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Geological timescale (地質年代)






Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

[ era | chronology | extinction event | fossil 化石 ]

索引

Paleobotany (古植物学)

Late 19 c: Advance in Europe (esp., German) → established
Early 20 c: Advance the techniques of microscope and thin section → introduced to Japan

Objectives

Paleobotany = botany + geology

  1. flora, distribution, vegetation, and the succession
  2. paleoecology and paleoclimate
  3. phylogeny → plate tectonics (background)
major Subjects
  1. Precambrian (先カンブリア) = beginning of life on earth
  2. Beginning of terrestrial plants = evolution of terrestrial plants
  3. Evolution of seed plants (esp., angiosperms)

The evoltion of plants and plants does not always occur togehter. In gereranl, plants evolve slightly earlier than animals, probably because of food chains.

Era ()


The Geologic Time Scale is an artificial division of the continuous history of the planet. Divisions are based mainly on changes in life. Divisions between Periods are often associated with major events such as extinction.
The boundaries are real places to geologists. The Proterozoic-Cambrian boundary is marked at a remote spot in a cliff face on the Burin Peninsula, Newfoundland where the change in fossil life marks the beginning of the Cambrian. It is placed between the appearance of the Ediacaran fauna and the first appearance of trilobites. Within this time span of 30-50 million years, the boundary is recognized by the appearance of small shelly fossils. Other fossil markers include the first appearance of worm tubes, called sabelliditids, various kinds of trace fossils and the later appearance of trilobites.

(St John Museum. Sept 19 2014)

Cainozoic (新生代)
Mesozoic (中生代)
Paleozoic (古生代)
Proterozoic (原生代)
Chronology (年代学)

Cainozoic (新生代)


> 65 million-present

Quaternary (第四紀)

Holocene (完新世): 0.0117–0 (Ma)

Jomon forest, Jomon man

Jomon marine transgression (縄文海進)
7000-4000 YBP (peak = 6500-600 YBP)
= Holocene glacial retreat
Warm period (1-2°C > at present) → 2-3 m a.s.l. > at present
Pleistocene (更新世): 0.126–2.58
Tarantian タランチアン: 0.126–0.0117
Ionian イオニアン: 0.781–0.126
Calabrian カラブリアン: 1.80–0.781
Gelasian ゲラシアン: 2.58–1.80

Tertiary (第三紀)

Neogene (新第三紀)
23-258 million
Pliocene (鮮新世)
Miocene (中新世)
Paleogene (古第三紀)
The age of mammals (哺乳類)
Oligocene (漸新世)
Eocene (始新世)
Palaeocene (晩新世)

Mesozoic (中生代)


250-65 million

Cretaceous (白亜紀)
Cretaceous–Paleogene boundary
145-65 Mya
warm climate → high eustatic sea levels
Jurassic (ジュラ紀)
Triassic (三畳紀)

Paleozoic (古生代)


544-250 million (Wegener 1912)
Gondwana
Gondwana·Laurasia [200 myr]
Pangea was separated into two continents, Laurasia and Gondwana
Pangaea
Pangaea [230 myr]
Permian (二畳紀/ペルム紀)
299–252 Mya (million years ago)
The world was dominated by two continents, Pangaea and Siberia, surrounded by a global ocean, Panthalassa.
Carboniferous (石炭紀)
Devonian (デボン紀)
Silurian (シルリア紀)
= Gotlandian + Ordovician
Gotlandian (ゴトランド紀)
Ordovician (オルドビス紀)
Cambrian (カンブリア紀)
Sigillaria were important trees in the late Pennsylvanian forest. They were smaller than some of the other lycopods, growing about 20 to 30 meters tall. The bark of fossil Sigillaria is easy to recognize. Unlike the other common lycopod, Lepidodendron, leaf scars of Sigillaria appear to be arranged in vertical rows. All of the lycopod trees, except for Sigillaria, became extinct before the end of the Pennsylvanian Period.

(St John Museum, Sept 19 2014)

Lycopod trees like Lepidodendron dominated the lowlands during the Pennsylvanian Period. They were large, growing to more than 50 meters tall with a trunk 1 to 2 meters in diameter. The “root” system extended as far as 12 meters into the floor of the swamps where they grew. The bark of Lepidodendron-like trees is easy to recognize. The spiral, diamond-shaped pattern shows where leaves were attached to the trunk and brnaches.
Although the name Lepidodendron is used for the entire tree. The parts of large trees are usually found separated from other parts of the tree. Detached roots, leaves, cones and spores have all been given separate names. Detached roots are known by the name Stigmaria. These fossils are often found in clay, believed to be soil in which the trees grew. The overlying coal layer represents the decayed and compressed swamp vegetation. Detached leaves are sometimes called Cyperites, while cones are known as Lepidostrobus.

