Earth:Ectasian

Short description: Second period of the Mesoproterozoic Era

Ectasian
1400 – 1200 Ma Had'n Archean Proterozoic Pha.
Map of Earth in the late Ectasian, c. 1260 Ma
Chronology
Template:Ectasian graphical timeline
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Period
Stratigraphic unit	System
Time span formality	Formal
Lower boundary definition	Defined chronometrically
Upper boundary definition	Defined chronometrically

The Ectasian Period (from Ancient Greek:, meaning "extension") is the second geologic period in the Mesoproterozoic Era and lasted from 1400 Mya ago to 1200 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.

Geologically the name refers to the continued expansion of platform covers during this period. In the early Ectasian period, a day was 17 hours and 32 minutes. At the end of the Ectasian, it was 18 hours and 28 minutes.

This period is interesting for the first evidence of sexual reproduction. The 1.2 billion years old Hunting Formation on Somerset Island, Canada , dates from the end of the Ectasian. It contains the microfossils of the multicellular filaments of Bangiomorpha pubescens (type of red algae), the first taxonomically resolved eukaryote. This was the first organism that exhibited sexual reproduction, which is an essential feature for complex multicellularity. Complex multicellularity is different from "simple" multicellularity, such as colonies of organisms living together. True multicellular organisms contain cells that are specialized for different functions. This is, in fact, an essential feature of sexual reproduction as well, since the male and female gametes are specialized cells. Organisms that reproduce sexually must solve the problem of generating an entire organism from just the germ cells.

Sexual reproduction and the ability of gametes to develop into an organism are the necessary antecedents to true multicellularity. In fact, we tend to think of sexual reproduction and true multicellularity as occurring at the same time, and true multicellularity is often taken as a marker for sexual reproduction.

See also

• Earth:Boring Billion – Earth history, 1.8 to 0.8 billion years ago
• Earth:Jotnian – Oldest known sediments in the Baltic area that have not been subject to metamorphism
• Earth:Riphean (stage)

References

• "Mesoproterozoic Era". essayweb.net. http://essayweb.net/geology/timeline/mesoproterozoic.shtml. 
• James G. Ogg (2004). "Status on Divisions of the International Geologic Time Scale". Lethaia 37 (2): 183–199. doi:10.1080/00241160410006492.