enhance the odds of identifying areas for sampling and 

analysis that are truly representative of the unit as a whole. This 

is particularly important when assessing the material characteristics of regional plains or other units that occur across a range 

of latitudes. Second, it may at times be advisable to eliminate 

the subjectivity involved with local sampling and instead simply 

calculate the material properties for a unit as a whole. Certainly 

this approach has the advantage that the large number of pixels 

sampled will enhance the robustness of the sampling. Third, it 

can provide a valuable, semi-quantitative opportunity to assess 

the degree to which, say, structural deformation has affected a 

unit. For example, an extensive regional plains unit with many 

obvious radar-bright structural features deforming it and a 

similar unit without much deformation will yield nearly identical mean backscatter values, but the standard deviation should 

be greater for the unit that has undergone deformation. Fourth, 

if bulk-material characteristics for a unit are desired without 

the contribution from non-material factors such as structural 

deformation, mapped structural features can be used (by buffering them in ArcView) as a basis for excluding deformed regions 

from the assessment of material properties; note that we did 

not take this step for our analysis here because it would have 

required far more detailed structural mapping than is suitable 

for a 1:5 million scale product. Performing a quadrangle-wide 

conversion of backscatter data can thus yield useful opportunities to complement and improve upon previous strategies for 

quantifying and comparing material unit properties. Material 

properties for the units and unit types in the Ganiki Planitia 

quadrangle are reported in tables 1 and 2, and backscatter variations are depicted in figures 1A and 1B.

Unit Robustness

A geologic map is meant to convey the mapmaker’s 

interpretation of the region depicted. If three people map the 

same area and then compare their results, it is likely that some 

percentage of their boundaries and unit definitions will be very 

closely matched, whereas other areas will bear little resemblance from one map to the next (see Waldron and others, 

2003). How, then, can one develop a sense of confidence that 

the material units being defined have robust qualitative and 

quantitative meaning?
4

Qualitative Evaluation

One approach, described in the previous section, is to use 

material unit properties to test whether units indeed appear to 

be different from one another, namely that the backscatter of 

materials mapped as a “radar-dark” plains units look more like 

one another than like materials mapped as “radar-bright” plains 

units. Whether subareas or entire units are sampled, however, 

the pixilated appearance inherent to radar backscatter data, and 

the natural variability in local surface properties within any 

given unit, often yield mean values that are indistinguishable 

from one another at a one standard deviation confidence level.

Another approach that can be used to gain confidence in 

a map product is to compare geologic map products prepared 

independently by different workers for the same area. This 

is particularly important for a global mapping effort because 

significantly different maps of the same or adjacent areas should 

raise concerns about how consistently a region’s geology can be 

interpreted. For the Ganiki Planitia quadrangle, four qualitative 

comparisons were conducted. In the first three, comparisons 

of the map unit boundaries at 180° E., shared with the V–13 

quadrangle (Ivanov and Head, 2005), at 210° E., shared with the 

V–15 quadrangle (J. Zimbelman, oral commun., 2003), and at 

50°N., shared with the V–5 quadrangle (Rosenberg and McGill, 

2001), reveal a high degree of consistency, with mapped unit 

boundaries and unit types/interpretations agreeing at approximately the 90–95 percent level; a map product for 25° N. 

(V–26) was not available at the time the current document was 

prepared. The principal differences identified stem from how 

a unit is or is not subdivided. For instance, in the V–14 quadrangle the Athena Tesserae are mapped as a single material unit 

because at 1:5 million scale the small handful of minor volcanic 

eruption products present within the tesserae are not significant 

enough to map as separate units. In the adjacent V–13 quadrangle, however, these kinds of erupted materials in Athena Tesserae were more significant and, therefore, they were mapped 

as separate units. Small variations in the way that features are 

“lumped” or “split” are common, and in general these variations 

do not result in significant differences in interpretation. For the 

fourth qualitative comparison, units mapped as part of a global 

30° N. geotraverse prepared by Ivanov and Head (2001) were 

compared to the current map of the V–14 quadrangle south 

of ~37.5° N. When the two sets of map units are compared, 

the map unit boundaries and types agree at approximately an 

80 percent level. The primary differences observed stem from 

either the manner in which the presence of structural deformation is incorporated into map unit definitions or from the differences in how features such as volcanic centers are characterized. 

Although interpretive differences that may be important occur 

in a few locations (for example, where we map the presence of 

large volcanoes that are not represented in the Ivanov and Head 

(2001) map), the general sense and location of material units in 

the two maps tends to be in reasonable agreement.

Quantitative Evaluation

The data presented in tables 1 and 2 (backscatter columns), 

along with the strong level of consistency between the Ganiki 

Planitia quadrangle map units and those defined by other workers, indicates that the map units we have defined are defensible. It is desirable, however, to test this confidence in a more 

quantitative fashion. Using the current map units as a “truth 

set,” and taking advantage of all physical property raster data at 

our disposal (namely, radar backscatter, elevation, slope, surface 

emissivity, and surface reflectivity), we employed a weighted 

model-based clustering (WMBC) method designed to identify 

units whose quantitative properties are aligned more closely 

with a unit type other than the one assigned during the mapping 

(Richards and others, 2010). Model-based clustering (Banfield 

and Raftery, 1993; Fraley and Raftery, 2002) uses the Expectation-Maximization (EM) (Dempster and others, 1977) algorithm 

to fit a mixture of multivariate normal distributions to a dataset 

by maximum likelihood. Model-based clustering via the EM 

algorithm has been shown to produce accurate and stable clusters in a variety of disciplines (Banfield and Raftery, 1993). We 

use it to demonstrate that the mapped units (which were mapped 

without using the quantitative information explicitly) are consistent with the final clustering output from a WMBC algorithm 

that uses quantitative data.

The quantitative data from the maps (namely, radar 

backscatter, elevation, slope, surface emissivity, and surface 

reflectivity) are available in pixels. Because (a) we are using 

this technique to validate the map, and (b) using pixel data in 

clustering algorithms can overwhelm the computing time, we 

use summary statistics from each individual unit (specifically, 

for each unit, the mean pixel value and the standard deviation of 

the pixel values) as variables in the WMBC. Because the units 

are of unequal size, we expect the larger units to have a higher 

degree of classification accuracy; that is, a unit with more pixels 

will have means and standard deviations that better approximate 

the true mean and standard deviation for a particular unit. A unit 

with relatively few pixels will be more difficult to map and will 

have data values that might not reflect the unit type as accurately as larger units of the same type. In the WMBC algorithm, 

the parameters for each type of unit (for example, the characteristics that define a volcanic region) are calculated based on 

the initial units identified as that type. Without weighting, small 

units and large units will contribute equally to the unit type 

parameters. To create a more stable model, we down-weighted 

small units and up-weighted large units so that the characteristics of any particular unit type were more resistant to deviations 

in small units. Our simulations show that weighted model-based 

clustering is superior to standard non-weighted model-based 

clustering for situations when units are of considerably different 

sizes.

The basic clustering algorithm starts with an initial partition of the data (the current “truth” map) and models the different unit types based on the quantitative characteristics. Then, 

units are freely reallocated to the unit type for which their likelihood is highest. The model of the unit type characteristics is 

then recomputed and units are again allowed to be reallocated. 

The process continues until all units are allocated to the unit 

type for which they have the highest likelihood.

The results from the statistical test demonstrate that most 

units remain classified the same way as specified by the original 

geologic map, meaning, for example, that all areas mapped as 
5

pr1 (see Description of Map Units on map sheet) quantitatively 

resemble one another rather than any of the other unit types 

mapped. On the basis of their statistical characteristics, fourteen 

units (7 percent of the total) with a net area of 0.47 x 106 km2

(~7 percent of the total) were consistently identified as misclassified, and for each case we re-examined the unit to determine if 

it had been mapped incorrectly. In all but one instance (a small 

tessera outlier reclassified as an edifice-fed flow unit), misclassification resulted when a geologically important piece of information integrated into definition of the unit during the mapping 

process was not picked up by the statistical algorithms. For 

instance, five units created by extensive eruption of lava flows 

from a low but sizeable central edifice (fe) were reclassified as 

regional plains units because in each instance the presence of 

the edifice topography was not significant enough for the statistical algorithms to distinguish the features quantitatively from 

flows lacking such an edifice as a source. Similarly, plains characterized by overlapping systems of eruptions from small (1- to 

20-km-diameter) shield volcanoes (ps) were in some instances 

reclassified as regional plains because the subtle morphology of 

the small shield volcanoes yields no quantitatively robust signature for the algorithm to recognize. While user insight is still 

required to examine any possible misclassifications, the strength 

of this statistical technique is that it uses available raster data to 

test the internal consistency of the map units.

Based on the suite of tests performed, we have a high 

degree of confidence in the material units we have defined using 

standard geological mapping techniques. The units are in good 

agreement with independently produced maps adjacent to and 

partially overlapping our map area, and each type of unit is 

statistically distinct from all the others when the full suite of 

quantitative data at our disposal is employed. It is important 

to recognize that other workers mapping the same quadrangle 

might produce a different map that is equally valid. We feel 

confident that the current map provides a scientifically sound, 

internally consistent basis for conducting a geologic interpretation of the quadrangle.

Map Units

Different conventions exist for discussing map units 

and presenting their stratigraphy. Here, closely following the 

approach of Brian and others (2005), we divide our unit descriptions into general categories (for example, plains materials) for 

clarity. Values listed for the elevation, backscatter, and other 

parameters are reported for the complete area covered by a unit, 

unless otherwise noted; detailed information is included in both 

table 1 (summary by unit type) and table 2 (information for 

each unit). A detailed summary of the map unit stratigraphy is 

provided below and in the Sequence of Map Units, and typical 

examples of all plains materials and those derived from volcanic 

edifices or coronae are depicted in figure 2.

Heavily Deformed Units

Roughly 0.39 x 106 km2 (5.9 percent) of the Ganiki Planitia quadrangle is occupied by complexly deformed regions 

called tessera terrain (unit t), characterized as radar-bright 

(–12.31 dB) materials so heavily deformed by at least two 

intersecting lineament sets that the precursor material(s) can no 

longer be recognized. Globally, tesserae occupy about 8 percent 

of the surface of Venus (Ivanov and Head, 1996), and in Ganiki 

Planitia each of the 56 blocks of tessera mapped is older than 

all other non-tessera units with which it is in contact. With a 

mean elevation more than 400 m above that of the quadrangle 

as a whole, tessera blocks uniformly exist as kipukas embayed 

by surrounding material units. Full accounting of the tessera 

structures is not performed for this 1:5 million scale mapping 

effort, but in general each tessera block is characterized by complex, short-wavelength, ridge-and-trough style deformation that 

is often uniform in nature within structural microterrains that 

can be similar to or different than the deformation preserved in 

adjacent microterrains. This deformation does not extend into 

the surrounding materials, with the possible exception in some 

places of fractures cutting unit pl (see “Local Plains Unit” section). The short-wavelength deformation is commonly punctuated by longer sets of fractures, troughs, graben and ridges that 

can be characterized well on a 1:5 million scale map, and our 

analysis of the tessera structures is thus limited here to a brief 

discussion of these features.

Parts of three major tessera terrains occur within the 

Ganiki Planitia quadrangle. The first, Nemesis Tesserae, 

occupies roughly 59 x 103 km2 in the northwest quadrant, 

principally as three major blocks 50- to 100-km wide by 200- to 

300-km long that together define a concave-north, east-west 

trending arc 1,400 km in length. The major structural lineaments across all three blocks have common characteristics, with 

one set comprised of extensional and contractional lineaments 

aligned roughly north-northeast and a second set comprised 

purely of extensional lineaments aligned roughly parallel to the 

local strike of the arc. The second major tessera terrain, Athena 

Tesserae, occupies roughly 63 x 103 km2 in the southwest 

quadrant, principally as one major equant block a few hundred 

kilometers across with 10 smaller outliers tentatively assigned 

the name Athena as well on the basis of their proximity to the 

main block. Unlike Nemesis Tesserae, however, the major 

structural lineaments do not show a common pattern from block 

to block. This absence challenges assignment of the outlying 

blocks as Athena Tesserae material, or it could indicate that 

deformation within Athena was diverse at a shorter spatial scale. 

The deformation within the largest block of Athena Tesserae 

is remarkably uniform, however, with one set of contractional 

lineaments trending northeast and a set of extensional lineaments trending west-northwest. The third major tessera terrain, 

Lahevhev Tesserae, occupies approximately 242 x 103 km2

in the south-central part of the quadrangle, principally as two 

main equant clusters of tesserae approximately 250 km by 500 

km in size. The first of these blocks, located ~500 km east of 

the main block of Athena Tesserae, preserves structural trends 

of the same orientation, although the majority of lineaments in 

both sets are extensional. It appears possible that this block is 

being destroyed by the processes creating plains units pLh and 

pLl (see “Local Plains Unit” section). The second block, a few 

hundred kilometers southeast, shows the same west-northwest 

and northeast-trending extensional lineaments but is also cut by 
6

a third dominant set of contractional structures with a northwest 

strike. Unlike the other tessera terrains, Lahevhev Tesserae has 

a strong positive residual topography signature indicative of 

a region of anomalously thick crust (McKenzie, 1994), which 

may help explain why Lahevhev preserves four times more 

material than the other major tessera terrains in the quadrangle.

While the blocks assigned to the three major terrains define 

the bulk of the tesserae in the quadrangle, twelve small tessera 

outliers ranging from a few hundred to a little over ten thousand 

square kilometers in size are sprinkled across the southeast, 

northeast, and northwest parts of the quadrangle. These outliers 

are too widely distributed and lack any common structural patterns to infer much about their origins. They are presumed to be 

remnants of larger tessera blocks that have been nearly obliterated by younger geological activity in the quadrangle, but the 

extent of these blocks is unconstrained by available data.

Deformation belt materials (unit bl) are highly elongate, 

heavily deformed regions which occupy 0.06 x 106 km2 (0.8 

percent), largely in the north-central and northeast parts of 

the Ganiki Planitia quadrangle. Like tessera, these units are 

characterized by a high degree of structural deformation, with 

both contractional (usually the earliest phases) and extensional 

deformation aligned along or slightly oblique to the gross trend 

of the belt as a whole. Locally, each is the oldest stratigraphic 

feature that has been preserved; in no area of the quadrangle are 

tessera terrain and deformation belt materials in direct stratigraphic contact, and the relative timing of these two units is 

unconstrained. Unlike tesserae, the deformation within unit bl

has not been sufficient to obliterate the precursor plains, but the 

materials deformed by the ridges and fractures within the belt 

are preserved as broad kipukas distinctly different from their 

surroundings; therefore, these kipukas warrant definition as a 

local map unit and, in combination with the density and nature 

of the deformation, as a distinct geomorphic map unit label. In 

other locations throughout the quadrangle, for example Akawa 

Dorsa and Fornax Rupes, belts of intense structural modification 

are not classified as unit bl because the precursor and surrounding plains materials are clearly a single unit.

Local Plains Units

The Ganiki Planitia quadrangle contains nine plains units 

defined on the basis of their relative radar and morphologic 

properties. Six of these units occur in local areas: lineated 

plains material (unit pl), hummocky Lahevhev plains material (unit pLh), lineated Lahevhev plains material (unit pLl), 

Ganis Chasma plains material (unit pG), shield plains (unit ps), 

and homogeneous plains (unit ph). The remaining three units 

form more extensive regional-scale deposits (units pr1, pr2, 

and pr3). All nine units have been deformed. In some instances 

the deformation crosscuts and is embayed by a given unit, 

which indicates emplacement and deformation of the material 

were occurring during the same time interval. In other cases, 

emplacement of a material unit appears to have been completed 

prior to the superposition of structural event(s).

Lineated plains material (unit pl; for an example see 37.6° 

N., 184.0° E.) occupies a net area of 0.33 x 106 km2 (5.1 percent 

of the quadrangle area) and the twenty small locations mapped 

range in size from ~400 square kilometers to 143 x 103 km2. In 

some locations, most occurring in the south half of the quadrangle, the unit is characterized by smooth, generally featureless 

material cut by a dense concentration of narrow extensional 

lineaments typically showing a uniform strike, although the lineament orientations are not constant from location to location. 

The majority of the mapped pl unit area, however, occurs within 

a discontinuous system of less deformed areas elevated above 

the surrounding regional plains and running east to west across 

the central part of the quadrangle. The majority of the deformation within these larger areas consists of east-west extensional 

structures (predominantly fractures) that trend roughly orthogonal to a much smaller number of contractional structures. Many 

small (<10 km in diameter) shield volcanoes are superimposed 

upon unit pl in these areas. In addition, unit pl defines the rims 

and near-rim areas of several coronae in the southeast corner of 

the quadrangle. All mapped locations exist as topographically 

elevated kipukas within younger surrounding terrains, and the 

average elevation of the unit is ~110 m above the mean for the 

quadrangle. The unit’s mean radar backscatter (–14.28 dB, compared to a quadrangle mean of –15.79 dB) reflects the nature of 

the unit as an intimate mixture of intermediate backscatter material and radar-bright lineaments. Interpreted as volcanic plains 

later deformed by both extensional and contractional structures, 

unit pl is older than every other plains unit with which it is in 

contact (units pr3, pr1, pr2, ps, and fe) and younger than the 

tessera terrain and deformation belt materials it abuts.

