Kodi kuyenda kwa turbidity mu sedimentology ndi chiyani?
Mu sedimentology, njira imodzi yofunika kwambiri yomvetsetsa kupangika kwa malo okhala m'nyanja yakuya ndi mafunde a turbidity. Mafunde amenewa, omwe nthawi zambiri amatchedwa "sediment mass flows," amatsika m'malo otsetsereka a pansi pa nyanja chifukwa cha mphamvu yokoka. Ngakhale kuti amapezeka pansi pa nthaka, njirayi ingafanane ndi "mtambo wa matope" womwe umadutsa mofulumira pansi pa nyanja, kunyamula tinthu ta matope kuchokera kumadera osaya kupita ku mabowo akuya. Kumvetsetsa mafunde a turbidity kumathandiza akatswiri a za nthaka kutanthauzira mbiri ya malo osungiramo zinthu, kujambula zoopsa zomwe zingachitike pansi pa madzi, komanso kuwunikanso kupangika kwa malo osungiramo madzi a hydrocarbon.
Kumvetsetsa kayendedwe ka madzi
Madzi oundana ndi madzi oyenda (nthawi zambiri madzi a m'nyanja) omwe amakhala ndi madzi oundana chifukwa cha kuchuluka kwa matope omangika (mchenga, matope, dongo). Kusakaniza kwa madzi ndi matope kumeneku kumakhala ndi kuchuluka kwakukulu kuposa madzi ozungulira, kotero kumayenda motsatira njira yolowera pansi pa nyanja ndikutsika. Pamene madzi akuyenda, matope amatha kukhalabe omangika chifukwa cha kugwedezeka kwamkati; komabe, pamene mphamvu ya madzi ikuchepa, matopewo adzakhazikika ndikupanga zigawo zomwe zimadziwika kuti turbidite deposits.
Mosiyana ndi mafunde wamba a mitsinje, omwe amayendetsedwa makamaka ndi ma gradients pamwamba, mafunde a turbidity amayendetsedwa ndi kusiyana kwa kuchulukana ndi mphamvu yokoka. Chifukwa chake, amagawidwa ngati mafunde a density, omwe amadziwika ndi kuthekera kwawo kuyenda mtunda wautali kudutsa pansi pa nyanja zakuzama.
Kodi mafunde a turbidity amapangidwa bwanji?
Mafunde a turbidity nthawi zambiri amayamba chifukwa cha zinthu zomwe zimasokoneza dothi lomwe lili pamtunda wa kontinenti kapena m'mphepete mwa shelufu ya kontinenti. Zina mwa zinthu zomwe zimayambitsa vutoli ndi izi:
1. Kugumuka kwa nthaka ya pansi pa nyanja ndi kugwa kwa mathithi
Dothi losungunuka m'malo otsetsereka limatha kulephera (kulephera kwa mtunda) chifukwa cha katundu wambiri, zivomezi, kapena kusintha kwa kuthamanga kwa madzi m'mabowo. Zinthu zomwe zikugwa zimatha kusintha kukhala madzi ochulukirapo komanso osinthasintha.
2. Chivomerezi
Kugwedezeka kungasokoneze kukhazikika kwa matope ndi kuyambitsa kutulutsidwa kwa zinthu zopachikidwa, zomwe zimapangitsa kuti mafunde akuluakulu komanso othamanga a matope azitha kugwedezeka.
3. Kusefukira kwakukulu kuchokera ku nthaka (kutuluka kwa hyperpycnal)
Pazifukwa zina, madzi a m'mitsinje omwe ali ndi matope ambiri amatha kukhala ndi kuchuluka kwakukulu kuposa madzi a m'nyanja, kotero "amamira" ndikuyenda ngati madzi ochulukirapo m'nyanja yakuya.
4. Mphepo yamkuntho ndi mafunde amphamvu
Pa mashelufu osaya kwambiri, mphepo yamkuntho imatha kuyambitsa matope ndikutumiza kumphepete mwa mashelufu, komwe imagwera pansi pa phirilo ndikuyambitsa mafunde amadzi.
5. Kuphulika kwa mapiri ndi pyroclastic kumapita m'nyanja
Zinthu zophulika zomwe zimalowa m'nyanja zimatha kusakanikirana ndi madzi ndikupanga kuchuluka kwa matope.
