Two different reds! - sorry, I should have said this last time you posted, but I was in Indonesia then.

"Filled" = "filled craters"! (there might be a small volcano just top left of centre at 3.80E 4.40N)

Extract from the Hynek paper:

"However, there is a distinct lack of any sizeable volcanic constructs in the TM region. We consider three broad categories of volcanic deposits – lava flows, ignimbrites, and air fall – and test their compatibility with the morphology, bedding characteristics, thickness and areal extent, erosional nature, and possible source region of the hematite and associated deposits."

"The primary argument against a volcanic origin of martian hematite is a lack of nearby sources HYNEK ET AL.: GEOLOGIC SETTING AND ORIGIN OF TERRA MERIDIANI HEMATITE DEPOSIT ON MARS 20 [Christensen et al., 2000, 2001]. Theoretical arguments indicate that the reduced gravity and atmospheric drag on Mars should result in a broad distribution of pyroclastic materials; much more so than on Earth [Wilson and Head, 1981a, 1981b, 1994; Hynek et al., 2002]"

"[Malin and Edgett, 2000]. Hynek et al. [2002] used MOC and MOLA data to test the hypothesis that these materials may be genetically linked to one or more source regions. The workers found that these deposits are morphologically similar to pyroclastics and that there is a general thickening of deposits in the direction of the Tharsis region. These observations led them to hypothesize that the friable layered deposits that host the hematite could be remnants of a large-scale ash cone from repetitive explosive eruptions in the Tharsis region. We conclude it is plausible that the friable layered equatorial deposits could have come from explosive eruptions of distal volcanoes."

"Mapping relations and crater counts reveal that the TM deposits likely formed in the Late Noachian to Early Hesperian time period of Mars, although a precise age is impossible given the history of burial and exhumation. The origin of the layered materials is probably volcanic, in the form of ash falls and/or flows, although some of the lower layers exhibit possible effusive lava flow features. No major volcanic constructs have been identified in TM although source regions may remain buried. If the material is volcanic air fall, the source(s) may be several thousand kilometers away [Hynek et al., 2002]."