Ganis Chasma materials (unit pG) spatially associated with 

a major feature in the quadrangle, Ganis Chasma, occupy 0.16 

x 106 km2 (2.4 percent of the quadrangle) at a single location in 

the southwest corner of the quadrangle. Heavily deformed by 

the structures of the Ganis Chasma rift that cuts northwestward 

from Atla Regio, and aligned parallel to the rift’s trend, unit pG

has the strongest mean radar backscatter (–12.08 dB) of any 

material unit in the quadrangle. The source of the plains material is unconstrained—it does not visibly originate at either volcanic centers or rift structures within the quadrangle. The plains 

largely predate the structural deformation generated during the 

rifting event, but local small shield eruptions and a minor patch 

of unit pr2 (at 26.0° N., 186.0° E.) embay several rift lineaments; this embayment indicates that minor eruptions continued 

within the area after the majority of the rifting was completed. 

With a mean elevation more than 620 m above that of the quadrangle, unit pG also lies at the highest mean altitude of all the 

unit materials mapped. Lower elevation areas to the north and 

south are covered by regional plains units. Unit pr2 to the north 

embays unit pG and largely appears to cover the structures of 

Ganis Chasma, whereas unit pr1 to the south embays unit pG

but both covers and is crosscut by Ganis Chasma lineaments. 

Unit pG, interpreted as a volcanic plains unit that predates the 

Ganis Chasma rifting event, is preserved at elevation by uplift 

that occurred during the rifting process and is therefore older 

than all material units (units pr1 and pr2) with which it is in 

contact.

Lahevhev hummocky plains material (unit pLh) occurs in 

a single location, cutting east to west across the center of a large 

block of Lahevhev Tesserae. Centered at 28.3° N., 187.5° E. and 

covering an area of 12.5 x 103 km2 (~0.2 percent of the quad-
7

rangle), unit pLh is characterized by gentle undulatory topography that forms an interconnected system of elongate peaks and 

troughs with a wavelength of ~10 km. In local areas, patches of 

smooth, undeformed plains occupy the troughs, and these materials have a radar signature indistinguishable from the material 

that forms the undulatory topography. The elongation direction 

of the peaks runs parallel to the boundary of the unit, and a 

dense network of radar-bright fractures with a similar strike has 

deformed the unit in most areas. The density of these radarbright fractures appears to be largely responsible for the unit’s 

high mean backscatter of –12.21 dB. While unit pLh shows 

almost 2 km of total relief, on average it lies some 500–700 m 

below the elevation of the surrounding tesserae, and the mean 

is ~50 m below the mean for the quadrangle. Parts of Lahevhev 

Tesserae to the north and south of unit pLh, as well as a block 

of tessera surrounded by unit pLh, show late-stage extensional 

deformation that strikes orthogonal to the alignment of unit 

pLh. The persistent presence of these orthogonal lineaments 

within the adjacent tesserae and their absence within unit pLh is 

indirect evidence that unit pLh is younger than the tesserae, an 

interpretation also supported by local embayment relationships. 

The origin of the materials and fabric defining unit pLh remains 

uncertain, but the nature of the topography, structural deformation, and stratigraphic relations suggests that unit pLh may 

be the end product of a complex sequence of geologic events. 

Namely, unit pLh may be the result of an intermingled sequence 

of extension (to form the unit-parallel fractures and downdropped topography), volcanic eruption (to form the smooth 

plains materials in their deformed and undeformed states), and 

minor compression and/or shear (to generate the undulatory 

peak/trough topography) that has acted to rift apart and destroy 

a major block of Lahevhev Tesserae. Compared to the units 

with which it is in contact, superposition relations indicate that 

unit pLh is younger than the adjacent blocks of tessera (embays 

them, is not crosscut bv their structures), synchronous with unit 

pLl (no clear contact relations, and preserves the same structural 

deformation orientations and styles), and older than unit pr2

(embays unit pLh).

Lahevhev lineated plains material (unit pLl; for an example 

see 27.0° N., 190.0° E.), like unit pLh, lies adjacent to and 

between large blocks of Lahevhev Tessera terrain. Spatially the 

unit forms four mapped blocks covering an area of 0.15 x 106

km2 (~2.2 percent of the quadrangle), but two of these blocks 

have been subdivided into several pieces to call attention to 

key differences in their structural expression. Overall, unit pLl

lacks the gently undulating surface characteristic of unit pLh, 

and like unit pl it shows expanses of smooth plains deformed 

by a pervasively distributed network of fractures; locally, these 

fractures are dense enough to obscure the nature of the material they deform. The fractures are commonly collected into 

narrow, slightly sinuous bands tens to hundreds of kilometers 

in length that are co-aligned with the dense lineaments seen 

in unit pLh, and both the structures and plains material are 

gradational across the inferred boundary between these two 

units; these characteristics cause us to interpret their formation 

as synchronous. Topographically, unit pLl lies at a mean elevation nearly 400 m above that of the quadrangle, and it defines 

a rough, deformed planum at an altitude exceeded only by the 

mean elevations of the tesserae and unit pG, the Ganis Chasma 

plains material. The strong radar backscatter (–12.41 dB) of unit 

pLl is similar only to the backscatters characteristic of the most 

tectonically modified materials in the quadrangle (namely, units 

t, pLh, and pG), and it therefore reflects the highly deformed 

nature of the unit. Interpreted as an elevated expanse of volcanic 

plains fractured by oblique extension, unit pLl is younger than 

adjacent blocks of tessera, is synchronous with unit pLh, and is 

older than units pr1 and pr2.

Shield plains material (unit ps; for an example, see 44.25° 

N., 197.5° E.), mapped at 17 locations scattered across the 

quadrangle, covers 0.55 x 106 km2 (8.4 percent of the quadrangle). Unit ps has a high density of local surface flows erupted 

from vents at the apices of small, low-relief topographic cones 

interpreted as shield volcanoes (edifices less than 20 km across), 

which often gives the unit ps plains materials a mottled appearance. High densities of small shield volcanoes occur elsewhere 

in the quadrangle, but the defining characteristic of unit ps

is that the flows from the numerous small shields and vents 

overlap sufficiently to be the predominant source of the plains 

material across an area exceeding 1,000 square kilometers. The 

mean elevation of the unit is within 50 m of the mean for the 

quadrangle, and thus the two mean elevations are indistinguishable given the vertical precision of the altimeter. Similarly, the 

mean radar backscatter for unit ps, –16.36 dB, is only slightly 

lower than the mean for the quadrangle as a whole (–15.79 dB). 

Stratigraphically, based on embayment and crosscutting relations, unit ps materials predate the deposits from unit ph and 

the unit fe materials from the only volcanic center to which they 

are adjacent (Dutrieu Patera), but they postdate all other material units with which they are in contact (units pr3, pr1, pr2, pl, 

bl, co, and t); the timing of emplacement of cof materials from 

Nimba Corona is uncertain. These relations establish unit ps

as one of the youngest in the quadrangle, a result at odds with 

findings which suggest that shield plains are a widespread unit 

that formed early in the stratigraphic sequence of many areas 

(see Basilevsky and Head, 2000; Ivanov and Head, 2004, and 

references therein). Some caution is warranted in any interpretation of this type of unit, however, because unit ps is defined by 

extensive sequences of small, overlapping volcanic deposits, 

and only the timing along the borders of the mapped material regions are well constrained. If a 20-km-diameter value is 

assumed to be typical for a small shield and its local deposits, 

then one can calculate to first order the area of unit ps, which 

contains small shields that do not lie in contact with other material units. Half of the small shield volcano deposits of unit ps

in the Ganiki Planitia quadrangle are not in contact with other 

material units, and because the available stratigraphic information is not generally sufficient to unravel the internal chronology 

of small shield emplacement in detail within each mapped area 

of unit ps, the stratigraphy within the interiors of these units is 

poorly constrained at best.

Homogeneous plains material (unit ph) occurs in only one 

location (44.5° N., 193.5° E.) and covers an area of 0.01 x 106

km2, or ~0.2 percent of the quadrangle. Lying at an elevation 

roughly 340 m above the quadrangle mean, the unit has a low 

radar backscatter (–19.45 dB) and is characterized by a rounded 

geometry, feathery margin, and lack of internal texture. Strati-
8

graphically, the unit is younger than units t, pr2, and ps with 

which it is in contact, and interactions with older structures suggest that the unit varies in thickness. The basic geologic observations (feathery edges, mantling appearance, and association 

with young volcanic features) are not strongly consistent with 

lava flow emplacement, nor are the remote-sensing material 

properties (which indicate a very rough surface characterized 

by competent rock) consistent with an unconsolidated aeolian 

deposit (see Campbell and others, 1998). Taken together, however, the basic characteristics of the unit are such that we have 

interpreted unit ph as a possible pyroclastic flow deposit (Long 

and Grosfils, 2004). Although no source vent is evident, it is 

possible that the materials are locally derived, which implies 

the vent has been buried. It is also possible that the materials originated upon and flowed down the flanks of the large, 

unnamed volcanic rise (500 km in diameter and characterized 

by a fanning dike swarm, abundant small shield volcanism, and 

extensive sets of long lava flows plus unit ph) centered just east 

of the deposit. Because most models predict that a minimum 

of ~1.5–5.0 wt. percent CO2 is necessary to create sufficient 

basaltic magma disruption for pyroclastic volcanism to occur on 

Venus (see Grosfils and others, 2000), it appears that the latest 

stage of local volcanic activity in the region was characterized 

by an unusually high concentration of volatiles.

Regional Plains Units

The Ganiki Planitia quadrangle has three major regional 

plains units: pr1, pr2, and pr3. The oldest of the three, regional 

plains material 1 (unit pr1), covers 0.86 x 106 km2 (13.1 percent 

of the quadrangle; for an example, see 34.25° N., 195° E.) and 

is mapped at 14 locations, all of which occur in the south half 

of the quadrangle. The unit has a mean elevation ~180 m higher 

than the quadrangle as a whole, and the mean backscatter of 

–13.62 dB also indicates a somewhat rougher surface than the 

norm. Unit pr1 has, relative to the other regional plains materials, a highly blotchy appearance. The plains are distinctive in 

this sense, displaying stratigraphically variable contact relations 

that are often ambiguous locally, but, when viewed collectively, 

indicate the unit has undergone a prolonged history of spatially 

and temporally patchy emplacement and modification. Based on 

the major lineaments mapped, the deformation preserved within 

unit pr1 consists of twice as much extensional deformation as 

contractional by net lineament length, including the long array 

of complex fracturing that defines Fornax Rupes; extensional 

and contractional deformation are 1.7x and 1.4x more concentrated per unit area than the quadrangle mean (for details of 

this calculation, see “Structural Deformation” section). Where 

they are in contact, unit pr1 material is younger than tesserae, 

lineated plains unit pl, unit pLl, and unit pG. They overlap in 

age with unit pr2 in a few locations but are generally younger; 

they also interfinger stratigraphically with the structural 

deformation that defines Ganis Chasma. Unit pr1 materials are 

older than unit ps and the lobate flow deposits from all named 

(Ninisinna Mons, Nimba Corona, Garland Patera, Kokyanwuti 

Mons (V–15), and the Waka Mons/Asintmah Corona complex) 

and unnamed volcanic centers (unit fe) they abut. Interpreted as 

an early formed suite of volcanic plains that has been preserved 

at many locations due to its higher-than-average elevation (for 

example, see 31.0° N., 182.0° E.), unit pr1 provides a unique 

record of the complex volcanism and tectonism characterizing 

the early plains and history of the quadrangle.

The second era of regional plains emplacement is defined 

by regional plains material 2 (unit pr2), a smooth, flat, generally 

featureless material that covers 2.66 x 106 km2 (40.4 percent) 

of the V–14 quadrangle; for an example, see 40.5° N., 199° E. 

There are 25 mapped locations. One of these, occupying the 

west half of the quadrangle, accounts for 73 percent of the unit 

area. Three of the remaining 24, which lie within the central 

and northeastern parts of the quadrangle, define most (~22.7 

percent) of the remainder. Unit pr2 has a mean elevation ~110 

m below that of the quadrangle (~300 m less than unit pr1), and 

with a mean backscatter power of –17.84 dB it is one of the 

smoothest materials mapped. Emplacement of the unit appears 

to have occurred over a prolonged interval and, though unit pr2

is younger than unit pr1 in most locations, at a few the two are 

clearly contemporaneous. Unit pr2 postdates tesserae, deformation belts, and the more heavily deformed plains (units pl, pLh, 

and pLl); is locally synchronous with but generally younger 

than unit pr1; is locally synchronous with but generally older 

than unit fe; and predates all unit ph, ps, and pr3 materials with 

which it is in contact. In the northwestern part of the quadrangle, unit pr2 materials are cut by the Baltis Vallis channel. 

Structurally, unit pr2 preserves approximately equal amounts 

of extensional and contractional deformation by net lineament 

length, and extensional and contractional deformation are 1.1x 

and 1.4x more concentrated per unit area than the quadrangle 

mean. Embayment relations with other material units and 

superposition of unit pr2 locally on different lineament sets 

both indicate that unit pr2 is a fairly thin deposit, and the unit is 

interpreted as smooth, low viscosity volcanic deposits that currently occupy many of the lower elevations of the quadrangle.

The final phase of widespread plains emplacement is 

characterized by regional plains material 3 (unit pr3), which lies 

at a mean elevation 450 m below the average for the quadrangle 

(~350 m below unit pr2). Unit pr3 has a radar backscatter 

(–15.46 dB) almost indistinguishable from that of the quadrangle as a whole. Mapped at 12 locations, predominantly in the 

northeast quadrant of V–14, unit pr3 covers 0.61 x 106 km2 of 

the quadrangle (9.3 percent; for an example, see 44° N., 205.25° 

E.). Stratigraphically, unit pr3 materials are older than unit ps

and most volcanic centers (except Xtoh Mons) where these 

units are in contact. Unit pr3 also postdates tesserae, deformation belts, and all other units with which it in contact (units pl, 

cof, and pr2). Most (86 percent) of unit pr3 occurs as a single 

continuous area with no evident source. Onlap relations reveal 

that this major unit pr3 locale is thicker in the middle and thin 

at the edges. The other small patches of unit pr3 generally 

have identifiable sources (a small volcano, for instance) but 

are similar in stratigraphic position. In the northwestern part of 

the quadrangle, a small deposit of unit pr3 has flowed into and 

along the Baltis Vallis channel. Structurally, unit pr3 preserves 

nearly four times as much contractional deformation as extensional by net lineament length, and extensional and contractional deformation are 0.43x and 2.3x more concentrated per 

unit area than the quadrangle mean. Unlike the older pr1 and 
9

pr2 plains units, each location of unit pr3 materials appears to 

define a stratigraphically brief, possibly single, emplacement 

event, and the unit is interpreted as young, somewhat rough, 

wrinkle-ridge-deformed volcanic plains deposits that currently 

occupy most of the lowest elevation areas in the quadrangle.

Edifice and Corona Units

In addition to volcanic plains, the Ganiki Planitia quadrangle contains an array of volcanic features including canali, 

major volcanic centers (of types mons, patera, tholus, corona, 

and unclassified; for definitions see http://planetarynames.

wr.usgs.gov/index.html), and small volcanic edifices and domes. 

Some of these are responsible for the emplacement of material 

units preserved at the surface, whereas others are not. Here we 

describe the material units. Detailed descriptions of the discrete 

volcanic landforms are presented later, and stratigraphic placements are depicted on the Sequence of Map Units.

Volcanic edifice flow materials (unit fe), interpreted as 

volcanic lava flows originating at major edifices, cover 0.66 

x 106 km2 (10.0 percent of V–14; for an example, see 40° N., 

206° E.). The average elevation of unit fe is within a few tens 

of meters of the mean for the quadrangle, and at –14.69 dB 

its average radar backscatter is slightly greater than that of the 

quadrangle as a whole. In general, the named and unnamed unit 

fe materials preserved at the surface are among the youngest 

in the quadrangle, and each named volcanic center is described 

herein. In cases where a specific example of material unit fe is 

constrained to originate at a named volcanic center, we have 

used arrows on the map to denote lava-flow directions away 

from the center.

Most coronae in the quadrangle are characterized by 

displacement and deformation of older surrounding plains, 

and they have failed to emplace distinct material units of their 

own. There are, however, some exceptions to this general 

rule. Corona rim materials (unit co) are older, uplifted plains 

materials, occupying 34 x 103 km2 (~0.5 percent of V–14), and 

they are characterized by a backscatter (–15.69 dB) and mean 

topographic elevation similar to the quadrangle averages. These 

plains were mapped as a separate material unit when preserved 

in isolation upon elevated topography that has subsequently 

been embayed by younger material units. Structurally, unit co

is deformed by a series of gentle, annulus-parallel contractional arches cut by contractional and extensional lineations. In 

addition, in two instances a corona has produced corona flow 

materials (unit cof), defined as smooth and generally featureless 

plains with a mean backscatter of –15.05 dB and a mean elevation ~200 m below the quadrangle mean. Based on observed 

geologic and geographic relationships, we interpret unit cof

as lava flows derived from a nearby corona, and in total unit 

cof covers an additional 58.4 x 103 km2 (~0.8 percent) of the 

quadrangle.

