AbstractTo investigate a possible physical association between the Southern Coalsack and the Chamaeleon-Musca (SCCM) dark clouds we have obtaineduubyβphotometry for 1017 stars covering the connecting area: 308° ≥l≥ 294° and –20° ≤b≤ 5°. Analysis of the various colour excessE(b–y) vs. distance diagrams has indicated the presence of a local low absorption volume limited at 150 ± 30 pc from the Sun by an extended interstellar dust sheet-like feature, that is followed by a region where almost no

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... itional reddening is measured for the next 350 pc. Combined with other data on the local ISM the existence of the dust sheet at an identical distance of the SCCM dark clouds have suggested that these clouds could be higher density regions associated to the diffuse lane of dust of the Local-Loop I bubbles' interface.