Fig. 7. Cyclades Macula

Cyclades Macula is a dark, rhomboidal band bridging a gap between en echelon segments of the south polar strike-slip fault, Astypalaea Linea (Tufts, 1996; Tufts, 1998; Tufts et al., 1998c). Most of it can be seen here in 42 m/pixel Galileo images (E17 orbit). The band trends northeast, is approximately 47 km wide, measured parallel to the fault, and it spans a 47 km separation between fault segments. The prominent ridge crossing the band is 2.5 km wide. Cyclades Macula has a low, flat, striated surface that is interrupted by more recent ridges or by subareas where striations are slightly elevated. The probable active structure was a barely-visible thin crack that takes a rounded stairstepping path diagonally across the rhomboid between its SW and NE corners (connecting with master strike-slip faults there). Internal striations are subparallel to this structure; they are especially prominent where the "active" structure is most orthogonal to the relative motion of Astypalaea Linea. However, a strong bilateral symmetry is not apparent amidst this subparallel pattern. (Such symmetry is apparent along en echelon pull-aparts which compose the fault zone farther south.) Reconstruction of the fault, including Cyclades Macula, demonstrates that Cyclades Macula is dilational. It is similar to a "pull-apart," a type of tensional feature common in terrestrial strike-slip fault zones.