Impact Units

Impact crater formation within the quadrangle has produced two distinct material units. The first, present at every 

impact site, consists of crater material, undifferentiated (unit 

c). This material, covering 20.3 x 103 km2 (~0.3 percent of 

the quadrangle), is characterized by a hummocky texture and 

irregular margins that together define the crater rim, interior 

walls and floor, and ejecta. As expected, the blocky nature of the 

surface materials yields a high mean backscatter (–13.24 dB), 

and on average the craters occur at a mean elevation (–340 m) 

that is quite low relative to the quadrangle mean. The largest 

crater in the quadrangle, Yablochkina, is also surrounded by a 

limited array of deposits mapped as crater flow material (unit 

cf), which has the lowest radar backscatter in the quadrangle 

(–20.52 dB mean). Characterized by a sheet-like geometry and 

arcuate, sharply defined margins, unit cf lies at a mean elevation 

of –130 m, and it appears be superimposed on the surrounding regional plains. The characteristics of unit cf are distinctly 

different than those of the dark halo deposits with which many 

of the impact craters are also associated; the dark-halo deposits 

are not a material unit, and we describe these deposits in detail 

herein when discussing the characteristics of each discrete 

impact crater.

Discrete Landforms Within V–14

Canali

Canali remain one of the most enigmatic volcanic features 

on Venus. As sinuous channels a few kilometers in width and 

many hundreds or thousands of kilometers long, it has been 

proposed that canali are produced when volcanic materials 

moving above or below a pre-existing plains surface generate 

a channel via thermal and/or mechanical erosion (see Baker 

and others, 1992; Gregg and Greeley, 1993; Lang and Hansen, 

2006; Waltham and others, 2008). The northwest quadrant of 

the Ganiki Planitia quadrangle contains the initial (Baker and 

others, 1992) 700 km of Baltis Vallis, the longest channel of 

any kind (net length >7,000 km; Bray and others, 2007) thus 

far identified in the Solar System. The channel cuts materials of 

unit pr2 and is partially filled in by younger unit pr3 materials. 

It follows a northward course that is generally down gradient 

(regional slopes range from a few tenths to hundredths of a 

degree) but does not respond to gentle topographic undulations tens of kilometers wide, hundreds of kilometers long, and 

hundreds of meters tall. Similarly, the channel does not respond 

to the presence of local structural deformation, which is clearly 

younger where the two intersect. The channel width varies from 

1.5 to 4.5 km, and it is mapped in four segments. Three of these 

segments form a braided system separated by breaks of at most 

a few kilometers, possibly caused by later structural or volcanic 

activity, whereas the fourth is separated from the others by ~100 

km. The most direct path between the braided components and 

this fourth segment aligns with and is heavily deformed by a 

large wrinkle ridge—these relations indicate that all four segments might once have been connected. No source region for 

the channels is evident. The southernmost ends of the braided 

and fourth segments are 150 km north and 180 km east-northeast, respectively, from Nijole Mons, and it has been proposed 

previously (Baker and others, 1992) that this volcano may be 

the source region for Baltis Vallis. This proposed hypothesis 
10

is not supported by our mapping efforts, because there is no 

evidence to suggest that either younger volcanic deposits or 

structural deformation has affected the area separating the edifice and channel ends. The fourth segment ends adjacent to the 

major, previously unrecognized volcanic rise associated with 

unit ph, however, and it is possible that this rise is linked to the 

origin of the canali as it is similar in stratigraphic position and is 

located fairly close by.

Major Volcanic Edifices

There are materials from ten named volcanic centers within 

the Ganiki Planitia quadrangle, including one tholus, four 

patera, and five mons. Individually they cover areas from 18 to 

214 x 103 km2, and each is described separately herein.

Apakura Tholus (40.3° N., 208.8° E., diameter 10 km) 

is a small, domical volcanic edifice that has erupted materials 

of unit fe that cover more than 64 x 103 km2 (~1.0 percent of 

V–14). With a mean elevation 500 m below that of the quadrangle, the Apakura Tholus materials have a total relief of 1,100 

m and a radar backscatter close to the mean for the quadrangle 

(–15.79 dB). Lobate and sheet flows define a broad, roughly circular stack of material extending 120 to 170 km from the central 

vent area, with a longer set of lobate flows extending nearly 

400 km to the east. Apakura Tholus flows embay unit pr3 to the 

north, east, and west and are, in turn, embayed by flows from 

Shala Mons to the south. The dominant north-south wrinkle 

ridges that cut unit pr3 in this area both deflect and crosscut the 

Apakura Tholus flows, and these relations indicate that formation of this structural set and eruption of the Apakura Tholus 

lavas were contemporaneous events.

The Ganiki Planitia quadrangle contains four patera. Two 

of these, named prior to the current mapping effort, are not the 

source of any specific surface materials. Izumi Patera (50.0° N., 

193.6° E.), which lies at the northern boundary of the quadrangle, is recognizable due to the presence of a 15- to 20-kmwide topographic annulus some 75 km in diameter, which rises 

300 m above the depression it encloses and 300 to 400 m above 

the surrounding plains. In fact, Izumi somewhat resembles 

a small corona; however, it shows only minor contractional, 

circumferential deformation along the inner and outer edges 

of the annulus. The topographic deformation has uplifted the 

unit pr2 materials exposed throughout the area and therefore 

Izumi postdates unit pr2 at this location. Razia Patera (46.2° 

N., 197.8° E.) is also comprised of, and thus younger than, 

unit pr2 materials, and like Izumi it has many characteristics in 

common with coronae. Peanut-shaped overall, the long axis of 

Razia Patera extends 150 km north-south and 50 km east-west. 

Topographically, the 20- to 35-km-wide rim of the patera rises 

200 to 400 m above the enclosed depression, but it also has a 

distinct structural signature, with extensional lineaments aligned 

tangential to the rim while short contractional structures, confined to the elevated annulus topography, are aligned normal to 

the rim. Based on deflection of regional wrinkle-ridge sets into 

a pseudo-radial alignment as they approach Razia Patera, this 

volcanic feature was present prior to the contractional deformation that crosscuts unit pr2. Unit pr3 abuts against the annulus 

topography to the south and, while numerous small shields 

occupy the center of the patera, its floor is covered predominantly by unit ps materials that have flowed into the central 

depression via a breach located in the southwestern part of the 

annulus.

Dutrieu Patera (33.8° N., 198.5° E.), like Razia Patera, is 

peanut-shaped, and it extends 150 km north-northeast by 75 km 

west-northwest. Surrounded by a topographic annulus 200- to 

500-m tall and 20- to 35-km wide, the interior of the patera lies 

200 to 600 m below the level of the surrounding unit pr2 and 

unit ps plains materials. The mean elevation of the Dutrieu 

Patera deposits is 120 m below the mean altitude of the quadrangle, and the relief of 1.3 km extends from 800 m below the 

mean to 500 m above it. The annulus and interior of the patera 

consist of lobate and sheet materials of unit fe with a mean 

backscatter of –14.66 dB; together these materials cover 30.4 

x 103 km2 (~0.5 percent of V–14). Initial eruptions from the 

patera thus predate formation of the annulus and central depression, and this finding suggests that a complex interplay between 

volcanic activity and topographic adjustments was required to 

form the final patera morphology. Based on crosscutting and 

embayment relations, the unit fe materials defining the bulk of 

the patera are embayed to the south and west by unit pr2. These 

same unit pr2 plains are themselves embayed by unit fe materials, erupted from the outside edge of northern Dutrieu Patera, 

which extend 150 to 175 km east and west from the inferred 

eruption site and partially wrap around the patera topography. 

To the west, the older unit fe flows of Dutrieu Patera are in 

contact with extensive unit ps plains materials; stratigraphic 

timing information along this contact is sparse but indicates 

interfingered emplacement of the two units, with most of unit 

fe predating most of unit ps. The younger flows from Dutrieu 

Patera, however, are clearly superimposed upon unit ps. Taken 

together, these data indicate that Dutrieu Patera was a long-lived 

volcanic center emplaced during an interval that encompasses 

the same period of time over which local unit pr2 and unit ps

materials were forming.

Garland Patera (32.7° N., 206.8° E.), the smallest of the 

four patera within the Ganiki Planitia quadrangle, is characterized by a mean elevation identical to that of the entire quadrangle and a 40- to 45-km-diameter annulus of fractures; a 

faint outer network of circumferential fractures extends at least 

another 40 km to the southeast, however, defining a broader, 

egg-shaped pattern of deformation. The main annulus, coinciding coarsely with a topographically elevated rim 10- to 

15-km wide that rises 400 m above the mean elevation of the 

unit, surrounds a depressed area that extends 500 m below 

the surrounding plains; these relations create nearly a kilometer of local relief. Surrounding the annulus, rough lobate and 

sheet materials of unit fe with a mean backscatter of –12.57 

dB extend 80–100 km to the northeast, southeast, and southwest, covering 18.4 x 103 km2 (0.3 percent of V–14). Based on 

observed superposition and crosscutting relations, the Garland 

Patera unit fe materials are everywhere superimposed upon 

the surrounding pr1 unit, and in most locations the structural 

features that deform unit pr1 also terminate at the contact or 

a short distance into the fe unit. However, several northwesttrending wrinkle ridges, north-south-trending fractures, and the 

bulk of the fine-scale extended annular deformation crosscut 
11

unit fe unit locally; these characteristics suggest that several 

minor episodes of deformation postdate the interval during 

which the bulk of unit fe was emplaced. Taken together, these 

data indicate that Garland Patera is a volcanic center that postdates the bulk of the adjacent regional plains emplacement and 

deformation, although there are clear indicators that externally 

driven regional deformation as well as late-stage endogenic 

deformation (perhaps the initial phases of a larger collapse) also 

occurred within the feature to a limited extent.

The Ganiki Planitia quadrangle contains five montes, only 

one of which (Nijole Mons, see Burba and others, 2001) had 

previously been named. The main Nijole Mons edifice (45° N., 

185° E.), circular in plan view, has ~1,250 m of domical relief 

across a diameter of 60 km, and a small secondary dome 20–25 

km across occupies its summit position. Owing to its spatial 

coincidence with Akawa Dorsa it is difficult to tell how much 

of the edifice is constructional and how much derives from the 

arched topography of the underlying Dorsa. The apron of unit 

fe materials surrounding Nijole Mons out to a distance of ~50 

km beyond the main edifice is also unusual, characterized by 

a wispy appearance and a very low backscatter (–17.10 dB). 

The contact between these materials and the adjacent unit pr2

lowland plains, also mottled and characterized by low radar 

backscatter, is poorly defined, and the apron is not marked by 

any other distinctive physical properties (for example, emissivity); at most the Nijole Mons materials cover 18 x 103 km2

(~0.3 percent of V–14). We interpret the wispy materials as 

thin, sheet-like lava flow deposits, while noting that an explosive emplacement mechanism, although unlikely, cannot be 

ruled out. If the lava flow interpretation is correct, the apron of 

Nijole Mons flows is superimposed upon unit pr2 yet is clearly 

crosscut by the wrinkle ridges within Akawa Dorsa and the surrounding plains; these relations indicate that much of the local 

structural deformation within the Dorsa postdates the formation 

of Nijole Mons.

In sharp contrast to Nijole Mons, Ninisinna Mons (25.7° 

N., 197.5°E) is surrounded by a complex sequence of lobate, 

high backscatter (–11.97 dB) unit fe materials that cover an area 

of 30.7 x 103 km2 (~0.5 percent of V–14). The central, heavily 

deformed edifice is surrounded by an annulus of fractures some 

100 km in diameter. The lobate unit fe materials originate both 

at and from within the interior of this circumferential feature, 

and the stratigraphy indicates that the annular deformation and 

emplacement of the lobate flow materials overlapped in time. 

The region within the annulus is elevated as much as 2.5 km 

above the area outside it, and the average elevation of the Mons 

and associated unit fe materials is 590 m above the mean for the 

quadrangle. The lobate apron of flows is superimposed upon or 

abuts against the surrounding unit pr1 plains, adjacent parts of 

Lahevhev Tessera, a set of unit fe materials 100 km to the south 

(the source of these flows appears to be external to the quadrangle or obscured by gaps in the radar coverage), and upon a 

second set of unit fe plains 200 km to the north. The second set 

of fe plains are inferred to originate from a set of three or four 

small volcanic centers in that area, and the similarity between 

the characteristics of these smaller centers and Ninisinna Mons, 

particularly structurally and topographically, suggests that they 

may share a common volcanic heritage. Finally, the lobate 

apron and edifice are crosscut by younger structural lineaments 

that define the southernmost extent of Fornax Rupes within 

the quadrangle. We thus infer that Ninisinna Mons is the most 

recent feature constructed within a broader area characterized 

by a persistent, self-similar style of volcanic activity, and that 

this period of volcanism from local centers postdates regional 

plains emplacement but predates the tectonic activity responsible for creation of the younger Rupes. 

Shala Mons (39.4° N., 208° E.) is a flat, minimally 

deformed volcanic edifice 90 km across that has erupted materials of unit fe covering more than 58 x 103 km2 (~0.9 percent 

of V–14). With a mean elevation 460 m below that of V–14, 

the low-lying Shala Mons deposits have a total relief of 1,300 

m and a radar backscatter (–15.01 dB) only slightly greater 

than that of the quadrangle as a whole. Lobate and sheet flows 

extend significant distances to the east (>175 km), south (~220 

km), and west (~650 km), and there are subtle topographic 

indications that an arcuate or ovoid annulus 50–60 km across 

has been almost completely buried by the flows just south of 

the volcano’s crest. The flows to the south and east are superimposed upon unit pr3 and unit pr2 materials as well as sheet-like 

unit fe deposits that appear to originate from Kokyanwuti Mons 

in the adjacent V–15 quadrangle. To the north, late-stage flows 

from Shala Mons are superimposed on Apakura Tholus; the 

flows’ failure to extend more than 75–100 km in this direction 

is inferred to be a result of abutment against the pre-existing 

Apakura Tholus topography. Finally, the narrow, laterally 

extensive flow deposits to the west occupy the topographic low 

between Apakura Tholus and an unnamed sequence of small 

volcanic centers forming a linear ridge that extends northwest 

from Madalait Corona. The narrow Shala Mons flows crosscut 

or embay unit pr3 and unit pr2 materials, and they also abut a 

sequence of unit fe materials that are spatially correlated with 

the linear array of volcanic centers and are inferred to originate 

from them; however, the nature of the stratigraphic contacts 

between the two fe units leaves their relative timing uncertain.

Waka Mons (26.3° N., 207.7° E.) is perhaps the most 

distinctive and unusual edifice within the quadrangle. The main 

edifice, roughly 1,000 m high and 50–60 km in diameter, is 

superimposed upon the northern rim of Asintmah Corona. A 

complex system of lobate flows clearly emanates from Waka 

Mons, and it extends about 200 km in all directions. These 

lobate flows were preceded by sheet-like deposits that cover the 

surrounding plains across radial distances extending as much 

as 500 km. It is unclear whether these sheeted flows derive 

from Waka Mons or Asintmah Corona, and they have thus 

been mapped in combination with the lobate flow sequence as 

a single unit fe, which has a mean backscatter of –14.84 dB. 

This unit covers 213 x 103 km2 (~3.2 percent of V–14), but it 

also extends significant distances into V–15, V–26, and V–27, 

and we estimate that the net area of the deposits could be twice 

that of the exposure within V–14. Within the V–14 quadrangle, 

this fe unit embays all others with which it is in contact (units 

fe, pl, pr3, pr1, and pr2), and in many instances it follows 

paths clearly guided by pre-existing topography (for example, 

the remaining rim of Benzozia Corona and the small shield 

deposits within its interior). Like most of the edifices within 

the quadrangle, Waka Mons as well as the surrounding deposits 
12

are only minimally deformed by tectonically generated features 

such as wrinkle ridges that affect the regional plains. Unlike 

most other edifices, however, Waka Mons is characterized by a 

distinctive set of fractures arrayed radial to the summit, features 

that are inferred to be the surface expression of subsurface dike 

emplacement. These fractures, which extend ~100 km from the 

summit region, both crosscut and are embayed by the lobate 

flow deposits; these characteristics indicate that their emplacement was coeval. A second set of radial fractures, centered 

upon an annular structure southwest of Asintmah Corona, also 

crosscuts and is buried by the Waka/Asintmah unit fe materials. In contrast, this set of radial lineaments, also interpreted 

as a dike swarm, extends more than 1,000 km northeast from 

the focal point. Taken together, these observations indicate that 

the extensive extrusive and intrusive activity within the Waka/

Asintmah complex was interfingered in time, and crosscutting 

and superposition relations clearly demonstrate that the voluminous volcanism characterizing this region was one of the most 

recent events to affect the quadrangle.

Another major edifice within the quadrangle, Xtoh Mons 

(39.7° N., 194.2° E.), is also highly unusual. The main edifice 

sits at the intersection of three topographically elevated regions 

of deformation arrayed in a distinctive Y-shaped pattern, and 

sheeted materials from Xtoh Mons embay these materials (units 

bl and pl) and flow down-gradient into the adjacent lowland 

areas in three locations, where they cover unit pr2 materials and 

are in turn embayed by unit pr3 to the east. The main edifice 

rises roughly 1,000 m above the elevation of the surrounding 

deformation belts, but the mapped unit fe deposits, with a mean 

backscatter of –15.68 dB, are characterized by almost 2,500 

m of relief across the entire area of the volcano, 44 x 103 km2

(~0.7 percent of V–14). Like Waka Mons, Xtoh Mons lies at the 

focus of an extensive system of radiating lineaments inferred to 

be the surface expression of a system of dikes that propagated 

laterally away from the edifice. The lineaments crosscut units 

fe, bl, pl, and pr2 units across distances of as much as 400 km, 

but they are generally absent from unit pr3, although faint traces 

of the lineaments can be seen in a few places near the edge of 

unit pr3. We thus infer that extrusive and intrusive activity at 

Xtoh Mons predates unit pr3 and that thinner cover exists in 

those areas that lie at slightly higher elevations, where the partially covered lineaments can still be observed.

