Olistostrome

Roadside cross-section of a large olistolith in the ophiolithic melange, Western Vardar Ophiolithic Unit of Serbia

The term olistostrome is derived from olio - a dish of many ingredients or stew; a mixture of heterogeneous elements; hodgepodge. and stroma - a bed covering (Greek equivalent of the Latin stratum). An olistostrome is a sedimentary deposit composed of a chaotic mass of heterogeneous material, such as blocks and mud, known as olistoliths, that accumulates as a semifluid body by submarine gravity sliding or slumping of the unconsolidated sediments. It is a mappable stratigraphic unit which lacks true bedding, but is intercalated amongst normal bedding sequences, as in the Tertiary basin of central Sicily.

Olistostromes are mélanges formed by gravitational sliding under water and accumulation of flow as a semi fluid body with no bedding.