Types of time scales
TimeAbstract
Geochronometric scales
Conclusions
Albian
Aalenian
Artinskian
Arenigian
Middle Ages
Han Dynasty
Satavahana Dynasty
476 AD – 1453 AD
206 BC – 220 AD
200 BC – 236 AD
~ 105 Ma
~ 180 Ma
~ 260 Ma
~ 480 Ma
Partitioning timeNominal and interval scales
Content Events Time
0
100
200
300
400
500
600
700
Time
0
100
200
300
400
500
600
700
Geon (H.P. Woodward, 1929, Pan -Amer. Geol. 51:15-22)
A unit … “taken to represent eitherthe span of the average geologic period,or the thickness of the averagestratigraphic equivalent, a matterof 60,000,000 years, and 50,000 feet[~15 km] of clastic depositions”
Using 543 Ma for the base of the Cambrian,and 11 geologic periods, an updated
value for Woodward’s geon is ~49.4 my
Complex nomenclature
JIN et al., 1991(Jour. of Stratigraphy 15(4):313-315, 320)
Scheme based onequal time intervals,
but with complex nomenclature
and inconsistent divisions:
Units have 3 divisions for300-my eras in Proterozoic,2 divisions for 400-my eras
in Archean
JIN et al., 1991(Jour. of Stratigraphy 15(4):313-315, 320)
Scheme based onequal time intervals,
but with complex nomenclature
and inconsistent divisions:
Units have 3 divisions for300-my eras in Proterozoic,2 divisions for 400-my eras
in Archean
Geon (geological eon) (Hofmann, 1990)
A specified 100-million-year intervalof geologic time, counted backwardfrom the present.
The geon is named for the leftmostpart of the number representing age.
Ages such as 1851 Ma and 1800 Ma belong to Geon 18;the Cretaceous extinction (065 Ma) belongs to Geon 0
Implications
Period/system boundaries approximategeon boundaries
Era/erathem boundaries lie near middle of geons
Parallel, complementary scales
100-my bins (Geon units)
Grenville Province
Metasediments
Time slice maps
Sediments
-- -- -- Inferred SE extent of Laurentiaat end of Geon 16
-- -- -- Inferred SE extent of Laurentiaat end of Geon 14
Sedimentary sequences
Sediments
Temporal classification of principal tectonic elements adjacent to the Slave craton
Hoffman & Hall, 1993, GSC Open File 2559
Geologic map using geon units
Geon gap map
Planetary histories and correlation
Perspectives
Scale of phenomena(adapted from Carey 1962, J. Geol. Soc. India 3:97-105)
H.J. Hofmann, Dept. of Earth and Planetary Sciences, and Redpath Museum, McGill University, Montreal, QC H3A 2A7 [email protected]
Eons and geons - a simple planetary time scale
A widely used dictionary defines a time scale as "an arrangement of events used as a measure of the relative or absolute duration or antiquity of a period of history or geologic or cosmic time..." (Gove,1986, p. 2395). Different types of scales exist: in increasing order of information content, these are binary, nominal, ordinal, interval, and ratio scales. The Phanerozoic time scale has divisions based on characteristic fossil content and has nominal and ordinal attributes; its chronostratigraphic units are defined at stratotypes, and they are of relative short duration and most have been calibrated radiometrically. The divisions of the Proterozoic time scale proposed by the International Commission on Stratigraphy (Cowie et al., 1989) are of relatively long duration, and are named after geohistorical content and thus viewed as corresponding to chronostratigraphic units; yet, contrary to rules of stratigraphic nomenclature, they are not based on designated stratotypes, but on arbitrary ages with large round numbers.
