Eocene Geology

Eocene geology, spanning from 56 to 33.9 million years ago, documents a critical transition in Earth's structure and climate driven by significant plate tectonic activity. This epoch was dominated by the collision of the Indian subcontinent with Asia, a monumental event that initiated the uplift of the Himalayan mountains and the Tibetan Plateau. Simultaneously, the separation of Australia from Antarctica and the widening of the North Atlantic opened key oceanic gateways, establishing new circulation patterns like the Antarctic Circumpolar Current. This fundamental shift in oceanography triggered a long-term global cooling trend, moving the planet from an early "hothouse" state toward future ice ages, a process recorded in widespread marine and terrestrial sedimentary deposits like the fossil-rich Green River Formation of North America.

  1. Introduction to the Eocene Epoch
    1. Definition and Overview
      1. Meaning and Etymology
        1. Key Characteristics
          1. Importance in Earth History
          2. Chronological Placement
            1. Position in the Geologic Time Scale
              1. Cenozoic Era Context
                1. Paleogene Period Framework
                  1. Relationship to Adjacent Epochs
                  2. Absolute Time Boundaries
                    1. Start Date (56.0 Ma)
                      1. End Date (33.9 Ma)
                        1. Duration and Significance
                        2. Dating Methods
                          1. Radiometric Dating Techniques
                            1. Biostratigraphic Correlation
                              1. Magnetostratigraphic Methods
                              2. Boundary Events
                                1. Paleocene-Eocene Boundary
                                  1. Eocene-Oligocene Boundary
                                    1. Global Stratotype Sections
                                  2. Subdivisions of the Eocene
                                    1. Ypresian (Early Eocene)
                                      1. Time Range (56.0-47.8 Ma)
                                        1. Defining Stratotype
                                          1. Characteristic Features
                                            1. Major Events
                                            2. Lutetian (Middle Eocene)
                                              1. Time Range (47.8-41.2 Ma)
                                                1. Stratigraphic Definition
                                                  1. Regional Variations
                                                    1. Notable Fossil Assemblages
                                                    2. Bartonian (Middle Eocene)
                                                      1. Time Range (41.2-37.71 Ma)
                                                        1. Type Section
                                                          1. Environmental Conditions
                                                            1. Biotic Changes
                                                            2. Priabonian (Late Eocene)
                                                              1. Time Range (37.71-33.9 Ma)
                                                                1. Boundary Criteria
                                                                  1. Climatic Transitions
                                                                    1. End-Eocene Events