Menene kwararar turbidity a cikin ilimin sedimentology?
A fannin nazarin halittu, ɗaya daga cikin muhimman hanyoyin fahimtar samuwar ma'adanai a cikin yanayin teku mai zurfi shine kwararar turbidity. Waɗannan kwararar, waɗanda galibi ake kira "kwararowar mass na laka," suna tafiya ƙasa da gangaren ƙarƙashin ruwa wanda nauyi ke motsa su. Kodayake suna faruwa a ƙarƙashin saman, ana iya kwatanta tsarin da "gajimare mai laka" wanda ke yawo cikin sauri a kan benen teku, yana ɗauke da ƙwayoyin laka daga ƙananan wurare zuwa zurfin kwano. Fahimtar kwararar turbidity yana taimaka wa masana kimiyyar ƙasa su fassara tarihin muhallin da aka ajiye, suna taswirar haɗarin ilimin ƙasa a ƙarƙashin ruwa, har ma da kimanta samuwar ma'ajiyar hydrocarbon.
Fahimtar kwararar turbidity
Ruwan turbidity wani ruwa ne mai gudana (yawanci ruwan teku) wanda ke da yawan turbidity saboda yawan laka da aka dakatar (yashi, laka, yumbu). Wannan cakuda ruwa da laka yana da yawa fiye da ruwan da ke kewaye, don haka yana bin yanayin ƙasan teku kuma yana motsawa ƙasa. Yayin da ruwan ke motsawa, laka na iya ci gaba da tsayawa saboda turbidity na ciki; duk da haka, yayin da kuzarin kwararar ke raguwa, laka zai kwanta kuma ya samar da yadudduka na musamman da aka sani da turbidite deposits.
Ba kamar yadda ake amfani da kwararar kogi na yau da kullun ba, waɗanda galibi ke gudana ta hanyar yanayin saman ƙasa, kwararar turbidity tana faruwa ne ta hanyar bambance-bambance a cikin yawan ruwa da ƙarfin nauyi. Saboda haka, ana rarraba su a matsayin kwararar ruwa mai yawa, wanda ke da alaƙa da ikonsu na tafiya mai nisa a ƙasan kwarin teku mai zurfi.
Ta yaya ake samar da kwararar ruwa mai turbidity?
Gabaɗaya, kwararar turbidity tana faruwa ne sakamakon abubuwan da ke lalata laka a kan gangaren nahiyar ko kuma a gefen shiryayyen nahiyar. Wasu abubuwan da suka fi haifar da su sun haɗa da:
1. Zaftarewar ƙasa a ƙarƙashin ruwa da kuma gangarawar gangara
Laka da aka tara a kan gangara na iya lalacewa (lalacewar gangara) saboda yawan lodi, girgizar ƙasa, ko canje-canje a matsin lamba a cikin ramuka. Abubuwan da ke rugujewa na iya rikidewa zuwa kwararar laka mai ruwa da hayaniya.
2. Girgizar Kasa
Girgizar ƙasa na iya kawo cikas ga kwanciyar hankali na laka kuma yana haifar da sakin kayan da aka dakatar, yana haifar da manyan kwararar ruwa mai sauri da kuma turbidity.
3. Manyan ambaliyar ruwa daga ƙasa (yawan kwararar ruwa mai yawa)
A wasu yanayi, ruwan kogi wanda yake da wadataccen laka zai iya samun yalwar ruwa fiye da ruwan teku, don haka yana "nutsewa" kuma yana gudana kamar kwararar ruwa mai yawa zuwa cikin zurfin teku.
4. Guguwa da raƙuman ruwa masu ƙarfi
A kan ƙananan shelves, guguwa na iya tayar da laka ta aika shi zuwa gefen shelves, inda yake faɗuwa ƙasan gangaren kuma yana haifar da kwararar turbidity.
5. Aikin aman wuta da kuma kwararar da ke gudana cikin teku
Ruwan aman wuta da ke shiga teku na iya gauraya da ruwa kuma su samar da kwararar laka mai yawa.
