Yankin Cretaceous-Paleogene

Yankin Cretaceous-Paleogene (K-Pg), wanda aka fi sani da iyaka Cretaceus-Tertiary (K-T), sa hannu ne na ilimin ƙasa, yawanci ƙaramin rukuni na dutse wanda ke dauke da iridium fiye da sauran rukuni. Yankin K-Pg iyaka nuna ƙarshen zamanin Cretaceous, Lokacin ƙarshe na zamanin Mesozoic, kuma yana nuna farkon zamanin Paleogene, lokacin farko na zamanin Cenozoic. Yawanci ana kimanta shekarunta a shekaru miliyan 66,  tare da kwanan wata na radiometric wanda ke samar da ainihin shekaru na 66.043 ± 0.043 Ma. 

Yankin K-Pg yana da alaƙa da taron lalacewar Cretaceous-Paleogene, lalacewar jama'a wanda ya lalata yawancin nau'in Mesozoic na duniya, gami da dukkan dinosaur ban da wasu tsuntsaye.

Akwai shaidu masu karfi cewa halaka ta dace da babban tasirin meteorite a cikin rami na Chicxulub kuma ka'idar kimiyya da aka yarda da ita ita ce wannan tasirin ya haifar da halaka.

Kalmar "Cretaceous" ta samo asali ne daga Latin "creta" (chalk). An taƙaita shi K (kamar yadda yake a cikin "K-Pg iyaka") don fassarar Jamusanci "Kreide" (chalk). 

 Dalilan da aka gabatar 

 Rashin ruwa na Chicxulub 

A cikin 1980, ƙungiyar masu bincike karkashin jagorancin masanin kimiyyar Nobel Walter Alvarez">Luis Alvarez, ɗansa, masanin ilimin ƙasa Walter Alvarez, da masana sunadarai Frank Asaro da Helen Vaughn Michel sun gano cewa yadudduka da aka samo a duk duniya a iyakar Cretaceous-Paleogene suna dauke da maida hankali ga iridium sau daruruwan fiye da yadda aka saba. Sun ba da shawarar cewa wannan Layer shaida ce ta wani tasiri wanda ya haifar da rushewar yanayi a duniya kuma ya haifar da lalacewar Cretaceous-Paleogene, lalacewar taro wanda kashi 75% na nau'in shuke-shuke da dabbobi a Duniya ba zato ba tsammani suka ƙare, gami da duk dinosaur da ba tsuntsaye ba.

Lokacin da aka fara gabatar da shi, matsala daya tare da "Alvarez hypothesis" (kamar yadda aka sani) shi ne cewa babu wani rami da aka rubuta wanda ya dace da taron. Wannan ba mummunan rauni ba ne ga ka'idar; yayin da rami wanda ya haifar da tasirin zai kasance ya fi    a diamita, hanyoyin ilimin ƙasa na Duniya sun ɓoye ko lalata craters a tsawon lokaci.

Crater na Chicxulub wani rami ne mai tasiri wanda aka binne a ƙarƙashin Yucatán Peninsula a Mexico .  Cibiyarta tana kusa da garin Chicxulub, bayan haka aka sanya sunan rami. An kafa shi ne ta hanyar babban Asteroid ko Comet kimanin kilomita 10-15 (6.2-9.3  a diamita,  mai tasiri na Chicxulub, ya buge Duniya. Ranar tasirin ya dace daidai da iyakar Cretaceous-Paleogene (K-Pg iyaka), dan kadan fiye da shekaru miliyan 66 da suka gabata.

 Rashin Hanci 
Kafin shekara ta 2000, muhawara cewa ambaliyar ruwa ta Deccan Traps ta haifar da halaka yawanci ana danganta su da ra'ayin cewa halaka ta kasance sannu a hankali, kamar yadda ake zaton ambaliyar basalt ta fara ne a kusa da 68 Ma kuma ta dauki sama da shekaru miliyan 2. Koyaya, akwai shaidar cewa kashi biyu cikin uku na Deccan Traps an halicce su ne a cikin shekaru miliyan 1 game da 65.5 Ma, don haka waɗannan fashewar zasu haifar da halaka da sauri, mai yiwuwa lokaci na dubban shekaru, amma har yanzu lokaci ne mai tsawo fiye da abin da za a sa ran daga wani abu mai tasiri

Deccan Traps na iya haifar da halaka ta hanyar hanyoyin da yawa, gami da sakin ƙura da sulfuric aerosols cikin iska wanda zai iya toshe hasken rana kuma ta haka ne ya rage photosynthesis a cikin tsire-tsire. Bugu da kari, Deccan Trap volcanism na iya haifar da hayakin carbon dioxide wanda zai kara tasirin greenhouse lokacin da ƙura da aerosols suka share daga yanayi.Duncan, RA; Pyle, DG (1988). 

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