FTa8 FTa10

n=19

n=8 mean value

0.011

0.114

Fig. 24. Apatite and zircon grains of FTa8 and FTa10. Black number with under line indicates apaitite grain and grey number indicates zircon grain. A histograms of chlorine concentration (wt%) with WDS-EPMA (JXA-8900) from apatite grains show these photos.

Individual apatite grains were measured two points on polished

grains and averages of two values were regarded as grain values.

ኳ↛᮲௳࡛ࡣ୍⯡࡟ሷ⣲㸦Cl㸧ࢆ0.0㹼2.0 wt㸣㸦㔜㔞ࣃ࣮ࢭࣥࢺ㸧࡯࡝ྵࢇ࡛࠸ࡿ㸬ࡑࡇ

࡛㸪ᮏ◊✲࡛࢔ࣃࢱ࢖ࢺFTᖺ௦ࢆ ᐃࡋࡓ2ヨᩱ࡟ࡘ࠸࡚㸪ሷ⣲⃰ᗘࡀ㛢㙐 ᗘ࡟ᙳ㡪ࡋ

࡚࠸ࡿྍ⬟ᛶࢆ᳨ウࡋࡓ㸬୧ヨᩱ࡟ྵࡲࢀ࡚࠸ࡿࡢࡣ㸪ⅆᡂᒾ⏤᮶ࡢ࢔ࣃࢱ࢖ࢺ࡛࠶ࡿࡓ

ࡵ㸪ᖺ௦ࢆ ᐃࡋࡓ⢏Ꮚ⮬యࡢሷ⣲⃰ᗘࢆಶࠎ࡟ ᐃࡍࡿᚲせࡣ࡞࠸࡜ุ᩿ࡉࢀࡿ㸦኱ᖹ

࡯࠿, 2005㸧㸬ࡑࡢࡓࡵ㸪ᖺ௦ ᐃࢆ⾜ࡗࡓࡢ࡜ྠ୍ࡢ㖔≀ศ㞳ヨᩱࡢ୰࠿ࡽ㸪࢔ࣃࢱ࢖ࢺ

ࢆ௵ព࡟㑅ูࡋ㸪ࡑࡢሷ⣲⃰ᗘࢆ ᐃࡋࡓ㸬 ᐃ࡟ࡣἼ㛗ศᩓᆺEPMA㸦JXA-8900㸸᪩✄

⏣኱Ꮫᆅ⌫⛉Ꮫᩍᐊ㸧ࢆ౑⏝ࡋࡓ㸬࢔ࣃࢱ࢖ࢺ⢏Ꮚࢆ࢚࣏࢟ࢩᶞ⬡࡟෭㛫࡛ᇙࡵ㎸ࢇ࡛㙾 㠃◊☻ࡋࡓᚋ࡟㸪 ᐃ᮲௳ࡣ15 kV㸪20 nA㸪ࣉ࣮ࣟࣈᚄ0 ȣm㸪ᶆ‽ヨᩱNaCl࡛ሷ⣲⃰

ᗘࢆᐃ㔞ࡋࡓ㸬Ἠ༡ὶ⣠ᒾ㢮ヨᩱ㸦FTa8㸧࡛ࡣ 19 ⢏Ꮚ㸦Fig. 24㸧㸪ᑼ࢔ࢲ࣓ࣟᒾヨᩱ

㸦FTa10㸧࡛ࡣ8⢏Ꮚ㸦Fig. 24㸧࡟ࡘ࠸࡚㸪ࡑࢀࡒࢀ1⢏Ꮚࡈ࡜࡟2࣏࢖ࣥࢺࡢ⃰ᗘ ᐃ

ࢆ⾜࠸㸪ᖹᆒ್ࢆྛ⢏Ꮚࡢሷ⣲⃰ᗘ࡜ࡋࡓ㸬⤖ᯝ㸪ሷ⣲⃰ᗘࡣἨ༡ὶ⣠ᒾ㢮ヨᩱ㸦FTa8㸧

࡛ࡣᖹᆒ0.114 wt%㸪ᑼ࢔ࢲ࣓ࣟᒾヨᩱ㸦FTa10㸧࡛ࡣᖹᆒ0.011 wt%࡛࠶ࡗࡓ㸦Fig. 24㸧㸬 ᮏ◊✲࡛ᢅࡗࡓ୧ヨᩱࡢ࢔ࣃࢱ࢖ࢺࡢሷ⣲⃰ᗘࡣపࡃ㸪Ketchamet 㸦1999㸧࡟ࡼࡾሷ⣲⃰

ᗘࡀ0.0 wt%࡛92Υ㸪0.4 wt㸣ࡢヨᩱ࡛95㹼100Υࡢ㛢㙐 ᗘࡀ♧ࡉࢀ࡚࠸ࡿࡇ࡜࠿ࡽ㸪

࢔ࣃࢱ࢖ࢺࡢ㛢㙐 ᗘ࡜ࡋ࡚ᮏ◊✲ࡀ᥇⏝ࡋࡓ100s20Υ㸦Wagner and Van den haute, 1992㸧ࡀጇᙜ࡞್࡛࠶ࡿࡇ࡜ࡀᨭᣢࡉࢀࡿ㸬௨ୖࡢ᮲௳࠿ࡽ㸪࿴Ἠᒙ⩌࡜ඹ࡟ᇙἐࡋࡓࡢ

