Fluid-induced interfacial deformation structures (FIDS) are common in turbidite successions where they form in soft, cohesive substrates beneath sediment gravity flows, but their significance has only recently been recognised. Their range of forms and sizes encompasses most of the morphological types attributed to microbiallyinduced sedimentary structures (MISS) and the two have likely been conflated. Variants of FIDS include longitudinal ridges and furrows identical to the linear wrinkle marks assigned to MISS, and polygonal networks, a common form of MISS, together with polygonal and mamillated forms that have both MISS and FIDS representatives.
Even the distinctive MISS form Kinneyia, is also found within the FIDS spectrum. Some FIDS may have also been assigned to Ediacaran taxa. Environmental context is important when distinguishing FIDS from MISS. Intertidal MISS occurrences are unlikely to be FIDS because the sediment gravity flows that produce the latter are unlikely to be found in such settings. However, MISS encountered in turbidite settings are likely to be FIDS. One of the few distinctions between MISS and FIDS occurs when textured surfaces are developed on the upper surfaces of sandstone beds and they are overlain by fine-grained sediments; in this case a microbial origin is likely.