For overview and integrative studies of planetary evolution during the longest part of Earth history (the Cryptozoic or Precambrian), a universal calendar system with numerical units of appropriately long duration to encompass major geological developments (basin formation, orogenic belts, etc.) is more suitable. A convenient measure of such a geochronometric scale is a unit of 100 million years (geon). Such a simple, numerical, equal-interval scale, coupled with a corresponding simple nomenclature (Hofmann, 1990, 1992, 1999), is preferable and more efficient in conveying long-term evolutionary trends than a system of complex nomenclature (Cowie et al., 1989; Plumb, 1991, 1992). The geon concept has been applied to document the geotectonic development of some regions, such as northwestern Canada, and the Grenville Province, and various authors have long used 100-m.y. bins in compilations illustrating various aspects of geospheric evolution.
In addition to geon unit maps, the geon concept can also be used in the preparation of geon gap maps, which emphasize the time values of contacts or discontinuities between major rock units, by visually and quantitatively portraying their relative magnitude. Such maps may be useful, for example, in the exploration for unconformity-related ore deposits.
8A universal geon interval scale for numerically specified time periods of long duration (bins of 10 a) affords manifold advantages; in essence, such a scale has the benefits of being:1) numerical, direct, and simple, with intervals of equal duration;2) easy to learn, to remember, and to apply, because the numeral part also provides the nominal and ordinal functions - only 1 word needs to be assimilated, instead of necessitating the learning of a multitude of names whose additional requirement is that relative positions also need to be remembered;3) geopolitically neutral by transcending language barriers and jurisdictional boundaries;4) a logical extension of the calendar system;5) versatile, and facilitating quantitative studies by providing 46 suitable time slices of equal duration in the preparation of certain maps, sections, and graphs tracking the evolution of the geospheres for all of geologic history;6) applicable beyond Earth; and7) helpful in enhancing communication with non-geologists by obviating a series of complex names of units, and by taking advantage of the early-acquired ability to count.
Precambrian chronologic data span most of geologic time and are dominantly numeric, so why not also utilize a numerical classification and a matching ordinal nomenclature? Astronomers already employ light-year and parsec units for large distances, so it is entirely appropriate to adopt a scale for correspondingly long geologic and astronomic time intervals.
References:
Cowie, J.W., Ziegler, W., and Remane, J., 1989, Stratigraphic Commission accelerates progress, 1984 to 1989. Episodes, v. 12 (2), p. 79-83.Gove, P.B. (Editor-in-chief), 1986, Webster’s third new international dictionary of the English language, unabridged. Springfield, MA, Merriam-Webster Inc., 2663 p.Hofmann, H.J., 1990, Precambrian time units and nomenclature - the geon concept: Geology, v. 18, p. 340-341.Hofmann, H.J., 1992, New Precambrian time scale: comments. Episodes, v. 15 (2), p. 122-123.Hofmann, H.J., 1999, Geons and geons. Geology, v. 27, p. 855-856.Plumb, K.A., 1991, New Precambrian time scale. Episodes, v. 14, p. 139-140.Plumb, K.A., 1992, New Precambrian time scale: reply. Episodes, v. 15 (2), p. 124-125.
Concepts of time
•
Period, duration•
Point, occasion, event
• Tempo
• Irreversibility
Some applications
seconds
10
104
5
km
km
103 km
102 km
10 km
1 km
102101
100 m
10 m
1 m106104 108 1010 10141012 1016
geonhour day year Masec min ka Ga
Organisms
Gla
ciers
s
Mounta
in b
lte
Sed. basi
ns
As
robl
ms
t
ee
Use a universal calendar system with numerical units appropriately large to encompass major geological developments (basin formation, orogenic belts,
evolution, etc.). A convenient measure is a unit of 100 million years.
Why use the Geon concept?
Geons for the Precambrian!
It is numerical, direct, and simpleIt is easy to learn, remember, and applyIt is necessary to learn only 1 wordIt transcends language barriersIt is geopolitically neutralIt is a logical extension of the calendar systemIt provides time slices of equal durationIt is versatile and facilitates quantitative studiesIt is applicable beyond EarthIt is helpful in communicating with non-geologists
Precambrian chronologic data are dominantly numeric.
Then, why not utilize chronometric divisions with a corresponding numeric nomenclature?