Smaller Volcanic Features

In addition to larger edifices, V–14 also contains several 

thousand small shield volcanoes less than 20 km in diameter 

that are sprinkled across the quadrangle. The quantity of small 

shields observed is far fewer than the numbers reported for 

many other plains-dominated regions (see Hansen, 2005); the 

average density of small shields in V–14 is only 0.5 shields per 

thousand square kilometers. The average elevation at which 

shields occur is 50 m above the mean elevation for the quadrangle as a whole, and 95 percent of the shields are distributed 

within ±730 m of this elevation. Individual shield locations, 

however, are not randomly distributed relative to the mapped 

material units, and they often define clusters that ignore material 

unit boundaries. Unsurprisingly there is a high number (~30 

percent) and concentration (1.6 shields per thousand square 

kilometers) of small shields within unit ps, where shieldfed deposits create the material mapped; however, the major 

regional plains units, where 50 percent of the small shields can 

be found, also reveal significant spatial distribution variations. 

Unit pr1 materials, generally older and preserved at higher 

elevations than the other regional plains units, have a concentration of small shield volcanoes that is the same as that of the 

quadrangle overall (namely, 0.5 shields per thousand square 

kilometers). These shields tend to be irregular in planform and 

are spread throughout the different occurrences of pr1 that have 

been mapped. Unit pr2, generally younger than unit pr1 and 

older than unit pr3, has a concentration of slightly less than 

0.4 shields per thousand square kilometers. The majority of 

these small shields tend to be smaller, rounder, and they occur 

near the boundaries of pr2, in close proximity to other higher 

elevation materials on which unit pr2 onlaps; small shields are 

mostly absent from the interior parts of the pr2 units. Clear 

exceptions to this pattern occur, for instance in the southwest 

corner of the quadrangle where a high concentration of shield 

volcanoes is observed on unit pr2 materials, but in general most 

of these small shields are interpreted as kipukas that predate 

emplacement of the pr2 units with which they are associated 

(see Ivanov and Head, 2004). Finally, the concentration of small 

shields in unit pr3 is very low, less than 0.2 shields per thousand square kilometers, and essentially no small shields occur 

within the unit interior. The remaining ~20 percent of small 

shields within the quadrangle generally avoid tesserae and the 

younger unit fe materials, and they are instead concentrated 

almost entirely within the elevated lineated plains regions (unit 

pl) and upon elevated corona rims. Given the number of small 

shields and their geographic distribution, it appears possible 

that (1) concentrations in older units reflect a greater accumulation period for temporally random shield emplacement, (2) 

small shield emplacement occurred predominantly during the 

period predating regional plains emplacement, which suggest 

shields in the plains areas have been buried by the younger 

plains deposits, or (3) some process focuses melting and shield 

emplacement within higher elevation units, perhaps due to the 

presence of thicker crust, or because volcanism taking place at 

lower elevations occurs via different mechanisms (for example, 

plains-forming surface eruptions) than those which occur at 

higher elevations (for example, perhaps magma stalling and 

hence reservoir-derived volcanism predominates; Head and 

Wilson, 1992).

In addition to the limited number of large volcanoes and 

the significantly greater quantities of small shield volcanoes 

described above, there are thirty distinctive, small (diameters of 

less than 20 km) and intermediate (diameters of more than 20 

but less than 100 km) sized edifices clustered in the north-central and southeastern parts of the quadrangle. Ranging from 7 to 

23 km across, these edifices show an array of different topographic, structural, and volcanic characteristics. Over a third of 

the volcanoes (n=11) have a single large caldera, while another 

eight have one or more small pits near their summit. Caldera 

diameters range from 2 to 10 km with a mean between 5 and 

6 km, and caldera-to-edifice diameter ratios range from 0.2 to 

0.6, illustrating that the calderas generally define a significant 
13

part of the edifices with which they are associated. Ten of the 

volcanoes (33 percent) are best classified as steep-sided domes, 

nine of the volcanoes (30 percent) have bulbous or convex-up 

topography (that is, domical), and eight (27 percent) have steep 

conical geometries. Of the remaining three volcanoes, one is 

shield-like, one is best characterized as a volcanic depression, 

and the third has an irregular geometry and may have undergone volcanic spreading (for further description of this volcanic 

spreading, see 47n198FD in Lopez and others, 2008). Twenty of 

the thirty edifices lie within regions mapped as unit pr1 or unit 

pr2 plains; one occurs within a tessera block, one within unit pl, 

one within unit pr3, and the remaining six are associated with 

unit fe materials. Individual edifices both post- and pre-date the 

map units with which they are geographically associated; these 

relations suggest that their formation was at least in part synchronous with their surroundings, and no distinct stratigraphic 

patterns otherwise emerge for the set as a whole.

Coronae

We identify eight coronae—large, often morphologically 

complex volcano-tectonic features characteristically showing a near-circular annulus of structural deformation—within 

the quadrangle. Five of these (Asintmah, Benzozia, Madalait, 

Qakma, and Neyterkob (defined as a multiple corona structure, 

therefore including Cerridwen)) were identified previously by 

Stofan and others (2001) as Type 1 coronae, one (Embla) was 

defined as a Type 2 corona, and three (Benzozia, Cerridwen, and 

Neytercob) were defined as coronae by Crumpler and Aubele 

(2000). In addition, however, there are differences between 

these catalogs and the results of the current mapping effort. 

For instance, the catalog of Stofan and others (2001) lists four 

additional features, each classified as a Type 1 corona, that we 

do not map as coronae. Two of these (30.3° N., 209.7° E.; 28.8° 

N., 209.4° E.) appear to lack key structural (plus volcanic or 

topographic) characteristics of coronae, while for the other pair 

(29.4° N., 195.5° E.; 29.8° N., 191.6° E.) each feature is formed 

by deflections of regional structural trends around elongated 

low-lying areas; in all four instances we were not convinced that 

the observed characteristics require a corona-style formation 

mechanism, although this is certainly one possibility. Crumpler 

and Aubele (2000) classify Asintmah Corona as a large volcano 

instead of separating it from Waka Mons, and they also classify 

Embla, Madalait, Nimba and Qakma as arachnoids. Though 

widely used, the term “arachnoid” is not currently a formal 

classification recognized within the U.S. Geological Survey 

planetary nomenclature scheme, and the dominance of the radial 

patterns (present at only some of these coronae) does not in our 

view warrant their primary classification as an Astrum, a radialpatterned feature.

Asintmah Corona (25.9° N., 208° E.) is a gently elongated 

feature, roughly 170 km north-south by 115 km east-west, 

characterized by a poorly defined annulus of ridges and sub-parallel extensional lineaments. The lineaments generally radiate 

away from Waka Mons on the northern edge of the corona rim, 

whereas a faint set of circumferential lineaments is best seen on 

the southeast part of the corona rim; the southeast part of the 

corona is also where the rim is most readily observed. Heavily modified, the rim is 30–40 km across and, while elevated in 

some locations by as much as 200 m, is generally level with the 

corona interior and surrounding plains. Asintmah Corona does 

not appear to be the source area for any material units currently 

preserved at the surface.

Like Asintmah Corona, Benzozia Corona (27.5° N., 204.5° 

E.) and the Embla Coronae (28.9° N., 205.4° E.) are interpreted as relatively old, relict structures. Neither appears to be 

the source of specific material units, and the coronae interiors 

contain a concentration of small shield volcanoes. Benzozia 

Corona has a diameter of roughly 180 km. The western side 

of the corona is the best preserved, with a rim 30 km across 

rising approximately 500 m above the surrounding plains and 

corona interior. This elevated region exposes unit pl materials, 

with structures that adopt circumferential alignments, that were 

first embayed by unit pr2 plains and then by unit fe materials 

originating at Waka Mons. The fe materials, which breach the 

corona rim on its southeast edge, clearly delineate the presence 

of an internal topographic moat and flow northwestward in two 

narrow circumferential bands as they hug the interior wall of 

the corona rim. The Embla Coronae are a pair of small annular 

structures, together 130 km across from northeast-southwest 

and 80 km from northwest-southeast, that also preserve unit pl

materials on their elevated rims. These materials are embayed 

by unit pr2 to the west and south, by unit fe materials from 

Waka Mons on the north, and by unit pr3 materials on the east 

that also breach the southernmost corona rim and flood its lowlying interior.

Cerridwen Corona (49.6° N., 201.8° E.) and Neyterkob 

Corona (49.7° N., 204.7° E.), each in excess of 200 km across, 

share a rim and thus form a multiple corona system shaped like 

a squashed infinity symbol; the pair is bisected by the boundary with the Pandrosos Dorsa (V–5) quadrangle and hence is 

described as well by Rosenberg and McGill (2001). Unit co

materials occur on the elevated rims of both coronae, and these 

materials are embayed by younger plains deposits. In addition, 

an elongated kipuka of corona flow materials (unit cof) covering 39.5 x 103 km2 to the south of the coronae is interpreted as 

lava flows derived from Neyterkob. Both co and cof materials 

are embayed by unit pr2 plains that fill in low-lying areas and, 

therefore, structural features preserved within unit cof are not 

generally visible for more than a few tens of kilometers into unit 

pr2 or an adjacent patch of unit pr3. The interior of Cerridwen, 

which lies roughly 1 km below the rim elevation and up to a 

few hundred meters above the surrounding plains, also contains numerous small shield volcanoes. The ps unit they create 

occupies the interior floor of the corona. The characteristics of 

the Neyterkob Corona interior are quite similar; unit ps materials lie roughly 1.2 km below the adjacent rim, and they occur at 

roughly the same elevation as the immediately adjacent plains 

to the south and east.

Madalait Corona (37.6° N., 206.4° E.), 160 km northwestsoutheast by 120 km northeast-southwest, is part of a northwesttrending chain of structures of probable volcanic origin. The 

corona is characterized by an elevated rim (~800 m above the 

surrounding plains) and low-lying interior (~200 m below 

the surrounding plains). The interior has a high concentration 

of small shield volcanoes. Formation of the rim appears to 
14

have displaced unit pr2 materials, which indicates the corona 

formed after the local unit pr2 deposits were emplaced. The 

rim is embayed by unit pr3 and unit fe materials on three sides, 

and the overlapping deposits from the shield volcanoes in 

the corona’s interior form unit ps materials that also postdate 

formation of the rim. Nimba Corona (32.8° N., 204.5° E.), 90 

km in diameter with a structurally defined annulus of extensional fractures, deflects and thus postdates the regional unit pr1

materials within which it is located. The interior of the corona 

is fairly flat, slopes gently down to the southeast, but is elevated 

up to a kilometer above the surrounding plains. Unit cof materials, also interpreted as lava flows associated with the corona, 

are superimposed as faint lobate deposits directed downslope 

on unit pr1 and cover a net area of roughly 19 x 103 km2; these 

same unit cof deposits are in contact with units ps and pr2

but the stratigraphic relations with these units are less certain. 

A pattern of pseudo-radial ridges is observed within units cof

and pr1, visible most clearly on the north and west sides of the 

corona; these features are not observed to cross into units pr2 or 

ps.

Qakma Corona (35.5° N., 207.1° E.), like Nimba Corona, 

is a small circular feature (120 km across) with an annulus characterized by circumferential extensional lineaments that serves 

as the locus for a system of radially aligned ridges. The rim, 

elevated at most by a few hundred meters above the surrounding plains, preserves unit pl materials, but nearly all other traces 

of the corona structure have been buried beneath the unit pr2

and unit pr3 materials that characterize the region. Similarly, 

the interior of the corona—which unlike Nimba is a depression extending almost 1 km below the surrounding plains—has 

been obscured by younger deposits, in this case unit fe materials (derived from the Kokyanwuti Mons edifice in the Bellona 

Fossae (V–15) quadrangle) that flow westward downslope 

across units pr1, pr2, and pr3 before ponding in the low-lying 

corona interior.

Impact Craters

The V–14 quadrangle contains eleven impact craters, 

one feature which might be a twelfth impact crater (~32.2° N., 

195° E.), and four airburst features (also called splotch craters); 

these airburst features do not create material units, but they 

distinctively modify the local material(s) with which they are 

geographically associated. Together they cover approximately 

31 x 103 km2 (0.5 percent of V–14), and yield an average crater 

density (ignoring the tentatively identified crater) of 2.3 craters 

per million square kilometers (without airburst features, 1.69 

craters per million square kilometers). This is greater than the 

global average of essentially 2.0 craters per million square kilometers (see Ivanov and Basilevsky, 1993; Namiki and Solomon, 

1994; Price and Suppe, 1994; Strom and others, 1994), but the 

difficulties inherent to efforts striving to extract dating information from these data are well documented (see Campbell, 1999). 

Many of the craters in the quadrangle, however, are associated 

with “haloes” of dark material that are often parabolic when 

the deposits are laterally extensive; these are indicated by a 

fine stippled pattern on the map. Thought to represent airfall 

deposits, dark halo materials are probably loosely consolidated 

and likely subject to weathering and erosion over time; where 

haloes have yet to be obliterated by weathering processes, it 

has been argued that deposits from the crater must be from <10 

percent (parabolic) to ~70 percent (faint dark) of the mean planetary surface age (see Arvidson and others, 1992; Campbell and 

others, 1992; Basilevsky, 1993; Basilevsky and others, 2003). 

If this hypothesis is correct, then eight of the eleven craters, and 

presumably all of the airburst features, formed during the past 

few tens to hundreds of millions of years.

The craters associated with dark-halo deposits include, in 

order of increasing crater diameter: Lisa (D = 4.5 km; 29° N., 

182° E.), Yambika (D = 6.5 km; 32.6° N., 208.7° E.), Unitkak 

(D = 8 km; 40.8° N., 199.5° E.), Olivia (D = 10.2 km; 37.2° N., 

207.9° E.), Ugne (D = 10.3 km; 34.9° N., 205.8° E.), Uleken 

(D = 10.9 km; 33.7° N., 185.1° E.), Akiko (D = 17.4 km; 30.6° 

N., 187.3° E.), and Yablochkina (D = 64.3 km; 48.3° N., 195.3° 

E.). Lisa, superimposed on unit pr2, is surrounded by ejecta 

deposits that extend up to 11 km from the rim and a small dark 

halo, with a fairly equant geometry, that extends ~45 km west 

from the crater center. Yambika, superimposed on unit pr1, is 

surrounded by ejecta out to roughly 11 km and by a faint dark 

halo visible in all directions to distances of roughly 25 to 35 

km from the center of the crater. In sharp contrast to Yambika, 

Unitkak is superimposed on unit pr2 and has a NNW–SSEaligned butterfly-shaped ejecta pattern that extends up to 18 

km from the crater rim. This crater is also marked by a highly 

unusual “tail” of dark-halo materials only a few kilometers wide 

but extending ~600 kilometers to the west-southwest. The “tail” 

is clearly visible on units pr2, pr3, fe, and pl, and we tentatively interpret this tail, in combination with the butterfly ejecta 

pattern, as evidence that the impacting body passed extremely 

close to the surface. Specifically, the passing body approached 

its target at a very low impact angle, in the recent geologic past. 

Olivia, which impacted unit pr3, is surrounded by an ejecta 

blanket out to distances of 23 km, but it shows only a faint dark 

halo deposit. The main region of the halo is egg-shaped, 170 km 

east-west by 70 km north-south, covers unit pr3 and pr2 materials, and like Unitkak there is also a “tail” of sorts that extends 

another 130 km to the west. This might also suggest a low-angle 

passage, but the absence of butterfly ejecta, the faintness of the 

dark regions, and the presence of the larger halo deposit near the 

crater all argue against this interpretation. We infer instead that 

Olivia is among the oldest dark halo craters in the quadrangle, 

and that the observed features are weathered remnants of what 

used to be a more extensive dark halo deposit. Ugne, which 

impacted unit pr2 materials, is also surrounded by a faint halo, 

in this case equant and extending 75 to 85 km in all directions. 

The butterfly-shaped ejecta pattern extending 20 km from the 

crater rim also suggests the possibility of a low-angle impact 

(in this case coming in from the north, a less common trajectory), and the ejecta appears to cover lineaments and wrinkle 

ridges associated with Qakma Corona; along the western edge, 

the ejecta also appears to have abutted against pre-existing 

wrinkle ridge topography, implying the possibility that fluidized ejecta emplacement occurred to a limited extent. Uleken, 

like Ugne, is associated with a faint dark halo of limited extent 

(~140 km across), but for this crater the presence of fluidized 

ejecta emplacement is clear, and it defines a set of sinuous flows 
15

that traverse more than 30 km across the unit pr2 materials into 

which the impact occurred. The faint nature and limited extent 

of the haloes preserved at both Ugne and Uleken suggest that 

these impacts, along with Olivia, are among the oldest dark halo 

craters within the quadrangle. Conversely, the remaining two 

craters—Akiko and Yablochkina—have extensive dark halo 

deposits and are inferred to be, along with Unitkak, some of 

the youngest impact craters in the quadrangle. Akiko impacted 

into Lahevhev Tesserae, and while the ejecta deposits cover the 

structural deformation that has occurred near the impact out to 

distances of about 10 km the ejecta deposits, in turn, appear to 

be embayed or buried by intratessera plains and similar deposits 

within the adjacent unit pLl materials. The dark-halo deposits, 

parabolic in geometry, cover a variety of units (units t, pLh, pLl, 

pl, pr3, pr1, pr2, and crater Lisa) and extend out to a distance of 

at least 600 km west of the crater center; however, they become 

fainter with increasing distance, and the deposit could extend 

farther because the greatest lateral extent shown in our mapping 

was defined conservatively. Similar criteria were used to define 

the parabolic dark halo deposit surrounding crater Yablochkina, which extends at least 1,270 km east-west (850 km west 

of the crater center) and 700 km north-south; the north-south 

distance is clearly a minimum as the parabola extends well 

into the adjacent V–5 quadrangle to the north. The dark-halo 

deposit covers a variety of material units (units t, pr2, co, cof, 

pr3, pl, bl, ps, ph, and fe), and unit boundaries are often more 

difficult to define throughout the 15 percent of the quadrangle 

that is affected. Crater Yablochkina is the only example in the 

quadrangle large enough to have formed a double-rim structure. 

