The reasons for dark patches on sediments related to decay at still water, burrow canals, and vertical carrier flows

At the sediment surfaces, the detection of dark patch-type color changes is very easy which are mostly related to Carbon, Hydrogen Sulfur, and Iron-Sulfur conversion diffusions. After the decay of settled animal and Plant remains interact with its sitting clay during sedimentation at still waters. Some of decomposing remnant particules move away  such as mostly  chitin (long fragmentation time and ligthweigth ) with drifter currents time by time available. Dark patches are visible as horizontal centimeter scale to a vertical depth of a few mm. Dispersion of the dark color is limited with result of diffused materials as nutrient and consumed oxygen from clastics or oxides by microorganism populations (increse and decrease of population) . Second type  dark patch generations are possible around bioturbation traces at sediments such as a burrow or canal-type gaps by living worms or burrowed larvas (water - clay tank experiment). Daily physical frictional movements of larvae helped to anoxic suspension displacements at depth of housing gaps to the sediment surface (at the water - clay experiment and its sediment layer setup sequence is oxic layer on top and anoxic clay layer at the bottom).

Regional anoxia of  bacteries as remnant of host is possible after larval displacement from the vertical canal.   In the low oxygen water sediment tank experiment we observed first and second type dark patch generations. In our oil covered oxygen isolated high anoxia experiment with flies and ants, the first type of dark patches in anoxia conditions was generated and as result especially insects provided well dark patches without any insitu remnants because chitin parts slowly drifted. (chitin solubility or fragmentation time very long with complex biological processes at salty water and oil  and fast with acetic acid). The observation was experienced with randomly natural falls of flies and wingy ants into the experiment fluids. Type 3, texture type dark patch dispersions at sediment cores associated to microorganism life in sediment clay. The initial stages of dark color patches at the clay layer were more visible after increasing  temperature and decreasing pressure of the environment around growing pressure gap of hydrogen sulfur gas after the stop of diffused oxygen support with pore water displacement. Developing stages of the third type; tubular form micro mud volcano type dark patch structures occurred at the water-sediment tank experiment. All type  patch is very important for micro XRF measurements because actual element readings change by carbon and other enriched contents, especially non-oxidized carbon's high energy X-ray beam suppression. For high precise measurements such as providing micro XRF elemental data or climate , paleo-environment interpretation, you need to choose parallel measurement way without dark patches because inorganic sediment material-based information gets the wrong clues.