*Abnormal Ophiolite (Olivine/Pyroxene Rich) Sandstone NE Iraq: An Approach to the Origin… DOI: http://dx.doi.org/10.5772/intechopen.108333*

the sediment is performed by gravity flows and/or turbidity currents as a result of migrated active channel floor [20, 30–32]. Debrites and developed turbidites comprise two stages of the sediment-gravity-flows. The debris flows of muddy pebbly sandstone are represented by suites of facies F4, F5, F6, F8, F9, and F10. The coarse grains and gravel are supported by a cohesive matrix of interstitial fluid and mud [20]. Sand and mud turbidites are deposited from suspended loads and graded upwards by fluid turbulence in the inner channel and on levee. Channel sediments commonly deposited the following facies, represent a spectrum of submarine mass-movement processes [20, 33–39].


#### *6.1.2 FA2, inner fan/channel levee*

The sandstone/mudstone beds are arranged in turbidity Bouma cycles with or without basal division (Ta). The thickness of these beds ranges from 0.5 m for sandstones and 1.5 m for mudstones. Balls and pillows, disturbed beds, convolute beds, slump and slide beds, load, and scour and grooved surfaces are the main characteristic sedimentary structures.

Slump and/or slide of interbedded sandstone/mudstone horizons on both sides of the channel valley are filled and interfinger with channel and interchannel deposits that are interpreted here as levee/inner fan deposits cf. F2, F3, F4, F5, F7. Deformation of the slump is represented by recumbent folded horizons bounded by undeformed beds. The sandstone's and mudstone's balls and pillows are associated with slumping and/or sliding strata, and some are very large with a diameter of about 1 m.

#### *6.1.3 FA3, outer fan*

The outer fan deposits consist of thick mudstone/shale beds interbedded with very thin sandstone horizons graded upwards to reveal Bouma cycles without the basal divisions (Ta, Tb). The outer fan succession comprises a developed thick sequence of alternating non-channelized sandstone bodies and associated thin/thick bedded argillaceous mud sediments cf. F1, F2, F3, F5, F7, F11.

The middle part of the Kolosh succession cf. 45–90 m above the lower base permits detailed inspection of numerous thickening upward cycles. Each cycle consists of lower thin-bedded and fine-sandstone facies, transitionally overlain by thicker bedded/massive mudstones. These criteria and terminology are already discussed by Refs. [30, 31, 40, 41], which are interpreted as lobe-fringe and lobe-fan deposits, respectively. These two facies' cycles are either symmetric or asymmetric, thus reflecting sudden or gradual shifting of the related feeder system as suggested by Refs. [20, 41].

Typical sedimentological features of thin-bedded lobe-fringe deposits are included cyclic vertical variations depicted by changes in the sand/shale ratio and in the sandstone bed thickness.

The lobe-fringe turbidite beds displayed base-missing of Bouma sequences, that is, Ta, Tb, and/or Tc. Typically, by far, the Tc-e subdivisions are predominant. In part, Tb-e cycles are displayed unusual thick beds, which are randomly scattered in the succession. The sandy beds' division, which includes current-ripples is bounded by upper surface gradational with the overlying turbiditic mudstone.

The post-depositional and/or syndepositional plastic deformation and liquefaction are the causes of abundant convolute, slump, balls, pillows, and the small-scale features, such as pseudo-nodules observed, in the sandy and muddy portions of many beds. Occasionally thin veneers of bioturbated hemipelagic mudstone and/or lime mudstone are found at the top of some turbidity cycles.