(St John Museum, Sept 19 2014)

The most important swamp trees were lycopods, Lepidodendron and Sigillaria. Today lycopods in New Brunswick are represented by tiny plants, but more than 300 million years ago Lepidodendron grew more than 50 meters tall. During most of the Pennsylvanian Period Lepidodendron-like trees made up eighty percent of the forest. As the Earth’s climate swung from wet to dry, the forest composition changed too. During a second dry interval in the late Pennsylvanian most of the lycopods became extinct, and were replaced by ferns.
Coal deposits, characterized the Pennsylvanian Period, deposited mostly in lowland swamps where fallen tree trunks accumulated in large numbers. Fossilized roots of Lepidodendron are often found in clay soils, believed to have been the bottom of the Pennsylvanian swamps. Overlying coals represent the decayed and compressed swamp vegetation. Some layers even show evidence of ancient forest fires (森林火災).

(St John Museum, Sept 19 2014)

Proterozoic (原生代)


2.5 billion-542 million
just before the proliferation of complex life on Earth
1.9 billion: first birth of continent

Neuna = North Europe and North America

1.8-1.5 billion: Columbia Continent (= Hudsonland)
1.5-1.0 billion: Pannotia
1.0-0.7 billion: Rodinia

Archaean, or Arcaheozoic (始生代, 太古代)

3.8(4.0)-2.5 billion
the Earth crust had cooled enough to allow the formation of continents

Hadean (冥王代)

= Pre-archean and Priscoan
The birth of earth to 3.8 billion

Planetary sicence (惑星科学)


≈ astronomy

The origin of the universe

BBT
Fig. Timeline of the metric expansion of space, where space (including hypothetical non-observable portions of the universe) is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch; and at the center, the expansion accelerates
Big bang theory, BB theory (ビッグバン理論)
All of the current and past matter in the universe came into existence at ≈ 13.8 billion years ago

(Sato 1981, Guth 1980)

Inflationary universe theory (インフレ宇宙論)

Astrobiology (宇宙生物学)

Fermi paradox (フェルミのパラドクス)
Drake equation (ドレイク方程式)
a probabilistic equation to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy

N = R*·fp·ne·fl·fi·fc·L

N = the number of civilizations in our galaxy with which communication might be possible
R* = the average rate of star formation in our galaxy
fp = the fraction of those stars that have planets
ne = the average number of planets that can potentially support life per star that has planets
fl = the fraction of planets that could support life that actually develop life at some point
fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations)
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L = the length of time for which such civilizations release detectable signals into space

R* ≈ 1-10 year-1
fp = 0.5 (tentative)
ne = 1 (e.g., the solar system has Earth = 1)
fl, fi and fc = 1, respectively (optimistic assumption)
L = not determined (controversial)

L is the most important factor to determine N

When L = 1 million years, N = 5 million

Chronology (年代学)


Etymology
chronos (Gr. χρóνς, time) + (Gr. -logica, λογíα, logics)
Definition
The determination of the temporal sequence of past events

chronology of planets
chronology of succession
chronology of volcanic eruptions
chronology of seedbank

Direct measurement of seedbank age

Abstract. We describe a new approach to determining the age structure of seed banks of natural plant populations and apply it to a natural population of the Sonoran Desert winter annual, Pectocarya recurvata (Boraginaceae). Unlike other 14C techniques, tandem accelerator mass spectrometry (TAMS) counts the number of carbon isotope atoms, permitting high precision with small samples. Aboveground nuclear bomb tests caused atmospheric 14C levels to peak in 1963. Their subsequent gradual decline provides a signal for aging seed banks with TAMS. We constructed a calibration curve using seeds with known dates of production during 1980.1995, then used it to age 53 seeds sampled from a natural seed bank in 1993, at the Desert Laboratory in Tucson, Arizona. Seed number declined with age at an approximately exponential rate, with the oldest recovered seed having an estimated age of 5 yr (95% CI = ± 2.3 yr). The seed bank age structure was judged more than adequate to buffer this population from typical fluctuations, based on an examination of 15 yr of population dynamic data. The TAMS technique has strong potential for answering a broad range of ecological and evolutionary questions requiring post-1963 age determinations and for which a several-year confidence interval is acceptable.

(Moriuchi et al. 2000)

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