A taƙaice, kwararar ruwa tana faruwa ne lokacin da akwai wadatar laka da yanayi da ke ba da damar dattin da aka dakatar ya motsa ƙasa da isasshen kuzari.
Tsarin motsin jiki da yanayin kwarara
Ruwan turbidity yana motsawa a matsayin "girgije" na laka, sau da yawa yana da yawa a ƙasa kuma yana da siriri a sama. Saurin kwarara na iya bambanta - daga jinkiri zuwa sauri sosai - ya danganta da girman laka, yanayin gangara, da matakin turbule. A lokuta da yawa, waɗannan kwararar na iya tafiya har zuwa daruruwan kilomita daga tushen su, suna bin kwaruruka na ƙarƙashin ruwa sannan su bazu waje don samar da fanka na ƙarƙashin ruwa.
A ra'ayi, tsarin turbidity sau da yawa ana raba shi zuwa yankuna da dama:
– Yankin tushe/zagewar ƙasa: yankin gangaren inda laka ke fita da kwararar ruwa ke fara samuwa; sau da yawa inda zaizayar ƙasa mai ƙarfi ke faruwa.
– Yankin sufuri: kwararar ruwa tana da yawa a cikin tashar kuma tana iya jigilar yashi.
– Yankin da ke zubar da ƙasa: kuzari yana raguwa, hanyoyin ruwa na iya faɗaɗa ko ƙarewa, ana ajiye laka don samar da lobes da zanen yashi.
Canje-canje a cikin kuzarin kwarara kuma yana sarrafa girman hatsin da aka jigilar. Yayin da kuzarin ke raguwa, ƙwayoyin da suka yi kauri (yashi) suna farawa su kwanta, sai kuma laka da yumbu. Wannan tsari yana samar da kayan gado masu daraja wanda shine siffa ta gargajiya ta turbidites.
Tarin Turbidite da jerin Bouma
Babban samfurin kwararar turbidity shine ma'ajiyar turbidite, waɗanda ake iya gane su ta hanyar tsarin su na sedimentary da tsarin gado. Ɗaya daga cikin shahararrun samfuran don bayyana abun ciki na turbidites shine Bouma Sequence, musamman ga turbidites na "classic" na yashi-zuwa-lat. A taƙaice, wannan jerin yana bayyana canji daga babban makamashi zuwa ƙarancin kuzari a cikin wani taron adanawa guda ɗaya:
– Ta: babban yashi ko yashi mai tsari na yau da kullun (mai kauri a ƙasa, mafi ƙanƙanta zuwa sama) saboda saurin narkewar laka.
– Tb: layi mai layi ɗaya, wanda ke nuna cewa kwararar ruwan ta fara zama ruwan dare.
- Tc: ripple cross-lamination, makamashi yana raguwa.
– Td: kyakkyawan lamination akan ƙasa.
– Te: yumbu/shale mai sheƙi wanda ke narkewa a hankali bayan wani abu mai datti.
Ba dukkan turbidites ne ke nuna cikakken jerin Ta-Te ba. Yawancin ma'adanai suna nuna matakai kaɗan ne kawai, ya danganta da yanayin kwararar ruwa, wadatar laka, da kuma hanyoyin bayan an cire su.
Yanayin ƙasa mai laushi da ke da alaƙa da kwararar turbidity
Mafi yawan kwararar turbidity suna faruwa a cikin:
- Zurfin nahiyar da kuma hauhawar nahiyar
Wuri mai isasshen gangara don tuƙa kwararar ruwa mai yawa.
- Kwarurukan ƙarƙashin ruwa
Yana aiki a matsayin "tashar" wanda ke mai da hankali kan kwararar.
- Masoyan jirgin ruwa na ƙarƙashin ruwa
Babban tsarin sedimentary mai siffar fanka a cikin zurfin teku, wanda galibi ya ƙunshi ramukan tashoshi da lobes.
- Kwarin ruwa mai zurfi
Wuri ne da ake tara ƙananan ƙwayoyin cuta, musamman a ɓangaren nesa.