The inner rim, 48 km across, is surrounded by an outer rim 

measuring 64.3 km in diameter that can be observed clearly 

only on the north, west, and south sides of the crater. The crater 

is surrounded by large ejecta blocks and fluidized deposits 

out to distances of 50 km from the outer rim, and these radarbright deposits are, in turn, completely surrounded by a very 

low backscatter (–20.52 dB, the lowest in the quadrangle), 

extremely smooth deposit (RMS slope of 1.2°, lower than 98 

percent of V–14’s surface overall) with sharp boundaries that 

is distinctly separate from the dark-halo deposits; this material 

is mapped as unit cf. The spatial association between unit cf

and the radar-bright Yablochkina ejecta suggests a link between 

the two. The unit has no other unusual physical properties (for 

example, emissivity), does not conform to topography, and we 

interpret this material as fine fraction flow deposits associated 

with Yablochkina’s formation (see figure 32 in Schultz, 1992).

The three impact craters in the V–14 quadrangle that lack 

dark-halo deposits include, in order of increasing diameter: 

Clementina (D = 4 km; 35.9° N., 208.6° E.); Raymonde (D = 

5.3 km; 48.4° N., 195.3° E.); and, Nadira (D = 31.4 km; 44.1° 

N., 201.5° E.). The absence of a dark halo deposit suggests 

that emplacement of each crater occurred long enough ago that 

weathering has had time to remove the halo deposit; we infer 

from the presence of haloes around small craters like Lisa that 

even the smallest craters likely formed a halo deposit initially. 

It seems likely, however, that small craters deposit less extensive and perhaps thinner dark halo deposits than large craters. 

If small craters do indeed have less extensive and thinner dark 

halo deposits, it follows that the time required to eliminate the 

haloes via weathering may be far less than the 10 to 70 percent 

inferred from study of major parabolic deposits. Clementina, 

slightly smaller than Lisa, impacted into unit fe materials 

inferred to originate from Kokyanwuti Mons in the V–15 quadrangle. The crater has a highly asymmetric ejecta deposit that 

extends only 1 to 2 km in most directions but up to 21 km to the 

south. Raymonde, which impacted into unit pr2, is very similar, 

with asymmetric deposits that extend as much as 20 km from 

the crater rim. In contrast, Nadira is a large complex crater with 

a central peak, surrounded by ejecta that extend 15 km or so in 

all directions. The crater lies within a slightly elevated patch of 

unit pr2, and it is possible that the northeast edge of the ejecta 

blanket, where it lies at the lowest elevation, has been covered 

by the unit pr3 materials that surround the unit pr2 materials. If this interpretation is correct, it implies that the impact 

postdates unit pr2 and predates unit pr3. The coincidence of 

the darker materials with a spur of higher elevation, the fairly 

high emissivity for the deposit (dark haloes normally have a low 

emissivity), and the similarity between the dark materials and 

nearby sections of unit pr2 plains supports this map interpretation. An alternative and defensible interpretation, however, is 

that the materials mapped as unit pr2 are misidentified and are 

in fact the final remnants of a dark halo deposit; this alternative 

interpretation would mean that Nadira impacted into unit pr3

materials.

The final class of impact-related features present within the 

quadrangle is characterized by distinctively blotchy, diffuseappearing surface modification inferred to originate when 

an incoming bolide fails to penetrate completely through the 

atmosphere, instead exploding in close proximity to, and thus 

disturbing, the surface without creating a crater (Schultz, 1992). 

The smallest, and also the least clear example of these so-called 

“splotch” craters (airburst features), is an irregular blotchy 

deposit 28 km across. It modifies unit pr3 and is distinctly different than any materials nearby, and it is tentatively identified 

as an airburst product based on both its general appearance and 

the fine-scale flow features aligned radial to the center. The next 

largest splotch crater, 40 km in diameter, modifies units pr1

and pr2, and it is characterized by a brighter core and surrounding darker material (see figure 8c of Schultz, 1992). The third 

“splotch” crater, 52 km in diameter, modifies unit pr2 materials, is circular, and contains a radar-bright pitted surface at the 

center. The final example, which also modifies unit pr2 materials, is 75 km across and has a small dark center surrounded by a 

brighter, rougher halo of material. The sequence of unit cf materials, increasing in size, indicates variations in the efficiency 

with which the bolide’s energy couples to the atmosphere; in 

other words, the greater blast areas and small dark interiors 

gradually transition to small, darker features with radar-bright 

pitted surfaces commonly observed at the core (Schultz, 1992).

Structural Deformation

The high degree of structural deformation preserved within 

the oldest units of the V–14 quadrangle (for example, tesserae 

and deformation belts) demonstrates either that these units are 

much more susceptible to deformation than their surroundings, 
16

or that the early stages of the quadrangle’s history involved 

amounts of net strain accumulation that were far greater than 

the deformation accommodated subsequently within the surrounding plains materials. Observed superposition and crosscutting relations at the margins of the oldest units best support 

the latter interpretation but, due to the limited coverage of the 

old deformed areas that remain exposed, it is not possible to 

assess the original extent or pervasiveness of these earliest 

stages of deformation. Descriptions of the deformation patterns 

preserved within tesserae and deformation belts are provided 

herein; here we focus on structural deformation within the 

remaining material units, limiting analysis to mapped features 

greater than 30 km in length. We also provide a brief structural 

characterization of Fornax Rupes (defined by a high concentration of wrinkle ridges), Ganis Chasma (lineaments, graben, and 

troughs), Ahsonnutli Dorsa (lineaments and ridges) and Akawa 

Dorsa (lineaments and troughs), the only concentrations of 

deformation other than tesserae warranting a name within the 

quadrangle.

Contractional Deformation

Contractional deformation, in the form of wrinkle ridges 

(see McGill, 1993) and a handful of larger, arch-shaped ridges, 

occurs throughout the quadrangle. The 52 arch-shaped ridges 

represent a minor form of contractional deformation and never 

exceed 100 km in length. They have two distinctive characteristics: they are all generally aligned close to a north-south 

direction, and all but a handful (for example, in Ahsonnutli 

Dorsa) occur at the margins of elevated, highly deformed 

materials (for example, units bl and pl). Though these ridges 

are several kilometers wide, the topography of the features can 

be hard to detect, and the preferential north-south alignment 

may thus simply reflect a bias against observing linear features 

aligned with the approximately east-west radar look direction. 

In contrast to the arch-shaped ridges the wrinkle ridges in V–14, 

typically a few hundred meters across, represent a major form 

of contractional deformation within the quadrangle, and have 

a net length of 58,600 kilometers. Almost 80 percent of this 

net length occurs within regional plains units pr2 (47 percent; 

these plains occupy 40.4 percent of V–14), pr3 (17 percent; 9.3 

percent of V–14), and pr1 (15 percent; 13.1 percent of V–14); 

all three units contain higher than expected length percentages 

when compared to the percentage area they cover within the 

quadrangle. Their mean elevation (length-weighted; the net 

length for each lineament is divided into the sum of the raster 

cell elevation times the raster cell size for each lineamentcrossed topography pixel) is 100 meters below that of the quadrangle as a whole, reflecting their preferential formation within 

the major plains units.

A cumulative length plot (fig. 3) illustrates that both the 

absolute and net lengths of contractional lineaments are about 

half that of the comparable figures for extensional structures 

within the V–14 quadrangle. No quadrangle-wide pattern of 

contractional deformation is observed, but regional and local 

patterns of alignment are evident; these patterns indicate that 

the most recent episodes of strain have been accommodated in 

different ways in different areas (Venechuk and others, 2005). 

In the northwest quadrant, for example, nearly all wrinkle ridges 

align in an east-west orientation that mirrors and contributes 

to the deformation that defines Akawa Dorsa. In contrast, the 

dense network of wrinkle ridges within the northeast quadrant, most notably expressed within unit pr3 materials, has a 

northwest-southeast alignment that has no obvious relation to 

the topographic or other gross characteristics of the area; an 

exception to this occurs locally where wrinkle ridges lie immediately adjacent and parallel to the double-annulus defining the 

Cerridwen and Neyterkob Coronae, structures similar in scale 

to Akawa Dorsa. When wrinkle ridges throughout the quadrangle are summed into 15° bins (that is, alignments from N to 

N. 15° E., from N. 15° E. to N. 30° E.), only 5 to 12 percent of 

the population is aligned in each (Venechuk and others, 2005); 

this finding demonstrates the overall failure of the population to 

adopt one or more preferred orientations at the quadrangle scale.

Extensional Deformation

Extensional deformation within V–14 shows a greater 

variety of structural styles than is observed for contractional 

deformation. Minor extensional features include true graben 

(fault-bounded, flat-floored depressions) and troughs (wide, 

deep, elongated depressions without clear evidence of bounding 

faults). The 48 graben, with individual lengths as much as ~150 

km and a net length of 3.3 thousand kilometers, are principally 

located within unit pG, with isolated occurrences at other locations. Their mean elevation is 300 m above that of the overall 

quadrangle, a fact that reflects a strong association with Ganis 

Chasma. Formal labeling of a feature as a graben was applied 

conservatively by requiring clear detection of the flat floor 

and faulted walls; it is possible that many features labeled as 

extensional lineaments could be graben as well, but their narrow 

widths prevent further characterization at the available radar 

image resolution. The 22 troughs identified also reach lengths 

just in excess of 150 km, but they have a net length significantly 

less than that of the graben (1.4 thousand kilometers). Like the 

graben, many troughs are observed within unit pG, but the rest 

are concentrated within Fornax Rupes, which leads us to infer 

their extensional origin.

Narrower structures defined here as lineaments are much 

more numerous (n=1,222) and are inferred to be extensional 

from their fairly uniform width and linearity across considerable distances. They are distributed in a non-uniform fashion 

throughout the quadrangle and extend for a net length of 71.8 

thousand kilometers. Only 53 percent of this length occurs in 

regional plains units pr2 (35 percent; 40.4 percent of V–14), 

pr1 (16 percent; 13.1 percent of V–14), and pr3 (2 percent; 9.3 

percent of V–14), and hence the lineaments are underrepresented in these areas relative to the part of the quadrangle the 

units cover. Lineaments also tend to be noticeably absent from 

areas where abundant wrinkle ridges have formed (see unit pr2

in northwest quadrant; unit pr3 in northeast quadrant; and, in 

the units within the south-central portion of V–14), but in other 

areas they define concentrated patterns that clearly reflect both 

local and regional stress fields. For example, from 35–40° N. 

and 180–195° E., an organized system of lineaments runs eastwest along the elevated belts of unit pl that characterize this 
17

area, parallel to the wrinkle ridges in the immediately adjacent 

plains materials. Similarly, regional-scale patterns are observed 

defining Ganis Chasma (northwest-southeast aligned) and 

Fornax Rupes (northeast-southwest aligned), and lineament sets 

in the northeast corner of the quadrangle are aligned both parallel and perpendicular to the Neytercob and Cerridwen Coronae 

across distances of up to 500 km; the major perpendicular set, 

running northeast-southwest, creates the dominant structural 

character of Ahsonnutli Dorsa. Lineaments also define the 

circumferential deformation characterizing many other coronae 

and annular structures, the majority of which lie along the trace 

of Fornax Rupes. When lineaments throughout the quadrangle 

are summed into 15° bins, only 5 to 15 percent of the population is aligned in each (Venechuk and others, 2005). As was the 

case for the wrinkle ridges, this finding demonstrates that the 

lineaments population does not adopt a preferred orientation at 

the quadrangle scale.

The final set of extensional structures includes two sets 

of lineaments that radiate away from a central volcanic edifice 

or structure; we interpret these features as the surface expression of subsurface dikes propagating laterally at shallow depth 

using criteria defined by Grosfils and Head (1994a,b), but the 

lineaments radial to Cerridwen and Neyterkob Coronae are 

not included in this designation as it is not obvious that these 

features need be dike-underlain. The first set, consisting of 118 

structures each greater than 30 km in length, radiates some 400 

km across roughly 270° of arc from Xtoh Mons. The second set 

includes 119 structures within V–14 that radiate in total more 

than 1,000 km (conservatively) from Waka Mons and a volcanic center just to the southwest (Grosfils and Ernst, 2002), with 

some structures extending significant distances northeast into 

the adjacent V–15 quadrangle. These lineaments run parallel to 

Fornax Rupes and eventually merge with the structures defining Bellona Fossae, the feature from which V–15 derives its 

name, and thus this subset of northeast-striking radial features 

likely formed within the same stress regime (possibly at the 

same time as?) Bellona Fossae and Fornax Rupes. Since these 

radial lineaments are buried by Waka Mons deposits, which in 

turn are cut by other radial features from the same center that 

do not curve into a northeast alignment, it would appear that 

major (quadrangle-scale) stress patterns can be changed and/

or eliminated in geologic intervals that are commensurate with 

the lifetime and activity at a single volcanic center. While such 

times are currently unconstrained for Venus volcanic centers, if 

these focused areas of magmatism are akin to those on Earth—

a connection suggested by both the observed morphologies 

and the pulsed nature of the activity—then the period of time 

implied is likely to be on the order of a few million to at most 

a few tens of millions of years (see Bryan and Ernst, 2008, and 

references therein).

Geologic History

It is challenging to organize the stratigraphy within the 

quadrangle into a single comprehensive sequence due to the 

presence and extent of (1) the morphologically, temporally 

diverse “garbage bag” plains unit pr1 that cuts several broad 

swaths across the quadrangle, and (2) a few extensive, craterrelated, radar-dark deposits—most notably from the crater 

Yablochkina—which obscure stratigraphic details within 

parts of the quadrangle. Several clear regional sequences can 

be defined, however, and each stratigraphic sub-region is 

characterized by a common sequence of transitions from one 

predominant style of geological activity to another. This could 

indicate that each local region records a similar sequence of 

transitions occurring at different times and/or rates, or that 

some (perhaps all) local regions endured a general sequence 

of geologic events at about the same time and rate. In the next 

few sections and in the Sequence of Map Units (see map), we 

present the general stratigraphic sequence of units and events 

in the quadrangle.

Precursor

Tessera terrain t is consistently the oldest unit where it is 

observed as part of a local stratigraphic sequence, and the same 

is true for deformation belt unit bl. The relative timing of these 

two units is unconstrained based on the observed stratigraphy. 

Deformation belts are the simplest, preserved as linear elevated 

regions of heavily deformed material characterized by early 

contractional deformation and later stage extensional deformation. Tessera terrain, like deformation belts, is embayed or 

crosscut by all surrounding units, but its structural record has 

obliterated the signature of all precursor material. In no location 

do we observe tesserae forming at the expense of other units, 

though some deformation affecting tessera blocks also affects 

the surrounding materials. Tesserae within specific regions 

tend to contain similar deformation patterns (for example, the 

disparate blocks of Nemesis Tesserae preserve internally similar 

deformation), but tesserae materials from location to location 

within the quadrangle do not (for example, Nemesis Tesserae 

and Lahevhev Tesserae preserve different structural histories 

and stress alignments).

Period 1

A complex era of intermingled plains emplacement and 

distributed deformation dominated for some interval following tesserae and deformation belt formation. This era yielded 

two distinct types of units that locally are older than everything 

but the precursor materials; however, they do not occur in a 

consistent sequence relative to one another and instead show 

variable temporal relations in different areas of the quadrangle. 

The first type of unit consists of different plains materials cut by 

pervasive extensional deformation (namely, units pG, pl, pLh, 

and pLl) and preserved as elevated kipukas. The original extent 

of these units is not clearly understood because they are mostly 

covered by younger deposits and no source regions are apparent. The second unit type, unit pr1 material, is at least locally 

the oldest feature other than tesserae and deformation belts. 

These plains again preserve no clear source regions and have, 

relative to other plains units in the quadrangle, an intermediate 

radar backscatter and a highly blotchy appearance suggesting 

they may be defined by the amalgamation of many localized 

(perhaps fissure) eruptions. Consistent with this, they also show 

high concentrations of extensional deformation relative to other 
18

regional plains units but a fairly low concentration of contractional structures. Unit pr1 materials display stratigraphically 

variable contact relationships that are often ambiguous locally 

but, viewed collectively, indicate the unit has undergone a prolonged history of spatially and temporally patchy emplacement 

and modification.

The formation of coronae in V–14, and formation of 

material units co and cof, also occurred predominantly during 

this period, although limited corona-forming activity extends 

into Period 2. Lineated plains units and unit pr1 commonly are 

found draped upon the elevated rims that have been preserved, 

which indicates that these materials were emplaced prior to 

development of the rim topography. The rim topography was 

then embayed by unit pr2 and younger deposits. While the process of corona formation and topographic development can take 

considerable time (Smrekar and Stofan, 1997), the observed 

stratigraphic details suggest that coronae are among the oldest 

volcanic center signatures preserved within the quadrangle. 

