الملخص

Travertine deposits occur in Wadi Garmawa about (3) km northeast Dohuk city in adistinct cave and adjacent areas above exposed carbonate rocks of Shiranish Formation (Late Campanian - Maastrichtain). These deposits are divided according to their field location into hypogean and epigean travertine . Hypogean travertine occurs inside the cave as a variety of carbonate cave deposits (Speleothems) associated with distinct karstic features including high porous tufa , massive or thin laminated travertine and moonmilk deposits occurring at different sites; and were formed by seepage of surface water, bacterial activity, seasonal alteration and chemical weathering alternatively. While the epigean travertine is found along the outcoming water stream either laminated or massive travertine pools and dams alternatively and repeatedly. Both laminated and massive epigean travertine are produced from coating the algae with calcium carbonate at the water stream due to the process of photosynthesis by algae. Most of travertine deposits in the study area are associated with the released sulphur which is thought to be formed predominantly by the oxidization of H2S in the presence of oxygen and/or bacterial activity in the presence of light.