Mwachidule, mafunde a matope amapezeka pamene pali madzi oundana komanso zinthu zomwe zimathandiza kuti madzi oundana asunthe pansi ndi mphamvu zokwanira.
Njira yoyendetsera ndi kayendedwe ka kayendedwe kake
Mafunde amadzimadzi amayenda ngati "mtambo" wa matope, nthawi zambiri amakhala okhuthala pansi ndi ocheperapo pamwamba. Liwiro la madzi limasiyana—kuyambira pang'onopang'ono mpaka mofulumira kwambiri—kutengera kuchuluka kwa matope, kutsetsereka kwa nthaka, ndi kuchuluka kwa matope. Nthawi zambiri, madzimadzi amenewa amatha kuyenda makilomita makumi ambiri kuchokera komwe akuchokera, kutsatira maphompho a pansi pa nyanja kenako n’kufalikira kunja kuti apange fan ya pansi pa nyanja.
Mwachidule, machitidwe a turbidity nthawi zambiri amagawidwa m'magawo angapo:
– Malo oyambira/kukokoloka kwa nthaka: malo otsetsereka kumene dothi limatulutsidwa ndipo madzi amayamba kutuluka; nthawi zambiri komwe kukokoloka kwa nthaka kwamphamvu kumachitika.
– Malo oyendera: madzi amalowa mu ngalande ndipo amatha kunyamula mchenga.
– Malo otayira zinyalala: mphamvu zimachepa, njira zimatha kukulirakulira kapena kutha, zinyalala zimayikidwa kuti zipange tinthu tating'onoting'ono ndi mapepala amchenga.
Kusintha kwa mphamvu ya kayendedwe ka madzi kumawongoleranso kukula kwa tirigu wonyamulidwa. Pamene mphamvu ikuchepa, tirigu wokhuthala (mchenga) umakhazikika kaye, kutsatiridwa ndi matope ndi dongo. Njira imeneyi imapanga mabedi okonzedwa bwino omwe ndi khalidwe lakale la turbidites.
Malo osungiramo ma turbidite ndi ndondomeko ya Bouma
Chinthu chachikulu chomwe chimapangitsa kuti madzi aziyenda bwino ndi ma turbidite deposits, omwe amadziwika ndi kapangidwe kake ka sedimentary ndi ma pattern a ma bedi. Chimodzi mwa zitsanzo zodziwika bwino pofotokoza kapangidwe ka mkati mwa ma turbidites ndi Bouma Sequence, makamaka pa ma turbidites a "classic" ochokera ku mchenga kupita ku silt. Mwachidule, sequence iyi ikufotokoza kusintha kuchokera ku mphamvu yayikulu kupita ku yochepa mkati mwa chochitika chimodzi chokhazikika:
– Ta: mchenga waukulu kapena mchenga wabwinobwino (wokhala ndi mawanga ozungulira pansi, wopyapyala pamwamba) chifukwa cha kusungunuka kwa madzi mwachangu.
– Tb: kupendekera kwa madzi kofanana, kusonyeza kuti kuyenda kwa madzi kwayamba kukhala kokhazikika.
– Tc: ripple cross-lamination, mphamvu imachepa.
– Td: kupukuta bwino pa matope.
– Te: dongo/chonyowa cha hemipelagic chomwe chimakhazikika pang'onopang'ono pambuyo pa vuto la madontho.
Si ma turbidite onse omwe amasonyeza dongosolo lonse la Ta-Te. Ma depositi ambiri amangowonetsa magawo ochepa, kutengera momwe madzi amayendera, kupezeka kwa matope, ndi njira zomwe zagwiritsidwa ntchito pambuyo poika madzi.
Malo okhala ndi sedimentary okhudzana ndi kuyenda kwa madzi
Mafunde ofala kwambiri a turbidity amapezeka mu:
- Kutsetsereka kwa kontinenti ndi kukwera kwa kontinenti
Malo okhala ndi malo otsetsereka okwanira kuyendetsa mafunde ochulukirachulukira.
- Ma canyon a pansi pamadzi
Imagwira ntchito ngati "njira" yomwe imayang'ana kayendedwe ka zinthu.
- Mafani a sitima zapamadzi
Dongosolo lalikulu, looneka ngati fani m'nyanja yakuya, nthawi zambiri limakhala ndi ma channel-levees ndi lobes.
