PP21B-2241
Detailed view into the dynamics of the Late Miocene glaciation episode that accompanied terrestrial evolution
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Alexandrina Tzanova, Brown University, Earth, Environmental and Planetary Science, Providence, RI, United States; Central Connecticut State University, Geology, New Britain, CT, United States, Timothy Herbert, Brown Univ, Providence, RI, United States, Kira T Lawrence, Lafayette College, Easton, PA, United States, Laura Peterson, Luther College, Decorah, IA, United States and Christopher Sean Kelly, Brown University, Providence, RI, United States
Abstract:
We focus on the period of ~ 9 – 5 Ma when an episode of notably cool temperatures corresponds to evidence of high latitude Northern Hemisphere glaciation and mid-latitude terrestrial evolution. Alkenone-based sea surface temperatures (SST) from six globally distributed sites: ODP Sites 907 and 982 in the North Atlantic, ODP Site 1088 in the South Atlantic and ODP Sites 883, 884 and 887 in the North Pacific, and the Monte dei Corvi marine section in the Mediterranean unequivocally establish a dramatic, Late Miocene cold episode that persisted over approximately 2.5 Myr. In this work we establish the timing and synchronization of temperature decrease as well as rebound at orbital timescales. All sites were notably warmer than their modern annual average at ~9 Ma and exhibit sustained cooling beginning at ~8 Ma. SSTs rebound close to ~5.9 Ma at most locations suggesting that the cooling trend that began in the Late Miocene slowed down or even reversed in some locations in the Pliocene. The newly reconstructed SSTs highlight the role of cooling and an increase in equator to pole temperature gradients in terrestrial evolution at this pivotal time.