Astronomers use light-year and parsec for large distances; it thus is appropriate to have a name for long time intervals
Clocks
Universal time (UT): Earth’s rotation with respect to Sun solar (synodic) day = 24h = 86,400s
Ephemeris time: Motion with respect to distant star sidereal day = 23h 56.1m = 86,164s
Atomic time:133 emission frequency of Cs 9,192,631,770/s
21
18
6
www.eps.mcgill.ca/~hofmann/geonscale.html
Terminal Proteroz. (Vendian/ Ediac.)
Cryogenian
Tonian
Stenian
Ectasian
Calymmian
Statherian
Orosirian
Rhyacian
Siderian
CENOZOIC
MESOZOIC
PALEOZOIC
NEOPROTEROZOIC
MESOPROTEROZOIC
PALEOPROTEROZOIC
NEOARCHEAN
PHANERO-ZOIC
PROTEROZOIC
ARCHEAN
CR
YP
TO
ZO
IC
(PR
EC
AM
BR
IAN
)
TIMEmill ions of years
HADEAN
EON ERA
Oldest invertebrates
Oldest dated terrestrial rocks
Oldest dated terrestrial minerals
Oldest microfossils, stromatolites
Oldest carbonate platforms
Oldest cyanobacterial biomarkers
Glaciations
Martian dubiofossils (ALH84001)
Oldest macrofossilsSudbury astrobleme
(Grypania)
4000
3000
2000
2500
1600
1000
~543
250
65
Ma
MESOARCHEAN
PALEOARCHEAN
EOARCHEAN
3600
2800
3200
Dinosaur extinction, oldest primates
Permian extinctionOldest repti les
Oldest birds, mammals, angiosperms
Cambrian explosion
Oldest chemofossils
Origin of Earth; oldest meteorites
Selected benchmarks
Oldest red algae
Oldest eucaryotic biomarkers
Oldest f ishes
Oldest amphibians
Oldest green algae
0 CretaceousJurassicTriassicPermianCarboniferousDevonianSilurianOrdovicianCambrian
NeogenePaleogene
Period,System
1000
GEON
(after Hofmann, 1990, 1992; 2000 - Geolog, v. 29, pt. 1, p. 18 )
Geologic scale - geon scale
Preston E. Cloud, Jr.1912-1991
Opinion
Rivers, 1997, Prec. Res. 86:117-154
17
26
10
Condie, 1997, Plate Tectonics and Crustal Evolution
Geon map units(after Hofmann, 1990, 1992)
Phanerozoic
Proterozoic
Archean
GEON
Geon map units and gaps
GEON HIATUS
Phanerozoic
Proterozoic
Archean
Phanerozoic
Proterozoic
Archean
40 00
30 00
20 00
0123456789
101112131415161718192021222324
2625
27282930313233343536373839404142434445
0
10 00
GEONMa Time-rock
1
34
11-10
12
161718
20-19
29-26
5
39
HJH 03
Geon Scale
TIMEmill ions
of years
Ga
LUNAR TIME SCALE MARTIAN TIME SCALE
HJH 03
Selected events Selected eventsPeriod,System GEON
ALH84001dubiofossils
ALH84001impact
ALH84001pyroxenite
4.1
3.9
3.2
1.1
Copernican
Eratosthenian
Late
Late
Early
Early
Early
Late
Middle
Middle
Imbrian
Nectarian
Pre-Nectarian
Copernicus
Tycho
? Eratosthenes
Major basins(CrisiumSerenitatisTranquilitatisetc.)
Imbrium Basin
Imbrium Lavas
Orientale Basin
(Murray et al., 1981) (Cattermole, 1992)
Hesperian
Amazonian
Noachian
4000
3000
2000
1000
0123456789
101112131415161718192021222324
2625
27282930313233343536373839404142434445
0
Time + rocks
SCALES
binary
nominal
ordinal
interval
ratio
EXAMPLE
limit
stratigraphic unit
stratigraphic succession
geochronometry
absolute zero
evolution
event
-10 -5 0
Carbonif. Cret.
