Ruwa da aka gano

Wani tashar kogin da aka tono shi ne dutsen yashi wanda ya kasance lokacin da ambaliyar ruwa mai laushi ta lalace. Shirin ya fara ne tare da zubar da yashi a cikin tashar kogi (yawanci kogi mai laushi) da sauka a kan ambaliyar da ke kusa. A ƙarshe an watsar da tashar kuma a tsawon lokaci ya zama an binne shi da ambaliyar ruwa daga wasu tashoshi. Saboda yashi yawo da ƙuƙwalwa (haɗin hatsi zuwa hatsi ya bar sarari tsakanin), ruwan ƙasa yana gudana cikin sauƙi ta cikin yashi fiye da ta cikin laka na ajiyar ambaliyar ruwa. 
Ma'adanai (yawanci calcium carbonate) na iya yin amfani da hatsi tare da canza yashi zuwa sandstone. A halin yanzu, matsin lamba daga turɓaya mai zurfi yana matse laka mai laushi yana canza shi zuwa laka. Miliyoyin shekaru bayan haka, rushewa na iya cire dutse mai laushi, wanda ba shi da ƙarfi kuma ya bar dutse mai tsayayya a matsayin tudun da ke da wuyar gaske. Don haka, hanyar kogi da aka gano wani nau'i ne na sauƙaƙewa: abin da ya kasance a baya ya fi girma yanzu, kuma akasin haka. Tashoshin da aka gano sune mahimman alamomi don jagorancin kwararar rafi na dā.

Wasu daga cikin misalai mafi kyau na tashoshin kogi da aka gano sun faru ne a cikin Ruby Ranch Member na Cretaceous Cedar Mountain Formation kudu maso yammacin Green River, Utah. A cikin Tsarin Dutsen Cedar a wannan ɓangaren Utah, sandstones na kogi da ke cika paleochannels a ciki an rufe su da calcium carbonate. Saboda wannan siminti, sandstone da ke cika waɗannan paleochannels sun fi tsayayya da rushewa fiye da shale da mudstone da ke kewaye da su. A sakamakon haka, lalacewar bambancin ya fi dacewa ya cire shale da mudstone kuma ya fallasa waɗannan hanyoyin tarihi a matsayin tuddai.Williams, R.M.E., T.C. Chidsey, Jr., and D.E. Eby, D.E., 2007, Exhumed paleochannels in central Utah - analogs for raised curvilinear features on Mars, in G.C. Willis M.D. Hylland, D.L. Clark, and T.C. Chidsey, Jr., eds., pp. 220-235, Central Utah - diverse geology of a dynamic landscape. Publication 36, Utah Geological Association, Salt Lake City, Utah.Harris, D.R. 1980. Exhumed paleochannels in the Lower Cretaceous Cedar Mountain Formation near Green River, Utah. Brigham Young University Geology Studies 27:51–66.

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