Only one corona, Madalait, has unit pr2 plains materials on its 

rim, and this single example appears to be distinctly younger 

than the other coronae in the quadrangle.

Period 2

The next interval is characterized predominantly by extensive plains volcanism, unit pr2; this unit preserves a similar 

degree of contractional deformation and a significantly lesser 

degree of extensional concentration than the older unit pr1

plains materials. The unit pr2 plains have a lower backscatter than other regional plains units, and embayment of other 

material units as well as the superposition locally on different 

lineament sets both suggest a fairly thin, possibly low viscosity 

deposit. Emplacement of this unit appears to have occurred over 

a prolonged interval and, though younger than unit pr1 in most 

places, in a few places the two units are clearly overlapping. In 

addition to coinciding with the formation of Madalait Corona, 

this period is also characterized volcanicly by the formation of 

Baltis Vallis, which cuts unit pr2 and is infilled locally by unit 

pr3, as well as a transition from coronae to large edifice formation and initial emplacement of unit fe materials.

Period 3

The final distinct phase, which extends until the present, is characterized predominantly by edifice-related volcanism, which has formed unit fe, and emplacement of a third 

regional plains material, unit pr3. Unit pr3 is characterized by 

an intermediate and more uniform radar backscatter than the 

other plains in the quadrangle. Most of unit pr3 occurs as a 

single continuous and spatially extensive unit with no evident 

source; onlap relations reveal this unit is thicker in the middle 

and thin at the edges, and unlike the older unit pr1 and unit pr2

plains, this broad patch appears to define a stratigraphically 

brief (possibly continuous?) emplacement event. Other small 

patches of unit pr3 are similar in stratigraphic position, and 

collectively they preserve a significantly higher concentration 

of contractional deformation and a significantly lesser degree 

of extensional deformation than the older unit pr1 and unit pr2

materials. Complementing the unit pr3 plains, several large 

(>100 km diameter) volcanoes formed and the lobate unit fe

materials from these constructs are generally superimposed on 

the surrounding materials, including unit pr3. Similarly, the 

single instance of unit ph, identified as a possible pyroclastic 

deposit, is younger than the units with which it comes into contact. Uncertainty remains concerning the source region for this 

unit, but unit ph lies at the base of a large (~900 km diameter), 

unnamed domical uplift. If this uplift and the other young volcanism it exhibits (abundant unit ps materials and a fanning lineament system, which may be dike-underlain) are plume related, 

it could indicate that one of the final major pulses of volcanic 

activity in the quadrangle involved volatile-rich magmas. 

Finally, several extensive unit ps plains characterized by overlapping small shield deposits are associated with period 3. The 

duration of time over which the small shields were emplaced is 

almost by definition unconstrained within the interior, but like 

unit fe, the ps units are almost everywhere younger than the 

materials against which they abut; the only exceptions to this 

are two instances of contact with unit fe and the interaction with 

unit ph. With clear evidence for earlier phases of small shield 

formation, it appears that the formation of diminutive edifices 

has occurred during several major stages, or perhaps persistently, throughout the quadrangle’s preserved history.

Cratering

On the basis of superposition relations observed for the 

impact craters and their ejecta, all but one crater (Yambika) 

formed during or subsequent to period 2, the era of unit pr2

plains emplacement, and nearly half of the craters formed in 

period 3 during or after the emplacement of unit pr3. Only one 

crater, Nadira, has been embayed since it formed, hence placing 

an upper bound on its time of formation. The remainder must be 

younger than the units into which they impacted and onto which 

their dark halo deposits and ejecta were deposited, but no further constraint based on superposition is possible. As discussed 

previously, however, most craters in the quadrangle preserve 

dark halo deposits to some degree (italicized craters shown on 

the Sequence of Map Units are the exceptions to this); the lack 

of dark halo deposits suggest that these craters may have formed 

within the last few tens to hundreds of millions of years.

Discussion

Mapping within the V–14 quadrangle, as noted in the 

Introduction, was performed to yield insight into four specific 

questions.

Question 1: Has the dominant style of volcanic expression within the quadrangle varied in a systematic 

fashion over time?

There is a clearly preserved variation in volcanic style 

within the V–14 quadrangle, and it suggests a processional volcanic sequence. We also hypothesize that the precursor materi-
19

als from which tesserae and deformation belt units have formed 

were volcanic as well, but there are no mapping constraints 

suitable at present for testing this hypothesis.

Stratigraphically early plains formation and the emplacement of small shields dominate the bulk of the stratigraphy 

exposed; evidence for the latter is now largely preserved 

adjacent to and upon kipukas within the most elevated regional 

plains units. The oldest units are generally the most heavily 

deformed, and in many places they were uplifted during coronaforming processes that prevented the units’ subsequent burial 

when younger plains materials were erupted onto the surface. 

The interplay between structural and material unit elements preserved at some coronae make it clear that activity at these magmatic centers continued over a prolonged period. The coronae 

characteristics observed within V–14 are consistent with their 

genesis during delamination events affecting a thin lithosphere 

(Smrekar and Stofan, 1997), but the observed morphologies and 

ages do not support other proposed models of corona formation 

(see DeLaughter and Jurdy, 1999).

In the later stages of the quadrangle’s evolution, small 

shield emplacement continued to form the mapped units of ps, 

but the style of volcanism otherwise largely appears to have 

localized into edifice formation at distinct centers of activity; 

the gradual but clear transition from corona- to large edificedominated construction at volcanic centers is consistent with 

predictions involving gradual lithospheric thickening over time 

(see McGovern and Solomon, 1998). The duration of activity 

at individual large edifices is poorly constrained, but it is clear 

that the latest activity at essentially all of the large volcanoes, 

based on superposition and crosscutting relations of materials 

mapped as unit fe with their surroundings, postdates the most 

recent activity in adjacent units. Interestingly, in addition to the 

geologically recent effusive growth at large edifices, the characteristics of unit ph indicate that late-stage activity in at least one 

area of the quadrangle, adjacent to a large, unnamed domical 

volcanic rise 900 km across, may have involved explosive eruption of magmas with an extremely high volatile content.

In addition to effusive and possibly explosive activity, 

careful evaluation of the volcanic, tectonic and topographic 

evolution of two extensive, edifice-centered radial fracture systems using techniques defined previously (Grosfils and Head, 

1994a,b) provides insight into a third major style of late-stage 

volcanic activity within V–14: subsurface emplacement of giant 

radiating dike systems. The dikes in each radial system are 

inferred, from the combination of observations, to have injected 

laterally away from a shallow magma source. Calculations 

indicate that the magma reservoirs associated with each source 

were likely to be a few tens of kilometers in plan-view radius, 

and that the dikes fed from these reservoirs would need to be a 

few tens of meters across (Grosfils and Ernst, 2002). The rapidity with which individual dikes are emplaced (days to a week or 

two for dikes ~1,000 km long given thermal- and fluid-dynamic 

limitations on dike growth; Ernst and others, 1995) make these 

features excellent stratigraphic tie points. The interplay between 

the dike-induced lineaments seen at the surface and the material 

units with which they interact indicates that thermal and hence 

volcanic activity at both centers reoccurred during several distinct episodes over a stratigraphically prolonged interval.

Question 2: Does the tectonic deformation within the 

quadrangle record significant regional patterns that 

vary spatially or temporally, and if so what are the 

scales, orientations, and sources of the stress fields 

driving this deformation?

Analysis of the structural styles preserved within the 

quadrangle indicates that significant and fairly systematic 

changes have occurred as a function of time (see Sequence of 

Map Units). The earliest phases of structural deformation in 

the quadrangle (for example, those forming units t and bl) are 

predominantly contractional. Following this interval, the oldest 

plains units preserved are characterized by significant degrees 

of extensional deformation but only limited contraction; correlation between the development of early stages of volcanism 

and a period of enhanced extension may not be accidental. As 

volcanic activity within the quadrangle continued, however, it 

gradually led to the emplacement of the major regional plains, 

and contractional deformation once again came to dominate 

the structural signatures observed; this interval of variation 

corresponds to the gradual shift from regional plains emplacement to localized centers of activity. Finally, the nature of the 

most recent stress fields in the area is generally unconstrained 

because the stratigraphically youngest units preserve only limited amounts of structural deformation.

Spatial analysis of tectonic deformation within V–14 as 

a whole does not reveal a quadrangle-wide pattern of spatial 

deformation but rather discrete zones, roughly one fifth to 

one-fourth the area of the quadrangle in size, that have distinctive tectonic patterns. Quantitative analysis of the lineaments in 

these zones in some cases reveals clear evidence of structural 

organization across wide areas. For instance, within a zone 

stretching across the northern part of the quadrangle (~2 x 1012

km2), suites of extensional and contractional lineaments show 

clear orthogonality (Venechuk and others, 2005). This characteristic may indicate that the tectonic deformation occurred 

during a geologically brief interval, or it could indicate that the 

structures formed in the presence of a long-lived, persistently 

aligned regional stress field. A similarly orthogonal pattern 

(requiring regional stress fields aligned in a very different 

direction from the northern area) occurs in the southwest part of 

V–14. In other areas of the quadrangle, in contrast, extensional 

and contractional lineaments are aligned sub-parallel to each 

other or lack coherent geometric organization; these observations indicate variability in stress field alignment over time 

and/or possible reactivation of individual structural elements. 

Reactivation has been observed in other regions (see DeShon 

and Hansen, 2000).

Stratigraphically, combining the temporal and spatial characteristics, there is a general sequence preserved in which the 

oldest units show the most deformation and the youngest units 

the least; however, specific units fall outside these patterns, 

which suggests deformation concentration has occurred at some 

level. There are several possible interpretations of these data. 

The most obvious one is that enhanced extensional deformation occurred across the region during the interval of emplacement represented by the units coeval with and predating plains 

unit pr1, with lesser degrees of extension thereafter; enhanced 
20

levels of contractional deformation within late-stage plains 

units largely appear to reflect accommodation of pre-existing 

topography. Another possibility, but one we consider less viable 

on the basis of the map data, is that the process of deformation 

took place after emplacement of most material units, with little 

deformation occurring in some materials and hence preferential concentration of structural features within what are now 

the most heavily deformed plains units. These more deformed 

areas remain the stratigraphically oldest, which would suggest 

that some factor, perhaps related to their pre-existing stress or 

thermal state, their material properties, or their thickness is fundamentally different than the properties of the younger plainsforming materials.

The current mapping effort does not concentrate heavily 

upon the structural deformation recorded within tesserae, but 

the structural data and geologic history preserved within these 

units yield insight into early- and late-stage deformation within 

the quadrangle, and each area has its own particular geologic 

character. Nemesis Tesserae form an elongate belt that cuts 

east-west across the north-central part of the quadrangle. It 

is preserved as elevated kipukas that have been embayed by 

surrounding plains units, and there is no progression of deformation observed; for example, structures that systematically 

deform both the tessera blocks and parts of the surrounding 

plains are absent. Deformation within this tessera terrain was 

essentially complete by the time the surrounding plains and 

topography were emplaced. In contrast, the Athena Tesserae 

occur as an equant block (contained mostly within V–13 to 

the west) that exhibits interplay between tectonic deformation, 

plains emplacement, and uplift. For example, along the eastern edge of the quadrangle (31.5° N., 182° E.), the tessera was 

embayed by plains deposits, then both the plains and tessera 

apparently underwent an episode of structural deformation 

perpendicular to the embayment boundary that cut across them 

both to form unit pl. The contact between the two material units 

was subsequently uplifted, and a second plains emplacement 

event, which formed unit pr1, embayed both the structural lineaments and the older plains unit where they occurred at lower 

elevations. Following continued uplift, emplacement of unit 

pr2 materials in the lowest lying areas occurred. This event is 

an example where late-stage tectonic deformation of the tessera was coeval with early regional plains emplacement, while 

later plains emplacement events occurred during an interval of 

ongoing topographic adjustment. Finally, the Lahevhev Tesserae appear to be the remnants of a larger coherent block of 

tessera which is in (or ceased deforming during) the process of 

being torn apart by tectonic and volcanic activity. The inferred 

block is cut in several places by rift-like topography within 

which flooding and subsequent development of lineaments with 

a braided and/or feathery geometry has occurred, potentially 

indicative of local shearing. The larger coherent blocks of tessera preserved within Lahevhev Tesserae resemble Nemesis 

Tesserae in that their internal deformation is clearly not coeval 

with emplacement of the surrounding plains.

Given the changes in tectonic deformation that are 

observed in units of different stratigraphic ages, it would be 

useful to constrain the spatial extent across which the stress 

fields are capable of varying and the rate at which major stress 

configurations can change. Within V–14, the most useful tools 

for both aspects are the radial dike systems associated with 

Waka Mons and Asintmah Corona. Emplaced rapidly, and with 

alignments dictated by the stress state of the crust, such dikes 

are stratigraphic markers that yield powerful insight into the 

spatial alignment of tectonic stresses within the dike-intruded 

region at the time the dikes were emplaced. Within 300–500 

km or so of their geographic center the dikes are gently arcuate, but beyond that they have clearly been influenced by local 

stress concentrations. Within V–14, north of their origin, the 

dikes swing one way and then another in response to stress 

concentrations at different coronae and paterae (for example, 

see the deflections occurring near 33.5° N., 206.5° E.), while 

beyond V–14, further to the northeast, the dikes concentrate 

into a narrow belt of deformation aligned with Bellona Fossae, 

for which the V–15 quadrangle is named. The dikes are thus 

highly useful for understanding areas in which regional tectonic 

forces dominate (for example, Bellona Fossae), and those where 

such stresses are minimal leaving the stress field geometries to 

be defined by local stress concentrators (for example, between 

coronae). Constraining the rate at which stress fields can 

change is more difficult given existing data, but some insights 

can still be gained from the Waka/Asintmah dike swarms. The 

major radial elements, extending considerable distances while 

adopting alignments sub-parallel to both Fornax Rupes (V–14) 

and Bellona Fossae (V–15), are subsequently buried by lava 

flows from Waka Mons. These flows in turn are cut by younger 

radial dikes with geometries that do not reflect the presence 

of the regional-scale stress field responsible for producing 

Fornax Rupes and Bellona Fossae. While this does not resolve 

the uncertainty about the rates at which major stress fields can 

change, it does suggest that the time frame required is commensurate with the duration of activity at a major volcanic center. 

Based on data from similar systems on Earth, this suggests that 

major stress patterns across the region may be capable of changing on time frames of a few to at most a few tens of millions of 

years.

Question 3: If mantle upwelling and downwelling 

have played a significant role in the formation of Atla 

Regio and Atalanta Planitia as has been proposed, 

does the geology of Ganiki Planitia record evidence 

of northwest-directed lateral mantle flow connecting 

the two sites?

The V–14 quadrangle lies between the Atla Regio domical highland, an area to the SSE inferred to be a site of active 

mantle upwelling, and the Atalanta Planitia lowlands to the 

northwest, which some have interpreted to be a product of 

mantle downwelling. An explicit goal of this mapping project 

was to determine whether or not there is a regional tectonic 

signature within the quadrangle that suggests the presence of 

lateral mantle flow connecting Atla and Atalanta, a process 

which would be expected to generate (broadly) extensional 

deformation parallel to the flow (that is, roughly NNW) and 

contractional deformation orthogonal to this direction (that is, 

roughly ENE).

Analysis of all mapped lineaments (excluding those within 

the tessera terrains) does not reveal a quadrangle-wide pat-
21

tern indicative of the hypothesized lateral mantle flow, and, 

accordingly, there is no evidence to support the idea that the 

two regions, Atla and Atalanta, are or were dynamically linked. 

There are several possible implications. First, since Atla is a 

modern center of upwelling, it is possible that stresses induced 

by mantle flow outward from Atla have not yet had sufficient 

time to manifest as tectonic deformation in V–14. This seems 

unlikely, however, given the magnitude of the plume-related 

volcanic and tectonic activity in the Atla region, and the probability that activity in this site, though currently ongoing, has 

been long-lived (see Basilevsky, 1993). A second possibility is 

that mantle flow away from the Atla site is preferentially channeled into a specific direction, perhaps by inverted topographic 

variations along the base of the crust/lithosphere. One example 

that seems possible is flow along the course of the rift systems 

that cut Atla, which one would expect to look somewhat necked 

in cross section and which may therefore provide channels for 

preferential mantle flow away from the center of plume upwelling. Available gravity and radar data are currently insufficient to 

test this hypothesis rigorously. Third, it is possible that Atalanta 

is a relict downwelling location, meaning that flow out and 

away from Atla is not in any special sense directed toward the 

Atalanta site. Finally, it is possible that Atalanta is not (and 

was not) a site of downwelling, namely, that it formed via other 

means.

Question 4: Does integration of the tectonic and volcanic histories preserved within the quadrangle help 

constrain competing resurfacing models for Venus?

Exploring whether or not the surface of Venus records 

evidence for catastrophic resurfacing, or if it was resurfaced in 

a uniformitarianism fashion, requires a global-scale synthesis 

and interpretation of the stratigraphy that has been preserved. 

No mapping effort in a single quadrangle-sized area can address 

this question definitively. However, it is the amalgamation of 

observations from individual quadrangles that will yield the data 

necessary to address the matter, and the hope is that stand-alone 

results from individual areas like V–14 will provide insight into 

which hypothesis is most strongly supported. Here we summarize the key components—cratering data and unit stratigraphy—

from within the V–14 quadrangle below.