Tertiary Quat.
pre- post-
0
Time
SCALES ASPECTS
binary
nominal
ordinal
interval
ratio
instant, event
age, quality
chronologic
duration, arbitrary zero
absolute zero (no -ve)
evolution, change
-10 -5 0
0
present
1 2 3 4
past future
infancy old age
Cambrian
TPS (Ediacaran)
Silurian
Ordovician
Carboniferous
Devonian
Triassic
Permian
L. Cretaceous
Jurassic
Neogene, Paleogene
U. Cretaceous
Cambrian
TPS (Ediacaran)
Silurian
Ordovician
Carboniferous
Devonian
Triassic
Permian
L. Cretaceous
Jurassic
Neogene, Paleogene,
U. Cretaceous
Comparing Phanerozoic system and geon boundaries
Period
0
1
2
3
4
5
Geon
0
1
2
3
4
5
GeonAge*
1.1
5.7
0
10
10
10
* Ma
1.1
5.7
0
10
10
10
Ma
* after Okulitch 1995, GSC Open File 3040
98.9 Ma
205.7 Ma
300 Ma
410 Ma
510 Ma
590 Ma
0 Ma
0123456789
101112131415161718192021222324
2625
27282930313233343536373839404142434445
Complex nomenclature
GOLDICH, 1968(Can. J. Earth Sci. 5:715-724)
Scheme based onequal time intervals,
but with complexalphanumeric nomenclature:
Greek letter units ascendingwith increasing age;
numbered units decreasingwith increasing age
GOLDICH, 1968(Can. J. Earth Sci. 5:715-724)
Scheme based onequal time intervals,
but with complexalphanumeric nomenclature:
Greek letter units ascendingwith increasing age;
numbered units decreasingwith increasing age
4321
Comparisons
100 a = 1 a = 1 year101 a = 1 decade102 a = 1 century103 a = 1 ka = 1 milennium106 a = 1 Ma = 1 megennium108 a = 1 geon109 a = 1 Ga = 1 gigennium
Numerical nomenclature
Units of 108 years previously considered
100 my, Ma - current geological literature(i nien) - Chinese geological literature
megacentury - A.F. Trendall, 1966becquerel - P.F. Hoffman, unpublishedgeocentury - P.E. Cloud, 1988geon - H.J. Hofmann, 1990
PRIMITIVE POZOIC
ROT
PROZOCI PO IC
HY ZO IC
EOZO
ARCHAEOZOIC
HURONI NAALGONKIAN
AGNOZ I
TO O C
GE
OG
EN
ICP
RIS
CO
AN
CRYPTOZOIC
COLLOZOIC
AZOIC
EAR Y PR CAMBRIAN
L E
MIDDLE PRECAMBRIAN LATE PRECAMBRIAN
PROTEROZOIC
EOMORPHIC
EPEIROPHYTIC
SIC
THALAS OPHYT
HA
DE
AN
EOBIOTICPROGONIC
PROGONOZOIC
LIPOZOIC
ARCEAH
N
RIPHEAN VENDIAN APHEBIAN HELIKIAN HADRYNIAN
PROTERYTI
OPHC
KEEWATIN
Terminology jungleth(after Hofmann, 1972, Int. Geol. Cong., 24 Sess., Proc. Sect. 1, p. 20-30)
HJH 00
Geon 5
Geons18-16
Geons11-10
Geon 3
Geon 2
Graphic representation of record
fit time to rock sequence
Thickness
Spatial section
fit rocks into time scale
Time
Time section
fit rocks into time scale
Time
Time section
Concepts
Rocks + gapsgaps
A B C D E F G H I J K L M N O P Q R S
Chronostrat.record
Sections
incomplete, discontinuousregionalregional
continuous, uniformuniversaluniversal
TimeTime
bins
Age distribution of continental crust
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