Miocene_Geology_Mini_Project

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The Miocene

Epoch

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The Miocene Epoch 23 MYA to 5.33 MYA

A period of warming whose cause appears to be from multiple sources such as basalt (an igneous rock) offgassing CO2, changing Milankovitch cycles, and other currently unknown sources2

The Early Miocene Cool Interval (EMCI) was a period of cooling was caused by a significant expansion of the Antartic ice sheet (which existed during this epoch)1

Middle Miocene Warm Interval (MMWI)18MYA - 14MYA

Early Miocene Cool Interval (EMCI)23MYA - 18MYA

What was the Miocene World was Like:Climate

The Miocene was overall a time of cooling for the planet, but it was marked by several interesting dynamic climatic events.

Middle Miocene Climate Transition (MMCT)14MYA - 11MYA

Global temperatures fell compared to the MMWI. It is believed to be caused by carbon dioxide withdrawal (CO2) from the atmosphere by high primary productivity in the Eastern Equitorial Pacific Ocean

Global temperature likely continued to drop as a result of decreased carbon dioxide (CO2) levels and an increased orbital distance from the Sun.

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What was the Miocene World was Like:Climate

Late Miocene Cool Interval (LMCI)11MYA - 5MYA

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Cetaceans, which are ocean mammals who have a fully aquatic lifestyle and carnivorous diet, had the greatest amount of biodiversity during the Miocene. You could find many within the oceans of the Miocene.

Grazers dominated the ubiquitous grasslands of the Miocene. Fossils of grazers like horses, camels, and rhinoceroses, have been found in what is now Texas, Kansas, and Nebraska2.

Grasslands expanded due to the cooler climate of the Miocene mainly in the low to middle latitude parts of the word like North America, Eurasia, Africa, etc.. These grasses were of the C4 type. Fossils from the genuses Berriochloa, Nassella, and Paleoeriocoma1 are commonly found in Miocene strata.

Cetaceans

Primates

Grazers

Grasses

What was the Miocene World Like: Flora and Fauna of the Miocene

cross-section of the crater Krakul Lake sits in

Major Event: Tajikstan Impact Event

Krakul Lake in Tajikstan, a country in Central Asia, is the result of a large asteroid impact during the Miocene. The exact date of the impact is unknown, some date it as being as young as 5 MYA, while others date it at 25 MYA2, but it likely occured during the Miocene. The impact created Krakul Lake 12,990 ft above sea level. An excerpt taken from The Karakul Depression in Pamirs - The First Impact Structurein Central Asia about the lake is below:The Karakul crater is presented by the circular depression with the flat floor and uplifted rim. The rim-rim diameter is about 52 km. The bottom of the depression 30 in diameter is occupied by the Karakul Lake and unconsolidated lacustrine deposites. The central uplift forms an island and peninsula in the, lake in the middle part of the depression. The height of the uplift is to 250-300 m above the lake level. The elevation of the rim is about 10OO m above the floor of the depression and about 120-2OO m above the surrounding area.

Parts of Japan during the miocene was either underwater, or exposed as dry land. The Korean Peninsula is to the west for comparison and it still a landmass albeit with a much bigger shorelines

4. Snakes came into prominence during the Miocene.

Snakes before the Miocene were existing, but once the epoch began they started to thrive. Vipers, and other modern genuses of snakes arose during this epoch1. This is when snakes started to become biodiverse

3. Africa and the Arabian Peninsula Collided during the Miocene

This occured during the Early Miocene but the newly conneted landmsses exchanged a wealth of plants, animals, fungi, etc.

2. Japan was Unrecgnoziable!

1. The Miocene can be used as an analogue for what conditions Humans will experience due to climate change

During the Middle Miocene Warm Interval (MMWI), the earth had similar concentrations of carbon dioxide as today, making the Miocene an important geologic epoch of study. Scientists can predict what we will experience by looking at the Miocene.

4 Fun Facts About the Miocene

Primates: The Most Important Organism of All

Primates are of such importance that they deserve their own window of information. Primates during the Miocene flourished and the first bipedal apes, organisms who also belong to primates, bipedalism being walking upright on two feet, came into existance as a result of the decline of forests, and the rise of grasslands during the Miocene. The first bipedal ape, Sahelanthropus, was found in this epoch about 7 MYA3. Primates were present throughout Africa, Asia, and Europe.

Skull of the Sehalnthropus Genus, found in Chad. image source: By Didier Descouens - Own work, CC BY-SA 4.0,.

Here is how the World looks Today for comparison !

Here is how the World looks Today for comparison !

1. Thomasson, J. R. (1985). Miocene Fossil Grasses: Possible Adaptation in Reproductive Bracts (Lemma and Palea). Annals of the Missouri Botanical Garden, 72(4), 843–851. https://doi.org/10.2307/2399226 2. 2. Thomasson, J. R. (1985). Miocene Fossil Grasses: Possible Adaptation in Reproductive Bracts (Lemma and Palea). Annals of the Missouri Botanical Garden, 72(4), 843–851. https://doi.org/10.2307/23992263.3. Brunet, M.; Guy, F.; Pilbeam, D.; et al. (2002). "A new hominid from the Upper Miocene of Chad, Central Africa" (PDF). Nature. 418 (6894): 145–151.

Sources

1: Greenop, R., Sosdian, S. M., Henehan, M. J., Wilson, P. A., Lear, C. H., & Foster, G. L. (2019). Orbital forcing, ice volume, and CO2 across the Oligocene-Miocene transition. Paleoceanography and Paleoclimatology, 34, 316–328. https://doi.org/10.1029/2018PA0034202.Scotese, Christopher R.; Song, Haijun; Mills, Benjamin J.W.; van der Meer, Douwe G. (April 2021). "Phanerozoic paleotemperatures: The earth's changing climate during the last 540 million years" (PDF). Earth-Science Reviews. 215: 103503

Sources

Geological Time Scale Source: Image by Jonathan R. Hendricks for the Earth@Home project.Miocene Map Source: http://www.stromboidea.de/bilder/Miocene_20_Ma.jpg, copyright Ron Blakey.Modern World Map Source: https://www.mapsinternational.com/medium-satellite-map-of-the-world-laminated.html

Sources Used to Create this Page:

Ann Holbourn, Wolfgang Kuhnt, Mitch Lyle, Leah Schneider, Oscar Romero, Nils Andersen; Middle Miocene climate cooling linked to intensification of eastern equatorial Pacific upwelling. Geology 2014;; 42 (1): 19–22. doi: https://doi.org/10.1130/G34890.1Flower, Benjamin P.; Kennett, James P. (April 1994). "The middle Miocene climatic transition: East Antarctic ice sheet development, deep ocean circulation and global carbon cycling". Palaeogeography, Palaeoclimatology, Palaeoecology. 108 (3–4): 537–555. Bibcode:1994PPP...108..537F. doi:10.1016/0031-0182(94)90251-8

Sources

1. Holman, J. Alan (2000). Fossil Snakes of North America (First ed.). Bloomington, IN: Indiana University Press. pp. 284–323. ISBN 0-253-33721-6.2. Map of Miocene-epoch Japan source: Kameda Y. & Kato M. (2011). "Terrestrial invasion of pomatiopsid gastropods in the heavy-snow region of the Japanese Archipelago". BMC Evolutionary Biology 11: 118. doi:10.1186/1471-2148-11-118. Figure 5B. 3. Map of Miocene Earth 20 MYA source: Miocene Map Source: http://www.stromboidea.de/bilder/Miocene_20_Ma.jpg, copyright Ron Blakey.

Sources