There are eleven confirmed impact craters in V–14, which 

yields a net crater density of approximately 1.68 per million 

square kilometers, well below the global average of ~2 craters 

per million square kilometers. The small number of craters calls 

into question the validity of inferring any sort of relative age 

from these data, but other aspects of the cratering record, such 

as the presence of dark-halo materials, prove more useful.

While only one crater in the quadrangle, Yablochkina, is 

associated with a massive parabolic deposit, many others are 

surrounded by diffuse radar-dark deposits akin to the larger 

parabolic deposit of Yablochkina. In addition, the small crater 

Unitkak is associated with a spectacular long (~600 km), narrow 

(tens of kilometers) radar dark streak, which we infer to be possible evidence for a low-angle trajectory event. Of the remaining craters, Raymonde lies close to Yablochkina and within its 

parabolic deposit, and this relation prevents clear identification 

of any such signature from Raymonde alone; Clementina is not 

associated with any radar-dark deposits; and Nadira is the only 

crater that has been modified subsequent to emplacement as it 

has been embayed by flows of the youngest regional plains unit 

pr3. Erosion/weathering time hypothesized to remove diffuse, 

radar-dark deposits like the parabolas and similar features is 

predicted to be a few tens to hundreds of millions of years, 

which suggests the bulk of the cratering in the region may 

be disproportionately young, and which, in turn, suggests a 

younger bulk age for the quadrangle than is inferred from the 

crater density alone.

The material unit stratigraphy within the quadrangle is 

difficult to organize into a single comprehensive sequence, but a 

common sequence of transitions from one predominant style of 

geologic activity to another is observed. Critically, there are (a) 

no locations where tesserae are not the oldest unit preserved (if 

they exist in the area), and (b) no locations where evidence of 

“overlap zones” occur, that is places where one region’s tesserae 

(or other stratigraphically older unit) is forming at the expense 

of a stratigraphically younger unit in the same sequence from 

another area in an unexpected fashion. Put another way, there is 

no evidence to suggest that the common stratigraphies observed 

in the different regions formed at different times, although it is 

impossible to eliminate this possibility. Taken together, these 

data could indicate that each local region records a similar 

sequence of transitions occurring at different times and/or rates, 

or that some/all of the local regions endured a general sequence 

of geologic events at about the same time and rate. To gain 

better insight into proposed resurfacing models requires integration of Ganiki Planitia quadrangle’s geologic record with those 

for the surrounding areas.

Acknowledgments

This research was primarily funded by grant NAG5-10157 

from NASA’s Planetary Geology and Geophysics Program, with 

additional support from the Planetary Geology and Geophysics Undergraduate Research Program and Pomona College’s 

Summer Undergraduate Research Program. We are grateful to 

Misha Ivanov, Jim Head, Nick Lang, Carolyn Donlin, Trent 

Hare, Jennifer Blue, and Ken Tanaka for their thorough reviews 

and insightful comments. As the dust settled on this project, a 

group of undergraduates who worked on the project for several 

years and contributed in a significant fashion became coauthors, but many other undergraduate students were involved 

in the project over the years, and I offer my thanks to Madalyn 

Blondes, Thomas Doggett, Warren Katzenstein, Nobu Koch, 

Zach Miller, Nissa Morton, Scott Pelletier, Anjani Polit, and 

Alice Waldron. As first author, I am grateful to everyone who 

has been involved; the interactions we shared certainly kept this 

research endeavor stimulating and fun!

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Figure 3. Cumulative length plots depicting extensional (heavy line) and contractional (lighter line) structures in V–14; only features greater than 30 km in length (that is, largely those shown on the map) are 

depicted. There are far more extensional lineaments than contractional, both in net and at any given structural 

length, and the absolute length achieved by individual extensional features is roughly twice that of the longest 

contractional features. Extensional deformation, occurring mostly during the early- to middle-stages of the 

quadrangle’s stratigraphic evolution, is the dominant outcome for this scale of tectonic deformation in the 

V–14 quadrangle

0 

10,000 

20,000 

30,000 

40,000 

50,000 

60,000 

70,000 

80,000 

90,000 

100,000 

0 50 100 150 200 250 300 350 400 

CUMULATIVE LENGTH, IN KILOMETERS 

LENGTH, IN KILOMETERS 

Contractional 

Extensional 
25

Table 1. Summary of map unit properties within Ganiki Planitia (V–14) quadrangle, Venus.

[dB, decibels; RMS root mean square; deg, degrees]

Symbol Area (km2)1 Backscatter_Adj

(dB)

Topography

(km)2

Emissivity Reflectivity RMS Slope

(deg)

V14 6,583,792 –15.79 0.00 0.874 0.111 2.80

bl 55,095 –15.24 0.23 0.885 0.100 3.46

c 20,157 –13.24 –0.34 0.866 0.137 2.21

cf 9,856 –20.52 –0.13 0.851 0.175 1.15

co 34,147 –15.69 0.08 0.880 0.121 3.64

cof 58,389 –15.05 –0.18 0.880 0.117 2.79

fe 655,409 –14.69 –0.03 0.880 0.104 2.70

pG 156,863 –12.08 0.62 0.892 0.084 3.77

ph 14,811 –19.45 0.34 0.916 0.084 4.31

pl 333,143 –14.28 0.11 0.887 0.091 3.13

pLh 12,547 –12.21 –0.05 0.906 0.066 5.00

pLl 145,969 –12.41 0.39 0.891 0.073 3.44

pr1 861,323 –13.62 0.18 0.889 0.087 3.08

pr2 2,660,025 –17.84 –0.11 0.863 0.127 2.45

pr3 611,665 –15.46 –0.45 0.863 0.128 2.65

ps 552,131 –16.36 0.04 0.874 0.110 2.78

t 391,217 –12.31 0.43 0.903 0.081 4.01

1All values reflect area-normalized calculations; the area modified by airburst craters covers another 11,000 km2. 2All topography values given relative to the mean elevation for V–14 quadrangle or 6,051.58 km.
26

Table 2. Individual map unit properties and names for every geographically distinct example of each unit, ranged alphabetically by map symbol and then by increasing area. Each entry in the table corresponds to single discrete example (for example, closed polygon) of the unit. The unit latitude and longitude provided each table entry is the centroid location calculated within ArcGIS.

Backscatter_Adj (dB) Topography (km)a Emissivity Reflectivity RMS Slope (de

Symbol Lat (deg N) Long (deg E) Area (km2) 

Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sig

bl 44.46 195.72 4,459 –17.58 3.97 0.55 0.30 0.881 0.008 0.106 0.022 2.99 1.2bl 43.94 192.10 5,164 –17.46 3.75 0.78 0.26 0.870 0.010 0.120 0.007 2.66 0.3bl 41.05 192.98 8,363 –12.87 2.71 0.25 0.17 0.894 0.009 0.093 0.007 3.65 0.9bl 41.05 196.00 11,382 –14.02 2.73 0.21 0.22 0.886 0.011 0.102 0.014 3.79 1.0bl 45.83 208.15 25,727 –15.69 3.97 0.07 0.20 0.885 0.007 0.097 0.008 3.49 0.7

c 35.87 208.61 170 –14.17 2.71 –0.20 0.05 0.877 0.001 0.121 –0.002 2.81 0.1c 29.02 182.02 253 –13.65 3.36 0.28 0.02 0.868 0.002 0.102 –0.001 2.32 0.0c 48.41 191.44 312 –19.28 3.18 –0.12 0.03 0.811 0.004 0.197 0.009 1.78 0.1c 32.65 208.66 398 –13.33 3.40 0.17 0.06 0.872 0.002 0.105 0.002 2.45 0.0c 40.86 199.46 442 –14.96 3.35 –0.21 0.02 0.866 0.001 0.124 0.000 2.16 0.1c 30.68 187.28 694 –11.31 3.30 0.50 0.22 0.886 0.001 0.084 0.000 3.38 0.5c 37.23 207.86 703 –12.61 3.50 0.04 0.07 0.842 0.004 0.148 0.012 2.24 0.4c 34.92 205.81 737 –14.09 3.53 –0.43 0.04 0.876 0.004 0.108 0.005 2.06 0.4c 32.28 195.25 797 –13.78 2.08 0.01 0.07 0.884 0.001 0.101 0.001 2.34 0.1c 33.77 185.05 978 –14.23 3.73 –0.59 0.03 0.890 0.006 0.106 0.009 2.23 0.8c 44.14 201.58 2,741 –13.71 2.84 –0.47 0.17 0.877 0.004 0.111 0.011 2.73 0.7c 48.33 195.39 11,931 –12.87 3.56 –0.42 0.37 0.861 0.023 0.152 0.030 2.02 0.8

cf 48.40 195.19 9,856 –20.52 2.62 –0.13 0.14 0.851 0.019 0.175 0.032 1.15 0.3

co 49.07 202.62 34,147 –15.69 3.33 0.08 0.39 0.880 0.008 0.121 0.019 3.64 1.0

cof 32.46 205.08 3,733 –13.76 2.80 –0.10 0.21 0.896 0.009 0.090 0.008 2.81 1.1cof 33.43 204.43 15,145 –13.76 2.80 –0.10 0.21 0.896 0.009 0.090 0.008 2.81 1.1cof 48.06 204.44 39,511 –15.67 2.58 –0.21 0.23 0.873 0.009 0.130 0.015 2.78 0.7

fe 40.85 209.96 264 –16.16 4.35 –0.27 0.22 0.884 0.008 0.100 0.000 3.45 0.5fe 42.80 195.45 287 –18.74 2.11 –0.04 0.04 0.845 0.002 0.155 –0.002 2.08 0.0fe 30.35 205.84 1,972 –15.39 2.30 0.21 0.15 0.883 0.003 0.091 0.001 3.09 0.3fe 42.41 195.94 2,561 –18.77 2.03 –0.34 0.04 0.842 0.009 0.189 0.014 1.85 0.2fe 36.60 209.62 4,128 –14.94 2.29 0.24 0.11 0.887 0.009 0.098 0.005 3.46 0.5fe 25.29 196.35 4,553 –12.86 2.08 1.04 0.20 0.910 0.008 0.073 0.005 3.16 0.7fe 38.54 206.57 6,761 –14.52 2.31 –0.36 0.17 0.862 0.011 0.123 0.004 2.99 0.5fe 28.37 199.19 14,246 –10.97 2.57 0.28 0.24 0.914 0.009 0.088 0.006 4.08 1.2fe 44.80 184.77 18,202 –17.10 2.93 –0.03 0.56 0.857 0.005 0.142 0.019 3.24 0.7fe 32.40 206.97 18,361 –12.57 2.65 0.00 0.19 0.906 0.007 0.084 0.006 3.51 1.0fe 38.95 203.24 21,334 –15.57 2.57 –0.43 0.28 0.867 0.011 0.123 0.014 3.38 0.9fe 27.69 196.87 22,649 –11.66 2.51 0.28 0.45 0.909 0.008 0.081 0.008 4.30 1.5fe 30.12 207.07 26,152 –14.68 2.32 0.08 0.12 0.872 0.007 0.099 0.005 3.16 0.8fe 34.20 198.61 30,354 –14.66 2.35 –0.12 0.23 0.872 0.009 0.108 0.009 3.27 0.7fe 26.04 197.23 30,661 –11.97 2.78 0.59 0.38 0.904 0.009 0.085 0.008 3.19 1.1fe 40.13 194.00 44,093 –15.68 2.65 –0.14 0.28 0.878 0.012 0.110 0.014 2.83 0.5fe 39.18 207.10 58,585 –15.01 2.28 –0.46 0.20 0.868 0.011 0.121 0.010 2.83 0.7fe 40.36 206.75 64,329 –15.73 2.42 –0.50 0.20 0.866 0.011 0.119 0.010 2.29 0.4
27

Table 2. Individual map unit properties and names for every geographically distinct example of each unit, 

ranged alphabetically by map symbol and then by increasing area. Each entry in the table corresponds to single discrete example (for example, closed polygon) of the unit. The unit latitude and longitude provided each table entry is the centroid location calculated within ArcGIS—continued.

Backscatter_Adj (dB) Topography (km)a Emissivity Reflectivity RMS Slope (de

Symbol Lat (deg N) Long (deg E) Area (km2) 

Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sig

fe 35.78 208.60 72,653 –14.96 2.54 –0.16 0.33 0.886 0.015 0.103 0.011 3.11 0.8fe 26.62 206.63 213,265 –14.84 2.61 0.18 0.19 0.881 0.015 0.096 0.013 1.94 0.6

pG 26.31 183.82 156,863 –12.08 2.72 0.62 0.25 0.892 0.012 0.084 0.007 3.77 1.0

ph 44.41 193.57 14,811 –19.45 2.27 0.34 0.13 0.916 0.021 0.084 0.014 4.31 1.2

pl 37.02 209.88 386 –14.94 2.29 0.24 0.11 0.887 0.009 0.098 0.005 3.46 0.5pl 37.22 209.23 625 –14.94 2.29 0.24 0.11 0.887 0.009 0.098 0.005 3.46 0.5pl 37.70 202.07 1,451 –17.17 2.72 0.26 0.14 0.844 0.006 0.136 0.007 3.19 0.7pl 45.18 196.76 1,898 –18.68 3.61 –0.05 0.21 0.865 0.006 0.129 0.036 1.71 0.3pl 35.27 190.33 2,007 –12.97 2.43 0.38 0.24 0.898 0.004 0.070 0.003 2.91 0.2pl 31.97 182.82 2,167 –15.98 3.01 –0.13 0.20 0.866 0.011 0.096 0.007 3.53 0.4pl 32.37 181.66 2,293 –14.02 2.60 –0.11 0.12 0.884 0.009 0.092 0.001 3.76 1.1pl 31.51 205.33 2,709 –13.04 2.51 –0.03 0.11 0.912 0.006 0.086 0.013 4.90 1.3pl 31.45 181.57 2,908 –14.10 2.55 0.33 0.15 0.890 0.007 0.091 0.009 5.10 1.0pl 37.15 198.37 3,654 –14.87 2.79 –0.05 0.05 0.876 0.007 0.112 0.004 2.46 0.2pl 33.58 208.88 3,864 –12.73 2.57 0.27 0.15 0.904 0.005 0.086 0.008 3.75 1.0pl 28.18 208.91 5,412 –12.76 2.84 0.32 0.12 0.896 0.011 0.081 0.003 2.57 0.7pl 35.84 207.22 5,482 –13.57 2.77 –0.28 0.19 0.889 0.008 0.104 0.007 3.70 0.8pl 44.96 191.66 7,870 –18.57 3.75 0.94 0.17 0.858 0.011 0.136 0.012 2.04 0.5pl 26.18 202.49 9,871 –13.99 2.48 0.29 0.19 0.880 0.011 0.083 0.002 3.03 0.5pl 27.32 203.92 11,524 –14.62 2.45 0.28 0.21 0.881 0.005 0.092 0.009 3.49 1.1pl 29.16 205.62 13,770 –14.76 2.37 0.37 0.18 0.879 0.008 0.101 0.011 3.83 1.3pl 37.84 201.05 45,063 –15.66 2.82 –0.05 0.20 0.863 0.015 0.116 0.010 2.72 0.5pl 37.66 184.77 66,916 –14.18 2.62 0.17 0.25 0.886 0.010 0.089 0.007 2.99 0.6pl 36.03 194.83 143,273 –13.66 2.66 0.04 0.23 0.899 0.012 0.080 0.006 3.21 0.8

pLh 28.37 187.51 12,547 –12.21 2.74 –0.05 0.32 0.906 0.006 0.066 0.007 5.00 1.4

pLl 28.64 188.04 1,222 –10.41 3.08 0.46 0.17 0.907 0.002 0.072 0.004 4.87 1.4pLl 27.76 191.15 3,600 –12.35 2.34 0.39 0.12 0.906 0.008 0.074 0.005 3.97 0.6pLl 30.97 187.73 4,754 –13.68 3.52 0.03 0.21 0.884 0.004 0.075 0.007 3.96 1.1pLl 32.05 190.46 11,601 –11.47 2.56 0.13 0.13 0.899 0.008 0.071 0.002 3.22 0.7pLl 27.55 187.52 16,066 –11.61 2.67 0.07 0.18 0.904 0.008 0.067 0.002 3.67 1.0pLl 29.73 188.34 21,251 –13.35 2.70 0.28 0.18 0.888 0.009 0.073 0.004 3.12 0.7pLl 26.25 190.71 87,476 –12.42 2.43 0.52 0.26 0.888 0.014 0.075 0.004 3.43 0.9

pr1 39.03 202.42 447 –16.65 1.87 –0.51 0.08 0.864 0.002 0.115 –0.001 2.98 0.4pr1 25.28 195.71 572 –12.48 1.98 0.84 0.06 0.923 0.006 0.070 –0.001 2.99 0.6pr1 25.25 195.19 699 –12.33 2.05 0.52 0.12 0.920 0.002 0.061 0.002 2.78 0.6pr1 26.06 190.46 880 –14.13 2.02 0.49 0.07 0.880 0.005 0.072 0.001 2.48 0.1pr1 40.01 180.21 1,066 –14.99 2.71 0.51 0.18 0.884 0.003 0.094 0.006 3.42 0.5pr1 35.76 182.19 2,232 –15.47 2.35 –0.12 0.11 0.865 0.004 0.102 0.006 2.39 0.2pr1 35.37 191.42 2,417 –12.79 2.13 0.18 0.15 0.898 0.005 0.076 0.001 2.83 0.5pr1 26.99 187.11 4,650 –13.03 2.31 0.25 0.17 0.881 0.011 0.076 0.003 2.78 0.3
28

Table 2. Individual map unit properties and names for every geographically distinct example of each unit, 

ranged alphabetically by map symbol and then by increasing area. Each entry in the table corresponds to single discrete example (for example, closed polygon) of the unit. The unit latitude and longitude provided each table entry is the centroid location calculated within ArcGIS—continued.

