A History of Agriculture in India v1.c11.4

v1.c11.4

The Cenozoic Era is divided into two periods—the Tertiary and the Quaternary. The Tertiary is subdivided into five epochs. The name of each epoch ends with the suffix cene (Greek, recent), and refers to the progress of life. Originally it was done on the basis of the percentage of living species of molluscs found in the rocks, but later certain marked palaeontologic characters as well as physical events were included. The Tertiary Period has been studied in greater detail than any other period, partly because its flora and fauna bear close similarities to the living forms, but mainly because of economic reasons, viz. search for petroleum, of which more than 50 per cent of the world production comes from the Tertiary rocks.