Davrai Ordovik

Ordovik, davrai (siste­mai) ordovik, davrai duyumi erai paleozoy bad az kembriy. Bo usuli radiologi muayyan shudaast, ki Ordovik 500 million sol muqaddam ogoz yofta, 60 million sol davom kardaast. Tahnishasthoi in davra boshand, si­stemai Ordovikro tashkil medihand. Sis­temam Ordovikro soli 1879 geologi anglis Ch. Lapuors dar Uels muqarrar namud.

Nomi Ordovik az nomi qabilai qadimi ordovikhoi Angliya barmeoyad. Soli 1960 sessiyai 21-umi Kongressi baynalkhalqii geologho O.rdovikro hamchun davrai mustaqil etirof kard. Am­mo to in vaqt Ordovik zamoni avvali davrai silur hisob karda meshud. Dav­rai Ordovikro ba zamonhoi avval, miyona, okhir va sistemai onro ba qismhoi poyon, miyona va bolo taqsim meku­nand.

Barobari sarshavii davrai Ordovik qitahoi kaloni khushkiqoi rui Za­mni (Evropai Garby, atrofi bahri Bal­tika, Ural, Qazoqistonu Osiyoi Mi­yona, qismi ziyodi Sibir, Osiyoi Janubi Sharqi, nimai sharqii Avstra­liya, qarib tamomi Amerikin Shimoli, qisman Amerikai Janubi va Afrika) furu nishasta, zeri obi bahr mondand. Dar miyonahoi davrai Ordovik transgressiyai bahrho ba avji aloi khud rasid. Dar okhirhoi dav­rai Ordovik az zuhur yoftani fazai purzuri chindorshavii kaledony masohati bahrho khele mahdud gardida, qitahoi kalonu navi khushki paydo shudand.

Bahrhoi davrai Ordovikro ba 2 tip judo mekunand: platformag i — tahshinhoyashon asosan karbo­nati va geosinklinali — tah- shinhoyashon beshtar terrigeni (regu shagal, loyqa va gayra) va vulqoni (mahsuli otashfishonihoi zeriobi). Okhirhoi davra yak qator nohiyaho — Appalachi, Uels, Sibiri Garbiyu Sharqi, Qazoqiston ba markazhoi kaloni vulqonizm tabdil yoftand.

Az olami hayvonoti davrai Ordovik besh­tar hayvonhoi bemuhrai bahri (brakhiopodaho, trilobitho, narbadanoni sarpo, graptolitho, suzanpuston) inkishof yofta budand. Dar okhirhoi davra mshankayu marjonhoi bahri va avvalin hayvonhoi khushkigard — kajdumu hazorpoyho paydo shudand. Florai Ordovik asosan az bakteriyahoi gunogun, Obsabzho va psilofitho iborat bud.

Az tahnishastu jinshoi intruzivii davrai Ordovik konhoi neft, varaqsanghoi suzanda, fosforit, madanhoi ohan, mangan, tillo va digar metallho yoft shudand.

Dar territoriyai Tojikiston tahnishasthoi sistemai Ordovik beshtar dar nohiyahoi qismi shimoli, markazi va janubi sharqii respublika duchor meoyand, ki dar in joyho jinshoi erai pale­ozoy farovonand.

Qarib dar hamai in nohiyaho tahnishasthoi sistemai Ordovik az qabathoi regsakgu varaqsanghoi gili va fillitho, ki bazan qabathoi tunuki ohaksangu marmar niz dorand, tarkib yoftaand. Gafsii tabaqai tahvishastho ba yakchand sad metr merasad. Az boqimondai hayvonhoi bahri va tarkibi litologii tahnishastho malum meshavad, ki hanuz dar davrai Ordovik dar territoriyai Tojikistoni imruza havzahoi kaloni bahrhoi na chandon chuqur vujud doshtand.