Abubuwan da suka faru na Cretaceous-Paleogene

Cretaceous-Paleogene (K-Pg) bacewar taron, wanda aka fi sani da Cretaceus-Tertiary (K-T) bacewar, shine bacewar kashi uku cikin hudu na shuka da nau'in dabbobi a Duniya  kimanin shekaru miliyan 66 da suka gabata.Wannan taron ya haifar da halakawar dukkan dinosaur da ba tsuntsaye ba. Yawancin sauran tetrapods da ke da nau'o'in fiye da    suma sun ƙare, ban da wasu nau'in ectothermic kamar turtles na teku da crocodilians. Ya nuna ƙarshen zamanin Cretaceous, kuma tare da shi zamanin Mesozoic, yayin da yake sanar da farkon zamanin geological na yanzu, Zamanin Cenozoic. A cikin rikodin ilimin ƙasa, taron K-Pg yana da alama ta wani nau'i mai laushi da ake kira iyakar K-PG ko iyakar K'T, wanda za'a iya samunsa a duk faɗin duniya a cikin duwatsu na ruwa da na ƙasa. Yumbu na iyaka yana nuna matakan iridium na ƙarfe,   wanda ya fi yawa a cikin Asteroids fiye da a cikin ɓawon burodi na Duniya. 

Kamar yadda aka gabatar da shi a shekarar 1980  ta ƙungiyar masana kimiyya karkashin jagorancin Luis Alvarez da ɗansa Walter, yanzu ana tunanin cewa lalacewar K-Pg ta haifar da tasirin Babban asteroid 10 zuwa 15   mai faɗi,   shekaru miliyan 66 da suka gabata wanda ya haifar da tasirin tasirin Chicxulub, wanda ya lalata yanayin duniya, galibi ta hanyar Tasirin hunturu wanda ya dakatar da photosynthesis a cikin shuke-shuke da plankton. Tunanin tasirin, wanda aka fi sani da Ra'ayin Alvarez, an ƙarfafa shi ta hanyar gano 180   Chicxulub crater a cikin Gulf of Mexico's Yucatán Peninsula a farkon shekarun 1990,  wanda ya ba da tabbacin cewa yumbu na iyakar K-Pg yana wakiltar tarkace daga Tasirin asteroid.  Gaskiyar cewa lalacewar ta faru a lokaci guda tana ba da tabbaci mai ƙarfi cewa asteroid ne ya haifar da su. Wani aikin hakowa na 2016 a cikin zobe na Chicxulub ya tabbatar da cewa zobe na saman ya ƙunshi dutse da aka fitar a cikin minti kaɗan daga zurfin ƙasa, amma yana ƙunshe da kusan wani gypsum, dutsen da ke dauke da sulfate na yau da kullun a yankin: gypsum zai narke kuma ya warwatse a matsayin aerosol a cikin yanayi, yana haifar da tasirin lokaci mai tsawo akan yanayi da jerin abinci. A watan Oktoba na 2019, masu bincike sun tabbatar da cewa taron ya hanzarta ya yi wa teku ƙanƙara kuma ya haifar da sakamako mai tsawo a kan yanayi, yana ba da cikakken bayani game da hanyoyin halakawar jama'a.

Sauran abubuwan da suka haifar ko abubuwan da suka ba da gudummawa ga halaka na iya zama Deccan Traps da sauran fashewar dutsen wuta,   Canjin yanayi, da canjin matakin teku. Koyaya, a cikin Janairu 2020, masana kimiyya sun ba da rahoton cewa samfurin yanayi na taron halaka ya fi son tasirin asteroid ba dutsen wuta ba.

Yawancin nau'in nau'in nau'in ƙasa sun lalace a cikin halakar K-Pg, wanda aka fi sani da shi shine dinosaur wadanda ba na ruwa ba, tare da dabbobi masu shayarwa, tsuntsaye,  kadangaru,  kwari,   tsire-tsire, da duk pterosaurs .  A cikin tekunan duniya, K-Pg taro kashe kashe plesiosaurs da mosasaurs da lalata teleost kifi,  sharks, mollusks (musamman ammonites da rudists, wanda ya zama bace), da kuma yawancin nau'in plankton. An kiyasta cewa kashi 75% ko fiye na dukkan nau'in dabbobi da na ruwa a Duniya sun bace.  Duk da haka, ɓarna kuma ya ba da damar juyin halitta : a cikin farkawa, ƙungiyoyi da yawa sun sami raɗaɗi mai dacewa - kwatsam da rarrabuwar kawuna zuwa sabbin nau'ikan nau'ikan nau'ikan nau'ikan halittu a cikin rugujewa da ɓarna abubuwan muhalli. Dabbobi masu shayarwa musamman sun bambanta a cikin waɗannan Zamanin Paleogene,  suna haɓaka sabbin sifofi kamar dawakai, whales, jemagu, da primates . Rukunin dinosaur da suka tsira sun kasance avians, wasu ƴan nau'in tsuntsayen ƙasa da na ruwa, waɗanda suka mamaye duk nau'ikan tsuntsayen zamani.  Daga cikin sauran kungiyoyi, kifin teleost  da watakila kadangaru  suma sun haskaka cikin nau'ikan su na zamani.

 Manazarta