- Mabowo akuya kwambiri m'nyanja
Ndi malo osonkhanira ma turbidites abwino, makamaka mbali yakutali.
M'mabowo ambiri, ma turbidite amamanga miyala yolimba yomwe imalemba mbiri ya dziko lapansi, kupezeka kwa matope kuchokera kumtunda, komanso kusinthasintha kwa madzi a m'nyanja.
N’chifukwa chiyani kuyenda kwa madzi m’nthaka n’kofunika?
1. Chinsinsi chokonzanso mbiri yakale ya nthaka
Ma turbidite amalemba zochitika zina: kugwa kwa nthaka, zivomerezi, kapena kusefukira kwa madzi kwakukulu. Mwa kuphunzira momwe amagawikira ndi kufalikira kwawo, akatswiri a za nthaka amatha kutanthauzira momwe madzi amayendera komanso kusintha kwa malo okhala ndi nthaka pakapita nthawi.
2. Zofunika pa kufufuza mafuta ndi gasi
Malo ambiri osungiramo madzi a hydrocarbon amapezeka m'miyala yamchenga ya turbidite, makamaka m'mafano a pansi pa nyanja. Miyala yamchenga ya turbidite imatha kukhala ndi ma porosity abwino komanso kulowa bwino, ngakhale kusiyana kwawo mkati kumafuna kuyeserera mosamala.
3. Zimathandiza kumvetsetsa zoopsa za nthaka ya pansi pa madzi
Kuyenda kwa dothi kungawononge zomangamanga monga zingwe zolumikizirana ndi sitima zapamadzi ndi mapaipi. Kumvetsetsa njira ndi zomwe zingachitike chifukwa cha dothi ndi kothandiza pochepetsa zoopsa.
4. Chofunika kwambiri pa maphunziro a paleoseismological
M'madera ena, zigawo za turbidite zimatha kulumikizidwa ndi zivomerezi zazikulu zakale. Izi zimapangitsa kuti turbidites ikhale "yosungira" yachilengedwe yophunzirira kuchuluka kwa zivomerezi m'malo ocheperako.
Momwe mungazindikire ma turbidites m'munda kapena pakati pa kubowola
Katswiri wa zamadzimadzi nthawi zambiri amazindikira ma turbidites kudzera mu kuphatikiza kwa makhalidwe otsatirawa:
– Gawo lokhazikika bwino (kukula kwa tinthu tating'onoting'ono kupita mmwamba).
– Kapangidwe ka Bouma laminate (kagawo kapena kokwanira).
– Kukhudza kwa basal kumakokoloka ndipo nthawi zina kumakhala ndi zizindikiro zapansi pa nthaka (monga flute casts) zomwe zimathandiza kudziwa komwe mafunde a paleocurrents akupita.
- Kubwerezabwereza kwa ma phukusi otsatizana omwe akuwonetsa zochitika za nthawi zina (malo ochitira zochitika).
- Kusintha kwa mbali kuchokera ku malo osungira njira (okhuthala komanso okhwima) kupita ku malo osungiramo zinthu (oonda komanso ofewa).
Kusanthula kukula kwa tirigu, petrography, ndi deta ya geophysical (monga seismic) nthawi zambiri zimagwiritsidwa ntchito pojambula mawonekedwe a mchenga wa turbidite pa sikelo ya beseni.
Kutseka
Mafunde a turbidity ndi mafunde odzaza ndi sediment omwe amayenda pansi pamadzi chifukwa cha kusiyana kwa kuchulukana ndi mphamvu yokoka. Njirayi imapanga malo osungira turbidite, omwe ali ndi zigawo zosiyana, zomwe nthawi zambiri zimatchedwa Bouma Sequence. Mu sedimentology, mafunde a turbidity ndi ofunikira chifukwa amalamulira mayendedwe a sediment kupita ku nyanja yakuya, amapanga mafani a pansi pamadzi, ndikusunga zambiri zokhudza zochitika zakale za geological. Kuphatikiza apo, kumvetsetsa turbidity kumakhalanso ndi tanthauzo lothandiza pakufufuza zinthu komanso kuchepetsa zoopsa za zomangamanga za pansi pa madzi. Mwa kuphunzira turbidites, kwenikweni timawerenga "mbiri ya zochitika" zomwe zachitika pansi pa nyanja ndikupanga malo a sedimentary omwe tikukumana nawo lero.
