Geology of Lonar Crater, India

Abstract

Lonar Crater, India, is one of the youngest and best preserved impact structures on Earth. The 1.88-km-diameter simple crater formed entirely within the Deccan traps, making it a useful analogue for small craters on the basaltic surfaces of the other terrestrial planets and the Moon. In this study, we present a meter-scale-resolution digital elevation model, geological map of Lonar Crater and the surrounding area, and radiocarbon ages for histosols beneath the distal ejecta. Impact-related deformation of the target rock consists of upturned basalt fl ows in the upper crater walls and recumbent folding around rim concentric, subhorizontal, noncylindrical fold axes at the crater rim. The rim-fold hinge is preserved around 10%-15% of the crater. Although tearing in the rim-fold is inferred from fi eld and paleomagnetic observations, no tear faults are identifi ed, indicating that large displacements in the crater walls are not characteristic of small craters in basalt. One signifi cant normal fault structure is observed in the crater wall that offsets slightly older layer-parallel slip faults. There is little fl uvial erosion of the continuous ejecta blanket. Portions of the ejecta blanket are overlain by aerodynamically and rotationally sculpted glassy impact spherules, in particular in the eastern and western rim, as well as in the depression north of the crater known as Little Lonar. The emplacement of the continuous ejecta blanket can be likened to a radial groundhugging debris fl ow, based on the preserved thickness distribution of the ejecta, the efficient exchange of clasts between the ejecta fl ow and the underlying histosol, and the lack of sorting and stratifi cation in the bulk of the ejecta. The ejecta profi le is thickened at the distal edge and similar to fl uidized ejecta structures observed on Mars.

Impact ejecta emplacement on terrestrial planets

“…6B). This is consistent with observations at the similarly-sized 23-km-diameter Haughton structure, Canada , and the smaller simple 1.2-km-diameter Barringer (Grant and Schultz, 1993) (USA) and 1.8-km-diameter Lonar (Maloof et al, 2010) (India) craters (Table 1). The sharp contact between the Ries ejecta layers (Fig.…”

“…No breccia deposits, which could represent ballistic ejecta, have been recognized at either Tenoumer or Pingualuit. At the Lonar and Barringer Craters, impact melt-bearing breccias have been identified in the ejecta deposits (Maloof et al, 2010;Osinski et al, 2006), but no impact melt rocks to date.…”

“…The pale gray impact melt rocks are derived from deeper levels. Bs Continuous ballistic ejecta blanket; evidence for ground hugging flow following ballistic emplacement (Maloof et al, 2010). Possibly at the transition of "simple ballistic emplacement and ballistic sedimentation" (Maloof et al, 2010).…”

“…Bs Continuous ballistic ejecta blanket; evidence for ground hugging flow following ballistic emplacement (Maloof et al, 2010). Possibly at the transition of "simple ballistic emplacement and ballistic sedimentation" (Maloof et al, 2010). Impact spherules are found in many locations with rarer larger samples of melt-bearing rocks.…”

Microbiology of Lonar Lake and other soda lakes

“…Lonar crater (19159 0 N, 76131 0 E) is a simple, bowlshaped, near-circular and remarkably well-preserved depression in the otherwise featureless Deccan Plateau in Buldhana district, Maharashtra state, India (Fredriksson et al, 1973;Maloof et al, 2010). The crater is 1.88±0.05 km wide and approximately 135 m deep, with the rim of the crater rising 30 m above the surrounding plains.…”