Backscatter_Adj (dB) Topography (km)a Emissivity Reflectivity RMS Slope (de

Symbol Lat (deg N) Long (deg E) Area (km2) 

Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sig

pr1 34.42 208.72 5,641 –14.58 2.20 0.11 0.07 0.900 0.006 0.083 0.003 3.12 0.5pr1 31.15 182.14 18,322 –16.48 2.38 0.16 0.26 0.872 0.008 0.091 0.005 3.14 0.8pr1 25.67 180.80 22,407 –13.60 2.52 0.75 0.18 0.874 0.008 0.093 0.008 4.01 1.0pr1 32.16 185.45 43,536 –15.55 2.72 –0.28 0.28 0.870 0.009 0.103 0.016 3.51 1.4pr1 33.55 192.81 94,107 –12.66 2.28 –0.17 0.20 0.870 0.017 0.101 0.016 2.03 0.4pr1 29.59 200.23 664,348 –13.55 2.69 0.24 0.37 0.894 0.013 0.084 0.009 3.17 1.1pr2 28.40 194.21 217 –14.42 2.74 –0.96 0.05 0.911 0.004 0.075 0.000 2.09 0.0pr2 28.28 192.22 316 –15.52 3.26 –0.01 0.08 0.885 0.005 0.078 –0.001 2.24 0.4pr2 42.42 209.87 454 –18.58 2.74 –0.52 0.01 0.866 0.003 0.126 0.003 2.38 0.3pr2 44.05 193.35 556 –23.33 2.01 0.29 0.02 0.941 0.003 0.053 0.001 3.28 0.4pr2 28.78 193.55 569 –15.94 2.27 –0.37 0.18 0.913 0.003 0.080 0.000 2.38 0.9pr2 29.34 195.97 634 –16.83 2.35 –0.71 0.12 0.892 0.006 0.098 0.009 2.02 0.3pr2 43.68 204.32 671 –15.59 2.50 –0.28 0.11 0.862 0.002 0.136 0.010 4.23 0.8pr2 25.88 185.89 1,256 –14.54 2.21 0.74 0.09 0.895 0.003 0.063 –0.003 3.00 0.1pr2 35.43 195.53 1,413 –15.56 2.22 –0.05 0.06 0.891 0.002 0.083 0.001 1.97 0.3pr2 41.77 208.91 2,106 –16.93 1.87 –0.37 0.11 0.868 0.003 0.114 0.001 2.08 0.2pr2 43.94 201.37 3,093 –16.11 2.40 –0.36 0.18 0.870 0.004 0.129 0.011 2.83 0.6pr2 29.03 209.50 3,268 –15.91 2.54 –0.12 0.06 0.876 0.011 0.116 0.013 1.77 0.3pr2 42.40 205.29 3,269 –15.56 2.07 –0.87 0.06 0.886 0.006 0.115 0.006 1.90 0.3pr2 46.78 201.99 4,812 –16.83 2.67 –0.29 0.35 0.858 0.003 0.148 0.018 3.02 0.8pr2 36.49 195.28 5,485 –16.36 2.42 –0.36 0.07 0.898 0.009 0.092 0.005 2.02 0.3pr2 43.49 195.74 6,843 –19.31 2.80 0.24 0.29 0.860 0.012 0.130 0.016 2.41 0.5pr2 38.09 197.47 7,247 –17.76 2.01 –0.31 0.07 0.874 0.006 0.119 0.005 2.10 0.3pr2 27.72 209.41 7,507 –16.40 2.62 0.08 0.09 0.880 0.009 0.111 0.018 1.12 0.2pr2 33.83 208.14 12,930 –16.63 2.29 –0.03 0.07 0.893 0.007 0.097 0.006 2.06 0.3pr2 41.78 202.52 20,259 –14.81 2.58 –0.71 0.27 0.866 0.006 0.125 0.011 2.36 0.7pr2 28.30 204.21 37,308 –15.81 2.41 0.17 0.15 0.880 0.009 0.094 0.007 2.73 0.5pr2 36.80 204.32 142,461 –18.16 3.22 –0.03 0.28 0.851 0.016 0.130 0.013 2.68 0.8pr2 46.33 207.63 156,555 –16.59 2.30 –0.09 0.26 0.879 0.009 0.113 0.013 2.48 0.7pr2 34.35 197.60 306,015 –16.34 2.71 –0.07 0.30 0.873 0.014 0.111 0.017 2.25 0.7pr2 41.42 188.08 1,934,778 –18.26 3.25 –0.12 0.37 0.860 0.020 0.132 0.031 2.46 0.7pr3 40.04 209.97 42 –15.99 4.79 –0.32 0.01 0.861 0.001 0.110 –0.005 2.80 –0.1pr3 29.54 182.92 1,284 –15.27 2.34 0.09 0.10 0.885 0.010 0.083 0.006 3.72 0.9pr3 40.22 209.22 3,468 –15.24 2.23 –0.39 0.04 0.865 0.005 0.126 0.003 3.14 0.2pr3 49.72 181.07 4,218 –15.73 2.28 –0.95 0.06 0.839 0.001 0.159 0.004 2.52 0.2pr3 39.75 204.54 4,953 –15.58 1.77 –0.53 0.12 0.875 0.007 0.110 0.009 2.54 0.3pr3 49.46 183.75 6,522 –17.00 1.96 –0.75 0.06 0.840 0.003 0.166 0.003 2.45 0.2pr3 30.68 180.63 7,636 –15.90 2.02 0.03 0.07 0.859 0.004 0.120 0.004 2.85 0.2pr3 44.15 180.64 7,845 –15.98 2.05 –0.36 0.21 0.856 0.004 0.138 0.009 3.12 0.2pr3 39.20 209.44 8,014 –14.13 2.16 –0.37 0.11 0.857 0.013 0.119 0.007 2.89 0.5
29

Table 2. Individual map unit properties and names for every geographically distinct example of each unit, 

ranged alphabetically by map symbol and then by increasing area. Each entry in the table corresponds to single discrete example (for example, closed polygon) of the unit. The unit latitude and longitude provided each table entry is the centroid location calculated within ArcGIS—continued.

Backscatter_Adj (dB) Topography (km)a Emissivity Reflectivity RMS Slope (de

Symbol Lat (deg N) Long (deg E) Area (km2) 

Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sig

pr3 28.55 205.77 10,395 –14.19 1.98 0.17 0.12 0.870 0.008 0.098 0.004 2.74 0.5pr3 36.55 207.38 32,282 –15.92 2.41 –0.09 0.15 0.856 0.011 0.134 0.014 2.43 0.5pr3 42.66 202.14 525,006 –15.44 2.38 –0.49 0.21 0.863 0.012 0.128 0.016 2.65 0.5

ps 29.80 191.92 1,110 –15.02 2.65 –0.71 0.42 0.906 0.008 0.079 0.006 3.26 0.7ps 29.75 191.00 1,136 –13.37 2.53 –0.81 0.32 0.888 0.004 0.083 0.014 5.12 1.3ps 30.02 192.30 3,979 –13.81 2.16 –0.49 0.18 0.888 0.010 0.086 0.003 1.95 0.5ps 30.08 209.72 5,041 –14.46 2.63 –0.01 0.24 0.896 0.005 0.101 0.009 2.88 0.3ps 46.02 187.70 5,140 –20.43 2.65 0.31 0.11 0.832 0.002 0.157 0.008 2.61 0.2ps 49.74 209.27 6,123 –14.09 2.46 –0.11 0.14 0.884 0.004 0.115 0.007 3.66 0.5ps 37.64 206.37 9,613 –17.45 3.18 –0.51 0.24 0.844 0.006 0.147 0.019 2.40 0.6ps 45.22 190.83 12,477 –17.30 3.62 0.69 0.22 0.862 0.023 0.122 0.023 2.82 1.0ps 38.68 180.42 12,620 –15.69 2.58 0.06 0.32 0.880 0.006 0.093 0.005 3.00 0.6ps 44.28 190.31 13,103 –18.74 2.91 0.47 0.30 0.867 0.016 0.121 0.019 2.75 0.6ps 49.51 204.36 16,398 –16.90 2.33 –0.57 0.17 0.887 0.008 0.116 0.011 2.23 0.5ps 49.48 201.47 19,412 –17.58 2.68 –0.45 0.25 0.878 0.007 0.125 0.008 2.71 0.5ps 39.80 189.33 23,539 –16.03 2.00 –0.01 0.16 0.867 0.016 0.115 0.015 2.49 0.4ps 39.98 183.15 32,664 –15.54 2.15 –0.11 0.20 0.874 0.010 0.113 0.008 3.05 0.7ps 44.92 195.74 83,797 –20.58 3.86 0.06 0.43 0.873 0.023 0.134 0.033 2.33 1.0ps 34.65 186.30 88,674 –14.89 2.59 –0.10 0.18 0.880 0.010 0.088 0.009 2.86 0.8ps 33.09 201.02 217,304 –15.20 2.78 0.18 0.39 0.873 0.016 0.105 0.013 2.93 0.9

t 45.41 193.22 68 –16.75 4.45 0.81 0.09 0.881 0.002 0.099 –0.001 1.60 0.1t 29.58 188.01 151 –12.57 2.91 0.51 0.04 0.891 0.002 0.061 –0.002 2.55 0.2t 28.33 202.09 169 –13.38 2.84 0.51 0.03 0.880 0.002 0.091 –0.002 2.10 0.0t 34.05 188.73 181 –11.75 2.75 0.03 0.04 0.888 0.002 0.061 –0.003 2.43 0.4t 40.62 181.15 209 –14.23 3.19 –0.16 0.03 0.877 0.002 0.123 0.001 2.40 0.3t 27.69 191.69 223 –11.77 2.73 0.21 0.04 0.882 0.004 0.085 –0.004 3.44 0.3t 36.62 199.06 264 –13.09 3.17 –0.09 0.00 0.853 0.003 0.132 0.001 2.55 0.0t 27.04 187.69 272 –10.40 2.68 0.22 0.10 0.893 0.005 0.074 –0.002 3.91 0.2t 36.29 199.99 307 –13.05 3.35 –0.17 0.02 0.860 0.004 0.120 –0.001 2.68 0.2t 27.99 202.39 341 –13.46 2.85 0.29 0.04 0.881 0.002 0.087 –0.002 2.71 0.1t 41.46 189.64 373 –14.40 3.44 0.41 0.02 0.855 0.003 0.133 0.001 2.43 0.1t 34.81 184.05 388 –13.63 3.05 –0.09 0.05 0.882 0.002 0.101 –0.003 3.25 0.4t 34.99 181.54 413 –13.90 3.48 –0.25 0.02 0.875 0.003 0.107 –0.001 1.82 0.0t 29.65 188.52 433 –12.02 3.10 –0.01 0.11 0.879 0.006 0.072 –0.003 3.68 0.2t 36.72 198.15 453 –12.70 3.19 –0.15 0.03 0.879 0.005 0.106 0.001 1.94 0.0t 45.39 193.44 457 –17.82 4.13 0.76 0.11 0.898 0.011 0.103 0.011 1.84 0.4t 33.65 191.48 458 –11.57 2.92 –0.21 0.03 0.884 0.001 0.085 0.003 2.16 0.1t 34.98 182.07 462 –14.13 3.27 –0.26 0.03 0.876 0.005 0.119 –0.002 1.89 0.1t 29.45 188.33 494 –12.78 3.12 0.35 0.12 0.883 0.003 0.068 0.002 3.39 0.2t 27.91 202.01 536 –12.78 2.77 0.45 0.06 0.891 0.003 0.095 0.012 3.38 1.0
30

Table 2. Individual map unit properties and names for every geographically distinct example of each unit, 

ranged alphabetically by map symbol and then by increasing area. Each entry in the table corresponds to single discrete example (for example, closed polygon) of the unit. The unit latitude and longitude provided each table entry is the centroid location calculated within ArcGIS—continued.

Backscatter_Adj (dB) Topography (km)a Emissivity Reflectivity RMS Slope (de

Symbol Lat (deg N) Long (deg E) Area (km2) 

Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sigma Mean 1 Sig

t 36.80 200.83 574 –12.22 3.06 –0.27 0.17 0.883 0.005 0.106 0.005 3.52 0.5t 30.43 186.48 623 –14.50 3.29 0.30 0.08 0.898 0.004 0.080 0.002 3.11 0.6t 27.10 188.24 816 –9.95 2.62 –0.05 0.08 0.895 0.006 0.077 –0.002 4.43 0.6t 27.69 187.52 897 –10.08 2.59 –0.06 0.41 0.910 0.003 0.070 0.000 4.87 1.2t 25.11 200.42 920 –12.50 3.04 0.30 0.07 0.887 0.008 0.069 0.000 3.14 0.3t 34.24 189.18 1,082 –12.74 2.89 –0.23 0.08 0.885 0.003 0.078 0.002 1.74 0.1t 37.79 190.02 1,188 –12.43 2.84 0.09 0.10 0.874 0.007 0.086 0.003 2.84 0.4t 28.02 188.58 1,394 –10.80 2.68 0.20 0.26 0.915 0.002 0.070 0.003 5.57 1.2t 36.09 182.31 1,461 –13.29 2.78 –0.13 0.07 0.877 0.005 0.106 0.004 3.24 0.4t 30.16 182.22 1,588 –14.39 2.83 0.36 0.29 0.883 0.009 0.096 0.010 6.90 1.9t 26.01 191.89 1,806 –10.73 2.63 0.97 0.14 0.915 0.006 0.077 0.009 4.72 1.2t 37.05 209.48 1,841 –13.09 2.81 0.25 0.09 0.901 0.006 0.100 0.010 4.69 1.4t 27.65 188.24 1,935 –10.58 2.66 –0.01 0.19 0.916 0.004 0.066 0.003 5.91 1.1t 35.85 180.30 3,189 –14.27 3.39 –0.19 0.07 0.883 0.011 0.103 0.005 2.79 1.0t 25.81 199.06 3,679 –10.60 2.84 0.37 0.09 0.918 0.009 0.083 0.005 4.47 1.3t 47.31 181.14 3,736 –14.81 3.25 –0.57 0.12 0.862 0.009 0.131 0.006 2.64 0.7t 29.14 182.81 4,684 –14.25 3.20 0.51 0.25 0.887 0.006 0.082 0.012 4.04 0.9t 35.97 184.91 4,930 –12.31 2.79 –0.05 0.24 0.896 0.008 0.085 0.009 4.13 1.0t 34.89 180.98 5,250 –13.32 3.16 –0.35 0.31 0.890 0.012 0.099 0.010 4.00 2.3t 47.57 187.61 5,847 –17.95 4.12 0.09 0.13 0.827 0.008 0.157 0.023 2.35 0.7t 33.91 192.47 6,121 –12.37 3.06 0.25 0.27 0.892 0.010 0.085 0.003 3.02 0.5t 28.18 186.31 6,250 –12.18 2.79 0.07 0.35 0.910 0.006 0.075 0.004 4.41 1.1t 28.72 188.96 6,756 –11.37 3.04 0.30 0.16 0.897 0.006 0.075 0.004 3.80 0.9t 28.97 187.31 7,798 –11.26 2.97 0.42 0.30 0.901 0.006 0.074 0.008 4.93 1.6t 27.33 190.73 8,696 –11.04 2.76 0.51 0.19 0.906 0.009 0.075 0.006 4.65 1.5t 32.15 187.13 11,585 –13.44 3.05 –0.12 0.14 0.888 0.009 0.082 0.006 3.43 1.0t 27.77 201.31 11,828 –11.38 2.92 0.71 0.24 0.905 0.012 0.084 0.011 4.28 1.7t 34.43 182.92 11,963 –13.26 3.05 –0.22 0.20 0.892 0.012 0.090 0.011 3.91 1.8t 34.88 191.00 12,930 –11.70 2.74 0.23 0.29 0.897 0.009 0.071 0.003 3.44 0.9t 40.01 181.19 16,066 –13.68 2.98 0.35 0.25 0.887 0.009 0.088 0.006 3.69 0.8t 30.18 187.42 17,285 –12.30 3.38 0.36 0.22 0.891 0.008 0.086 0.009 4.24 1.7t 46.15 194.14 18,024 –15.77 3.85 0.81 0.56 0.878 0.012 0.094 0.016 3.13 1.0t 40.91 186.26 24,088 –13.13 3.25 0.54 0.30 0.889 0.015 0.092 0.009 3.77 1.1t 32.44 180.71 28,374 –12.32 3.24 0.20 0.24 0.914 0.012 0.081 0.012 4.95 1.9t 31.63 189.17 60,484 –11.32 2.93 0.41 0.31 0.906 0.011 0.071 0.004 4.29 1.5t 26.58 194.08 88,881 –11.37 2.92 0.86 0.23 0.928 0.012 0.071 0.005 4.01 1.4

1Izumi Patera and Razia Patera preserve no unique material units, and hence are not listed here