The Miocene World: A Brief Summary

This paper presents a brief synopsis of the Miocene Epoch, an important transitory chapter in the history of the Earth. It was during the Miocene that the major continents and oceans attained a “modern” configuration in terms of paleogeography and tectonics, oceanic ventilation and circulation, ocean chemistry, and faunal and floral assemblages. It also was during the Miocene that global climate fully transitioned into its current icehouse state, including marked growth of the Antarctic ice sheet and initiation of the Arctic ice cap. Long-term global cooling was controlled by a number of factors including tectonics, the large-scale changes in the distribution of flora, particularly the expansion of grasslands, and by fluctuating orbital parameters of the Earth. This global cooling trend was briefly interrupted by a short period of warming in the middle Miocene. Miocene sea-level changes consisted of a number of glacio-eustatic third-order (1–5 million year [m.y.] duration) cycles superposed upon three longer-term, second-order (5–20 m.y. duration) supercycles. Development of large-scale tropical carbonate systems in the Miocene was relegated to three main geographic regions: the circum-Caribbean, Mediterranean, and Indo-Pacific. In addition, a pronounced cool-water platform system developed along the southern margin of Australia. Miocene reefal buildups were dominated by tropical to subtropical framework assemblages consisting primarily of large scleractinian corals, encrusting red algae, and rhodoliths (free-living coralline red algae) that grew on platform margins and interiors or on isolated atolls. Miocene carbonates were deposited in a variety of oceanic and structural settings and constitute important petroleum reservoirs, particularly in Southeast Asia. Deep-water terrigenous clastic sediments of Miocene age are also important petroleum reservoirs in some regions. In addition, the Miocene interval contains numerous prolific petroleum source rocks, most composed of Type III (gas-prone) kerogen.