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1 GSA Data Repository Item Appendix A: Technical details of ASTER image of Lonar crater Multi-spectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery, acquired on April 8, 2003 and January 21, 2004 at a.m. (IST) (LPDAAC, 2007), was used to investigate the shape of the Lonar crater and distribution of ejecta around it (Fig. 1a). The ASTER is the Earth s first spaceborne multispectral Thermal Infrared Radiometer (TIR) instrument that has recently been used to obtain and interpret high spatial resolution images of terrestrial geological features including asteroid impact craters (e.g., Rowan et al., 2005; Wright and Ramsay, 2006). The Lonar crater was also examined with a panchromatic Landsat 7 image of 15 m spatial resolution (Misra et al., 2006). The advantage of the ASTER image is that it produces a better image in the same spatial resolution (15m) in the Visible and Near-Infrared Radiometer (VNIR) bands and better spectral resolution in the Short Wave Infrared Radiometer (SWIR) (6 bands) and Thermal Infrared Radiometer (TIR) bands (5 bands) as well. A higher number of SWIR and TIR bands also provide important information on mineral composition on land surfaces (Vaughan et al., 2005). Two scenes captured on different dates (see above) were obtained to minimize the effect of the sun angle and enhanced the shape of the Lonar crater Appendix B: Sampling and Experimental techniques of AMS study of Lonar crater Oriented drill core samples of diameter 2.5 cm along the Lonar crater rim and adjacent area were collected (Fig. 1d) during our June 2008 field trip using a gasoline-powered rock drill. We collected basalt samples from locations (one each) from the eastern, southeastern, southern, southwestern, western and northwestern sectors of the crater rim. The target basalt at the northern crater rim was extremely brittle in nature and it was very difficult to collect drill cores of full length (~7-9 cm) from this sector. Therefore, drill cores of relatively smaller length (3-5 cm) from two locations at this sector were collected. No sampling was possible from the northeastern crater rim sector because of the absence of a rim in this part of the crater due to faulting (Fig. 1a). Cores were

2 cut into four cylindrical specimens in maximum of height 2.2 cm each in the laboratory. The AMS (low-field) was measured using an AGICO (Czech Republic) KLY-4S Kappabridge with an alternating field intensity of 300 A/m and an operating frequency of 875 Hz (AGICO, 2004) at the Environmental Magnetism Laboratory, Indian Institute of Geomagnetism, Navi Mumbai, India. The specimen susceptibility was measured manually in fifteen different orientations following a rotatable design, from which six independent components of the susceptibility tensor and statistical errors were calculated using the software SUFAM (Jelinek, 1978). Additional drill core samples were also collected during our February 2009 field trip and two to four specimens of height 2.0 cm each were cut from the each drill core for measurement of AMS in spinning specimen method using the same instrument. In this technique 64 x 3 measurements were made along three orthogonal directions with reference to the drill core axis of each specimen and the software SUFAR was used for computation of the AMS parameters. Besides the studies on the orientations of AMS principal susceptibility axes, the following two mathematical parameters (after Jelinek, 1978) were also considered for interpreting the Lonar samples: 42 Degree of anisotropy (P / ) = exp [2*Σ (ln K i /K) 2 ] 1/2 where i= 1 to 3, and the 43 Shape parameter (T) = [(2*ln K 2 - ln K 1 - ln K 3 )/(ln K 1 - ln K 3 )], where exp and ln means exponential and natural logarithm respectively; K 1, K 2 and K 3 are the maximum, intermediate and minimum susceptibility axes, and 46 K (mean susceptibility) = (K 1 + K 2 + K 3 )/ Additionally, a parameter called degree of anisotropy (A) that quantified the departure from the isotropic case (when all three principal susceptibilities are equal) (after Cañón-Tapia et al., 1997) was also used for our samples for further comparison, where A= 100 *{1-[(K 3 +K 2 )/2K 1 ]} and A ranges between 0% (isotropic) to 100% (K 1 >> K 2 and K 3 ). 2

3 52 Figure captions in GSA data repository Figure GSA DR-1 (a) Ejecta profile at Kalapani dam area at the SW of the Lonar crater. Soil horizon formed by erosion of ejecta at higher altitude [S] forms a cap on the distant ejecta [E] resting over paleosol [P]; chisel marking the boundary between top soil layer and ejecta cover; hammer head indicates the boundary between ejecta cover and underlying paleosol. The boundary between ejecta and underlying paleosol is less distinct due to CaCO 3 veins leached from the ejecta cap during weathering. The height of exposure is ~1.6 m. (b) Sub-horizontal basalt flows at ~2 km ESE of the Lonar crater at Durga Tegri area showing semicontinuous flow-parallel fractures (shown by horizontal arrows) and less-common sub-vertical fractures (shown by vertical arrows pointing downward) in cross-section; total thickness of exposure is ~3.5 m. (c) Plan view of an exposure of shocked basalt on crater rim at SSE sector showing fracture cleavage; the attitude of cleavage is shown by a symbol, which dips towards the crater depression (note arrow). (d) Plan view of basalt on crater rim at the SSW sector showing a set of widely spaced fractures, arrow indicates direction of dip of fractures towards the crater depression; scale- hammer with length ~39 cm. (e) Cross-sectional view of a remnant basalt flow in the WSW sector showing overturned dip; hammer (~39 cm) showing attitude of flows; black arrow points to crater depression. (f) Basalt flow with flow-parallel cleavage at the WNW sector showing overturned dip (crosssectional view); hammer is placed parallel to flow; arrow points to the crater depression. (g) Cross-sectional view of the ejecta at the north of the Lonar crater. Note an angular piece of shocked basalt within ejecta showing development of strong fracture cleavage due to impact (double-headed arrow shows trend of fracture). Hammer head indicates bottom of the section. (h) A piece of maskelynite from within ejecta showing development of a strong fracture cleavage (P) and a secondary weak cleavage (S) in cross section; coin (1.8 cm) scale. 3

4 Figure GSA DR-2 Orientations of basalt flows (solid Gray Square) and fracture cleavage (open square) occurring on rim of the Lonar crater in the lower hemisphere of the π-pole diagram. For details see text Figure GSA DR-3 P / -T plots for unshocked and shocked basalts from around the Lonar crater (for sample locations see figure 1d). Note the higher P / value and oblate shape of susceptibility ellipsoid are the characteristics of unshocked target basalts (a), whereas the shocked basalts have restricted and lower P / values with the variation of shape of susceptibility ellipsoid from oblate to prolate (b-i). 89 Relationship between P / and A parameters (Cañón-Tapia et al., 1997) is shown in (j); abbreviations: DT: target basalt samples from Durga Tegri, CR-E: samples from the eastern crater rim sector, CR-rest: samples from rest of the crater rim, Khini: samples from Khini village Figure GSA DR-4 The lower hemisphere stereographic projections of AMS susceptibility axes (symbols as in figure 3) and P / -T plots of shocked basalts from the eastern cross-section of the Lonar crater below the rest house. Note relatively clustering of AMS susceptibility axes for basalts from higher altitude (~560 m) and distribution of K 2 and K 3 susceptibility axes of basalts from lower altitude (~ m) on a NW-SE vertical plane

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6 Figure GSA DR-2

7 Figure GSA DR-3

8 ~ m ~560 m ~520 m ~494 m Completely weathered basalt Lake water level Figure GSA DR-4