Quaternary travertine ridges in the Lake Urmia area: active extension in NW Iran

The Lake Urmia area is surrounded by several major active oblique-slip faults with dextral and normal offsets. Extensive travertine ridges were produced along the E-W up to NW-SE trending extension fractures in the Lake Urmia area, NW Iran. These fractures are parallel to subparallel with abundant normal faults. Pliocene-Quaternary volcanic domes occur in the area and their activities tend toward apparent distinction between colored travertine layers and ridges. Two different modes of banded travertine within the fissures and layered travertine on the surface are observed. Some banded travertines are not vertical and obviously were tilted. Layered travertines were cut, rotated, and displaced sequentially by NW-SE oriented normal faults. Local collapsed areas are produced subparallel to the extension fractures, implying that extension in the area has continued to recent time. We conclude that extensive deposition of travertine is produced along extension fractures with volcanic activity and active oblique-slip normal faults indicating regional extension in the Lake Urmia area. The Lake Urmia area in NW Iran is not only situated in an active tectonic region in junction with Anatolia, escaping to the west, and the Iranian microcontinent, escaping to southeast along the major strike-slip faults, but it is also located at the extension termination of the Main Recent Fault.