The Mongol-Okhotsk Ocean also known as the Khangai-Khantey Ocean was an ancient ocean, present during the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

. Oceanic rocks from the ancient ocean floor are preserved in the Mongol-Okhotsk suture zone extending through

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

to the

Sea of Okhotsk The Sea of Okhotsk; Historically also known as , or as ; ) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands on the southeast, Japan's island of Hokkaido on the sou ...

Sequence of events

With the formation of the supercontinent

Pangea Pangaea or Pangea ( ) was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia (continent), Siberia during the Carboniferous period ...

in the mid- to late-

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

, the vast

Panthalassa Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek "all" and "sea"), was the vast superocean that encompassed planet Earth and surrounded the supercontinent Pangaea, the latest in a series of supercontinent ...

ocean dominated 70 percent of the Earth's surface. The Tethys, Mongol-Okhotsk and various small domains of early Pacific Ocean crust constituted other small oceans. Paleomagnetic data collected between 1987 and 2010 suggest that the Mongol-Okhotsk oceanic crust subducted under the terranes of Mongolia in the

Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...

Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...

. During the early Mesozoic, the Solonker Ocean, also known as the Intra-Asian Ocean closed bringing together two large continental blocks: Amuria and the North China Block. Amuria then collided with the Siberian Craton, preserving the Mongol-Okhotsk suture zone. Geologists debate why the suture zone ends abruptly near Kazakhstan and have used seismic tomography to develop different interpretations. Most exposed rocks in the suture zone are thrusted accretionary wedges, often with

ophiolites An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle (Earth), upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is ...

. Uranium-lead dating of

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

dolerite Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grain ...

gabbro Gabbro ( ) is a phaneritic (coarse-grained and magnesium- and iron-rich), mafic intrusive igneous rock formed from the slow cooling magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ch ...

as well as

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the third and shortest period of t ...

radiolarite gives ages constraints on the formation of the oceanic crust. Dated rocks in the Adaatsag ophiolite in the east are among the oldest at 325 million years old.

Weblinks

* Mingshuai Zhu, Daniel Pastor–Galán, Matthijs A. Smit, Dorjgochoo Sanchir, Fuqin Zhang, Chenghao Liu, Ye Luo, Laicheng Miao: ''The Beginning of a Wilson Cycle in an Accretionary Orogen: The Mongol–Okhotsk Ocean Opened Assisted by a Devonian Mantle Plume.'' In: ''Geophysical Research Letters'', Volume 51, Issue 10, 28. May 2024, e2024GL109028; doi:10.1029/2024GL109028. Epub 16 May 2024. ** Stephanie Pappas
Boiling rocks from Earth's crust tore an ocean into Mongolia 410 million years ago
LiveScience, June 26, 2024

References

{{reflist Historical oceans Geology of Russia Geology of Mongolia

Sequence of events

See also

Weblinks

References