A cikin kwaruruka da yawa, turbidites suna tara tarin duwatsu masu kauri waɗanda ke rikodin tarihin tectonic, wadatar laka daga ƙasa, da kuma canjin matakin teku.
Me yasa kwararar turbidity take da mahimmanci?
1. Mabuɗin sake gina tarihin ƙasa
Turbidites suna yin rikodin abubuwan da suka faru a baya: zaftarewar ƙasa, girgizar ƙasa, ko manyan ambaliyar ruwa. Ta hanyar nazarin yanayin shimfidar su da rarrabawar su, masana ilimin ƙasa za su iya fassara yanayin yanayin kwarin da canje-canje a cikin yanayin da ke ƙarƙashin ƙasa a tsawon lokaci.
2. Ya dace da binciken mai da iskar gas
Yawancin ma'ajiyar hydrocarbon suna cikin duwatsu masu turbidite, musamman a cikin tsarin fanka na ƙarƙashin ruwa. Duwatsun turbidite na iya samun kyakkyawan porosity da permeability, kodayake bambancin su na ciki yana buƙatar yin ƙira mai kyau.
3. Yana taimakawa wajen fahimtar haɗarin ilimin ƙasa a ƙarƙashin ruwa
Guduwar turbidity na iya lalata kayayyakin more rayuwa kamar kebul na sadarwa na ƙarƙashin ruwa da bututun mai. Fahimtar hanyoyin da yiwuwar faruwar turbidity yana da amfani don rage haɗari.
4. Muhimmanci ga nazarin ilimin halittar paleoseism
A wasu yankuna, ana iya haɗa layukan turbidite da manyan girgizar ƙasa da suka gabata. Wannan ya sa turbidites ya zama "tarihin" halitta don nazarin yawan girgizar ƙasa a yankunan da ke ƙarƙashin ƙasa.
Yadda ake gane turbidites a cikin filin ko kuma tsakiyar haƙa rami
Masanin nazarin ƙasa yawanci yana gano turbidites ta hanyar haɗa waɗannan halaye:
- Tsarin da aka tsara na yau da kullun (girman hatsi yana ƙaruwa sama).
– Tsarin laminate na Bouma (ɓangare ko cikakke).
– Hulɗar tushen tana da kauri kuma wani lokacin tana ɗauke da alamun tafin ƙafa (misali simintin sarewa) waɗanda ke taimakawa wajen tantance alkiblar paleocurrents.
- Maimaitawar fakitin da ke nuna abubuwan da suka faru a baya (gadajen taron).
- Canjin gefe daga ma'ajiyar tashoshi (mai kauri da kauri) zuwa ma'ajiyar lobe/overbank (mai siriri da ƙanƙanta).
Sau da yawa ana amfani da nazarin girman hatsi, nazarin petrography, da bayanan ƙasa (misali, girgizar ƙasa) don zana taswirar yanayin jikin yashi mai turbidite a kan sikelin kwano.
Penutup
Ruwan turbidity kwararar ruwa ce mai cike da laka wadda ke tafiya a ƙarƙashin ruwa saboda bambancin yawa da nauyi. Wannan tsari yana samar da ma'ajiyar turbidite, waɗanda ke da layuka daban-daban, waɗanda galibi ake siffanta su da Jerin Bouma. A fannin nazarin ƙasa, ruwan turbidity yana da mahimmanci saboda suna sarrafa jigilar laka zuwa zurfin teku, suna gina tsarin fanka na ƙarƙashin ruwa, da kuma adana bayanai game da abubuwan da suka faru a baya a fannin ƙasa. Bugu da ƙari, fahimtar turbidity kuma yana da tasiri mai amfani ga binciken albarkatu da rage haɗari ga kayayyakin more rayuwa na ƙarƙashin ruwa. Ta hanyar nazarin turbidity, a zahiri muna karanta "bayanin abubuwan da suka faru" waɗanda suka faru a ƙasan teku kuma suka tsara yanayin laka da muke fuskanta a yau.
