paleobiology, paleoclimate

Highlights of the Phanerozoic: Part 3 – Cenozoic [65 Ma – on]

Here’s a few highlights from the history of the Earth and life during the Cenozoic Era, the third of the Phanerozoic, which is the fourth Eon in Earth’s history. These events are mainly focused on North America, and the dates of Periods and Epochs are partially rounded.

CENOZOIC (CZ) [65 Ma – on]

PALEOGENE (PE) [65 – 23 Ma]

PALEOCENE (PE) [65 – 56 Ma]

  • Radiation of placental mammals
  • Paleocene-Eocene Thermal Maximum (PETM)
    • Extinctions and reorganizations in land ecosystems (deep marine)
    • Release of biogenic C, huge drop in CaCO3

EOCENE (EO) [56 – 34 Ma]

  • Greenhouse world; no ice anywhere, higher sea level
  • Late: steady cooling – building of Himalayas and closure of Tethys
    • CO2 sequestration via silicate weathering
  • Abrupt cooling of Late – Antarctica split from Gondwanaland [35 Ma]
    • Circum-Antarctic current
  • Dominance of mega-mammals
  • Laramide basin fills-in with alluvial fans
  • Beginning of ignimbrite flare-ups [40-20 Ma]
    • Explosive rhyolitic volcanism from subduction of Farallon plate
  • Chesapeake Bay impact [35 Ma] – no significant effects on biosphere

OLIGOCENE (OG) [ 34 – 23 Ma]

  • Start of rifting in East Africa [30 Ma]
  • Beginning of Basin and Range extension [25 Ma – present]
    • Change in California plate boundary from convergence to strike-slip
    • Metamorphic core complexes; tectonic contact between shallow and deep rock
  • Uplift of Colorado Plateau [25 Ma – present]
    • Respond to regional stretching and uplift; downcutting

NEOGENE (N) [23 – 2.6 Ma]

MIOCENE (MI) [23 – 5.3 Ma]

  • Cascade arc volcanism [20 Ma – present]
    • Subduction of Juan de Fuca plate
  • Columbia River basalts [16-14 Ma] – crustal fissures, hotspot
  • Start of Snake River volcanism [14-2 Ma]
    • Hotspot, traveling plume (same from Columbia River)
  • Late MI to early PO – Messinian salinity crisis [6-5 Ma]
    • Mediterranean cut off from Atlantic, dried up many times over (evaporate deposits)

PLIOCENE (PO) [5.3 – 2.6 Ma]

  • Ardipithecus ramidus (“Ardi”) [4.4 Ma]
    • Last common ancestor with modern apes
  • Australopithecus afarensis (“Lucy”) [3.3 Ma]
  • Formation of Panama isthmus [3 Ma] – Great American Interchange
    • Isolates Atlantic and Pacific, thermohaline circulation, Atlantic becomes more saline, sets stage for Ice Age
  • Starts to become really sensitive to Milankovitch cycles [3 Ma]

QUARTERNARY (Q) [2.6 Ma – on]

PLEISTOCENE (PS) [2.6 Ma – 10 ka]

  • The Great Ice Age
  • Yellowstone hotspot [2 Ma – present] – trail from Snake River
  • Earliest members of Homo sapiens in Africa and Europe [500 – 300 ka]
  • “Mitochondrial Eve” out-of-Africa [100 ka]
  • Humans cross Beringia [25 ka]
  • 4 U.S. glaciations – Nebraskan, Kansan, Illinoisan, and Wisconsinan
  • Lake Missoula, Scablands floods [15-13 ka]
  • Lake Agassiz catastrophically drain through Hudson Bay [11 ka]
    • Shut down thermohaline conveyor, temporarily return Earth to Ice Age conditions

HOLOCENE (H) [10 ka- on]

  • Eruption of Mount Mazama [8 ka]
  • Unusual climate stability, allows for humans to thrive

ANTHROPOCENE ? [100 yr bp?]

  • Humans radically altering major Earth systems, outstrip rates of many geological processes

Make sure you check out Part 1 – Paleozoic and Part 2 – Mesozoic!

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