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Geologic Map of the Lada Terra Quadrangle (V–56), Venus

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Prepared for the National Aeronautics and Space Administration Geologic Map of the Lada Terra Quadrangle (V–56), Venus By P. Senthil Kumar and James W. Head Pamplet to accompany Scientific Investigations Map 3249 75° 75° V–1 V–6 V–3 50° 50° V–7 V–2 V–17 V–10 V–18 V–9 V–19 V–8 25° 25° V–29 V–22 V–30 V–21 V–31 V–20 270° 300° 330° 0° 30° 60° 90° 0° 0° V–43 V–32 V–42 V–33 V–41 V–34 –25° –25° V–55 V–44 V–54 V–45 V–53 V–46 V–61 V–56 –50° –50° V–60 V–57 V–62 –75° –75° 2013 U.S. Department of the Interior U.S. Geological Survey Contents Introduction.....................................................................................................................................................1 Magellan SAR Data and Analysis ...............................................................................................................1 General Geology.............................................................................................................................................2 Map Units ........................................................................................................................................................3 Heavily Deformed Terrain Material ....................................................................................................3 Tessera Terrain Material ............................................................................................................3 Tessera-like Terrain Material .....................................................................................................3 Densely Lineated Terrain Material ............................................................................................4 Regional Plains Material .....................................................................................................................4 Wrinkle Ridged Plains Material .................................................................................................4 Regional Plains Material ............................................................................................................4 Volcanogenic Plains Material .............................................................................................................4 Shield Plains Material .................................................................................................................4 Intra-tessera Basin Plains Material .........................................................................................5 Lobate Plains Material ................................................................................................................5 Impact Crater Material ........................................................................................................................5 Structures........................................................................................................................................................5 Primary Structures................................................................................................................................5 Shields ...........................................................................................................................................5 Channels ........................................................................................................................................5 Lobate Flow Fronts.......................................................................................................................6 Impact Crater Rim ........................................................................................................................6 Secondary Structures ..........................................................................................................................6 Lineaments ....................................................................................................................................6 Fractures .......................................................................................................................................6 Faults..............................................................................................................................................6 Grabens .........................................................................................................................................6 Linear Ridges ................................................................................................................................6 Wrinkle Ridges .............................................................................................................................6 Stratigraphic Relations .................................................................................................................................7 Geologic History .............................................................................................................................................8 Summary..........................................................................................................................................................8 Acknowledgments ........................................................................................................................................9 References Cited............................................................................................................................................9 Table 1. Morphology of impact craters in Lada Terra quadrangle (V–56), Venus ....................................11 iii Geologic Map of the Lada Terra Quadrangle (V–56), Venus By P. Senthil Kumar1,2 and James W. Head2 Introduction processes relating to the convergence and divergence in Lavinia Planitia, Lada Terra, and Derceto Corona. Lopez and others (1999) found similarities between the coronae-extensional Geologic mapping provides fundamental information on belts in Lada Terra and the East African rift system on Earth. the distribution of material units and structural geologic features Stofan and others (1992) studied the morpho-structural char- on a planetary surface and establishes age relations among these acteristics of some of the coronae (Quetzalpetlatl, Eithinoha, units. By understanding the petrogenesis of mapped material and Sarpanitum) in Lada Terra and suggested the mechanism units and the tectonic history from the deformational structures, of coronae formation related to the mantle plumes. Kratter and the geologic map provides significant insight into the processes others (2007) studied the Arecibo radar images of Quetzalpetlatl of crustal evolution. On Earth, geologists prepare geologic maps Corona and surrounding regions and identified several pahohae in various spatial scales by carrying out field geologic analyses, lava flows emanating from Quetzalpetlatl Corona and a few new whereas orbiter images are extensively used in preparing global impact craters. Based on a detailed geological mapping and top- or local geologic maps of other planetary surfaces. On Venus, ographic analysis, Ivanov and Head (2010b) showed that Lada although previous missions such as Venera 15/16 and Arecibo Terra rise and Quetzalpetlatl Corona form a region of long-lived Earth-based radar observations showed a variety of surface geo- mantle upwelling and recent volcanic activity. Although the logic features, the Magellan mission provided a global coverage above studies provided many insights to the material units and of radar images (~98%), and these images were used in prepar- structural features and the attendant geologic processes in Lada ing a global geologic map (Ivanov and Head, 2011). Terra, this publication provides a geologic map of the entire This publication provides a geological map of Lada Terra Lada Terra (V–56) quadrangle and reconstructs the geologic quadrangle (V–56), a portion of the southern hemisphere of history within the quadrangle. Venus that extends from lat 50° S. to 70° S. and from long 0° E. to 60° E. V–56 is bordered by Kaiwan Fluctus (V–44) (Bridges and McGill, 2002) and Agnesi (V–45) quadrangles in the north and by Mylitta Fluctus (V–61) (Ivanov and Head, 2006), Magellan SAR Data and Analysis Fredegonde (V–57) (Ivanov and Head, 2010a), and Hurston (V–62) quadrangles in the west, east, and south, respectively. The geological map of V–56 quadrangle reveals evidence The orbiting phase of the Magellan mission extended from for tectonic, volcanic, and impact processes in Lada Terra in August 10, 1990, to October 12, 1994. During mission cycles 1, the form of tesserae, regional extensional belts, coronae, and 2, and 3 from September 1990 to September 1992, the space- volcanic plains. In addition, the map also shows relative age craft collected synthetic aperture radar (SAR) images, passive relations such as overlapping or cross-cutting relations between microwave thermal emissions, and measurements of backscatter the mapped geologic units. The geology observed within this power at small angle of incidence, covering ~98 percent of the quadrangle addresses (1) how coronae evolved in association surface of Venus. During mission cycles 4, 5, and 6 from Sep- with regional extensional belts and (2) how tesserae, regional tember 1992 and October 1994, high-resolution gravity mea- plains, and impact craters, which are also significant geological surements were made. The SAR instrument operated at a wave- units observed in Lada Terra quadrangle, were formed. length of 12.6 cm (S-band) with horizontal transmit/receive Several previous
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