Molasse

molasse [mə′läs]

(geology)

A paralic sedimentary facies consisting mainly of shale, subgraywacke sandstone, and conglomerate; it is more clastic and less rhythmic than the preceding flysch and is generally postorogenic.

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Molasse 

a complex of rocks that forms under mountain relief conditions and is made up of thick layers (up to several thousand meters) of terrigenous rocks: conglomerates, sandstones, siltstones, and clays (sometimes with bands of limestone and marl). The formation of molasses corresponds in time to the fold-forming and mountain-building stage in geosynclinal systems and is physically associated with the foredeeps and intermontane troughs that accompany developing mountain structures. Many geologists believe that molasses express a special orogenic stage in the development of folded systems when the geosynclinal stage proper has already concluded.

A distinction is made between lower molasses (schlieren) and upper, or coarse, molasses. These two forms characterize the substages of mountain building. Lower molasses usually occur as the sediments of shallow basins that surround the branching interior uplifts of geosynclinal systems; they are represented by sandstones, siltstones, and clays and frequently contain interlayers of limestone and marl (for example, the Oligocene and Lower Miocene of the Caucasus). Upper molasses are composed of detritus worn from rapidly weathered mountain ranges that had emerged in the preceding substage. They are made up of conglomerates, breccias, sandstones, and clays and form thick layers that accumulate under continental conditions (for example, the Pliocene of the Caucasus). Deposits of coal, petroleum, gas, cuprous sandstones, salts, and other mineral products are associated with molasses.

V. A. GROSSGEIM