Cretaceous-Tertiary boundary
- Cretaceous-Tertiary boundary
- Cretaceous-Tertiary boundary Cre*ta"ceous-Tert"i*ar*y
boun"da*ry (kr[-e]*t[=a]"sh[u^]s), n.
a thin layer of geologic deposits, of varying thickness in
different parts of the world, found between the geological
strata identified as Cretaceous and the strata above,
identified as Tertiary; also, the time point or period
marking the boundary between the Cretaceous and Tertiary
periods.
Syn: K/T boundary.
[PJC]
Note: According to a theory gaining acceptance (as of 1997),
these deposits were formed as the debris of a large
comet or meteorite impact on the earth, which threw up
a large quantity of dust into the atmosphere, causing
profound though temporary climatic change, and caused
or hastened the extinction of numerous species,
including the dinosaurs. This hypothesis was first
postulated by Luis and Walter Alvarez on the basis of
an excess of iridium found in the boundary layer, and
was later supported by additional evidence of various
types. The impact is believed to have occurred at the
edge of the Yucatan peninsula in Mexico, forming what
is termed the Chicxulub crater, which is partly under
the Gulf of Mexico, is not evident from surface
topography, and was detected primarily by gravity
anomaly readings and subsurface geological
characteristics.
[PJC]
The Collaborative International Dictionary of English.
2000.
Look at other dictionaries:
Cretaceous - Tertiary boundary — … Useful english dictionary
Cretaceous–Tertiary extinction event — Artist s rendering of bolide impact Badlands nea … Wikipedia
Cretaceous — Period 145.5–65.5 million years ago … Wikipedia
Tertiary Period — Interval of geologic time, 65–1. 8 million years ago. It constitutes the first of the two periods of the Cenozoic Era, the second being the Quaternary. The Tertiary has five subdivisions: (from oldest to youngest) the Paleocene, Eocene, Oligocene … Universalium
Cretaceous Terrestrial Revolution — The Cretaceous Terrestrial Revolution (abbreviated KTR) describes the intense diversification of angiosperms, insects, reptiles, birds, and mammals during the Middle to Late Cretaceous.[1] Before the paper described the KTR, it had been widely… … Wikipedia
K–T boundary — The K T boundary is a geological signature, usually a thin band, dated to 65.5 ± 0.3 (mya). [ [http://www.stratigraphy.org/cheu.pdf International commission for Stratigraphy] ] K is the traditional abbreviation for the Cretaceous Period, and T is … Wikipedia
Cretaceous Period — Interval of geologic time from с 144 to 65 million years ago. During the Cretaceous the climate was warmer than today. In the seas, marine invertebrates flourished, and bony fishes evolved. On land, flowering plants arose, and insects, bees in… … Universalium
Late Cretaceous — (100mya 65mya) refers to the second half of the Cretaceous Period, named after the famous white chalk cliffs of southern England, which date from this time. Rocks deposited during the Late Cretaceous Period are referred to as the Upper Cretaceous … Wikipedia
K-T boundary — noun Etymology: K (alternative for C as abbreviation for Cretaceous) + Tertiary Date: 1983 the transition between the Cretaceous and Tertiary periods of geologic time characterized by a mass extinction of many forms of life including the… … New Collegiate Dictionary
k-t boundary — noun Usage: usually capitalized K&T Etymology: K (alternative for C as abbreviation for Cretaceous) + Tertiary : the transition between the Cretaceous and Tertiary periods of geologic time characterized by a mass extinction of many forms of life… … Useful english dictionary
