Pre-Nectarian

Pre-Nectarian

The Pre-Nectarian Period of the lunar geologic timescale runs from 4533 million years ago (the time of the initial formation of the Moon) to 3920 million years ago, when the Nectaris Basin was formed by a large impact. It is followed by the Nectarian period. Pre-Nectarian rocks are rare in the lunar sample suite; they are mostly composed of lunar highlands material which have been heavily churned, brecciated, and thermally affected by subsequent impacts, particularly during the Late Heavy Bombardment that marks the approximate beginning of the Nectarian Period. The primary Pre-Nectarian lunar highland material is dominated by the rock type anorthosite, which suggests that the early stage of lunar crustal formation occurred via mineral crystallization of a global magma ocean.

This geologic period has been informally subdivided into the Cryptic Era (4.533 - 4.172 Ga ago) and Basin Groups 1-9 (4.172 - 3.92 Ga ago),cite book | title = [http://ser.sese.asu.edu/GHM/ Geologic History of the Moon] | last = Don Wilhelms | publisher = U.S. Geological Survey Professional Paper 1348 | year = 1987] but these divisions are not used on any geologic maps.

Relationship to Earth's geologic time scale

Since little or no geological evidence on Earth exists from the time spanned by the Pre-Nectarian period of the Moon, the Pre-Nectarian has been used as a guide by at least one notable scientific work [cite book | title = A Geologic time scale 1989 | publisher = Cambridge University Press | year = 1990 | last = W. Harland, R. Armstrong, A. Cox, L. Craig, A. Smith, D. Smith] to subdivide the unofficial terrestrial Hadean eon. In particular, it is sometimes found that the Hadean eon is subdivided into the Cryptic era, Basin Groups 1-9, Nectarian and Lower Imbrian, though the first two of these lunar divisions are informal and collectively make up the Pre-Nectarian.

References

External links

*http://www.palaeos.org/Hadean


Wikimedia Foundation. 2010.

Игры ⚽ Нужен реферат?

Look at other dictionaries:

  • Nectarian — Divisions of  Lunar geologic time : Pre Nectarian Nectarian Early Imbrian Late Imbrian Eratosthenian Copernican The Nectarian Period of the lunar geologic timescale runs from 3920 million years ago to 3850 million years ago. It is the… …   Wikipedia

  • Lunar geologic timescale — The lunar geologic timescale (or selenologic timescale) divides the history of Earth s moon into five generally recognized geologic periods: the Copernican, Eratosthenian, Imbrian (upper and lower), Nectarian, and Pre Nectarian. The boundaries of …   Wikipedia

  • Basin Groups — refers to 9 informal subdivisions of the lunar Pre Nectarian geologic period. DefinitionThe motivation for creating the Basin Groups subdivisions was to place 30 pre Nectarian impact basins into 9 relative age groups. The relative age of the… …   Wikipedia

  • Borealis quadrangle — The Borealis quadrangle is a quadrangle on Mercury surrounding the north pole down to 65° latitude (see also: geography of Mars).It contains the Goethe Basin, whose diameter of at least convert|400|km|abbr=on makes it the sixth largest impact… …   Wikipedia

  • Planetary science — Planetary science, also known as planetology and closely related to planetary astronomy, is the science of planets, or planetary systems, and the solar system. Incorporating an interdisciplinary approach, planetary science draws from diverse… …   Wikipedia

  • Graphical timeline of our universe — This more than twenty billion years timeline of our universe shows the best scientific estimates of the occurrence of events since its beginning, up until anticipated events in the near future. Zero of the scale is the present day. A large step… …   Wikipedia

  • Geologic time scale — This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga.[1] Other… …   Wikipedia

  • Mare Fecunditatis — Coordinates …   Wikipedia

  • Mare Smythii — Coordinates …   Wikipedia

  • Copernican period — Divisions of  Lunar geologic time : Pre Nectarian Nectarian Early Imbrian Late Imbrian Eratosthenian Copernican The Copernican Period in the lunar geologic timescale runs from approximately 1.1 billion years ago to the present day. The… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”