Cretaceous–Paleogene boundary Cretaceous–Paleogene boundary The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K-T) boundary, is a geological signature, usually a thin band of rock. "K", the first letter of the German word "Kreide" (chalk), is the traditional abbreviation for the Cretaceous Period and "Pg" is the abbreviation for the Paleogene Period. The K–Pg boundary marks the end of the Cretaceous Period, the last period of the Mesozoic Era, and marks the beginning of the Paleogene Period, the first period of the Cenozoic Era. Its age is usually estimated at around 66 Ma (million years ago), with radiometric dating yielding a more
Geography of Switzerland term covers entire geological movements contributing to the of the Alps’ formation. A crystalline basement formed at the beginning of the Paleozoic era, between 540 and 360 millions years ago. Later, between 205 and 96 million years ago, the alpine ocean or Tethys Ocean formed between Eurasia and Africa. The ocean reached its maximum width at the end of Jurassic period, 135 million years ago. The collision between the Eurasian and African plates made it progressively disappear. This plate collision (still in progress) began 100 million years ago. The Alps resulted from this geological movement, the two plates creating folding