࡞ࡽࡤ㸪FTa8ヨᩱࡢ࢔ࣃࢱ࢖ࢺFTᖺ௦ࡣ㸪ࣈࣟࢵࢡAす㒊ࡢ࿴Ἠᒙ⩌ࡢୖ᪼᫬ᮇ࣭ࡲࡓ ࡣࡑࢀ௨㝆ࡢ⿕⇕ᚋࡢ෭༷ࢆ♧ࡍ࡜⪃࠼ࡽࢀࡿ㸬ࡑࡢ᫬ᮇࡣ㸪ࣈࣟࢵࢡ A ᮾ㒊ࡢ࿴Ἠᒙ⩌

ୖ᪼᫬ᮇ㸦⣙66 Ma㸧࡜ㄗᕪ⠊ᅖ୍࡛⮴ࡍࡿ᫬ᮇ࡜࡞ࡿࡣࡎ࡛࠶ࡿࡀ㸪ᐇ㝿ࡣす㒊㸪Ng08 ᆅⅬࡢ࢝ࣜ㛗▼K–Arᖺ௦㸦65.8s2.8 Ma㸧࡜2Ȫࡢㄗᕪ⠊ᅖ࡛༊ูࡉࢀࡿ㸬ᚑࡗ࡚㸪ࣈࣟ

ࢵࢡA࡜␗࡞ࡾ㸪ࣈࣟࢵࢡBࡣ࿴Ἠሁ✚┅ỿ㝆᫬ࡢ⇕ⓗᙳ㡪ࢆཷࡅ࡚࠸࡞࠸࡜ゎ㔘࡛ࡁࡿ

㸦Fig. 21A㸧㸬ࡲࡓ㸪࿴Ἠᒣ⬦ᮾ㒊ᆅᇦ㸪ࣈࣟࢵࢡBࡢᑼ࢔ࢲ࣓ࣟᒾ࠿ࡽሗ࿌ࡉࢀࡓ࢝ࣜ

㛗▼ࡢK–Arᖺ௦72.9s4.6 Ma㸦76122802㸸ᰘ⏣࡯࠿, 1979㸧࡜㸪ࣈࣟࢵࢡA㸦Ng08㸪 Ng7ᆅⅬ㸧ࡢ࢝ࣜ㛗▼ࡢ୧K–Ar ᖺ௦ࡣ㸪2Ȫࡢㄗᕪ⠊ᅖࢆ⪃៖ࡋ࡚ࡶࡑࢀࡒࢀ0.3 m.y.㸪

1.1 m.y.ࡋ࠿㔜」ࡋ࡞࠸ࡇ࡜࠿ࡽࡶ㸪ࣈࣟࢵࢡA࡜ࣈࣟࢵࢡB࡛෭༷ྐࡀ␗࡞ࡿࡇ࡜ࡀᨭᣢ

ࡉࢀࡿ㸬ࣈࣟࢵࢡA࡜ࣈࣟࢵࢡBࡢቃ⏺᩿ᒙࡣ㸪㧗ゅࡢ༡ഴᩳ࡜᥎ᐃࡉࢀ࡚࠾ࡾ㸦㏆␥す 㒊MTL◊✲ࢢ࣮ࣝࣉ, 1981㸧㸪ࣈࣟࢵࢡAࡣṇ᩿ᒙ㐠ື࡛ࣈࣟࢵࢡB࡟ᑐࡋ㸪┦ᑐⓗ࡟ỿ 㝆ࡋࡓ࡜⪃࠼ࡽࢀࡿ㸬

ࣈࣟࢵࢡ B ࡟఩⨨ࡍࡿ㸪Ἠ༡ὶ⣠ᒾ㢮᭱ୗ㒊ࡢ㠀จ⅊㉁ሁ✚ᒾ㸦ഃᕝ♟ᒾ㸧ࡢࢪࣝࢥࣥ

FTᖺ௦㸦FTsb1㸸73.9s8.2 Ma㸧ࡣ㸪᭱ୖ㒊ࡢFTa8ࡢࢪࣝࢥࣥFTᖺ௦ࡼࡾ୰ኸ್ࡀ⣙

11 m.y.ⱝࡃ㸪⢏Ꮚᖺ௦ࡣ࢝࢖஧஌᳨ᐃ࡟ྜ᱁ࡋࡓ㸬๓㏙ࡢ㏻ࡾ㸪○ᒌࢪࣝࢥࣥ⢏Ꮚ࠿ࡽᵓ

ᡂࡉࢀࡿࡲࡓࡣࡑࢀࢆከࡃྵࡴሙྜ㸪FTࡀࣜࢭࢵࢺࡍࡿ⛬ᗘࡲ࡛෌ຍ⇕ࡉࢀ࡞࠸㝈ࡾ࢝࢖

஧஌᳨ᐃ࡟ྜ᱁ࡋ࡞࠸㸦᷄ཎ, 1997㸧㸬ࡼࡗ࡚ഃᕝ♟ᒾᒙࡀఱࡽ࠿ࡢ⇕ᙳ㡪࡛ZTAZ࡟㐩ࡍ

ࡿࡼ࠺࡞⿕⇕ࡢ⤖ᯝ㸪୍ᗘFTࡀ᏶඲࡟ཪࡣ࡯ࡰ᏶඲࡟ࣜࢭࢵࢺࡋࡓ࡜ゎ㔘ࡉࢀࡿ㸬ഃᕝ♟

ᒾᒙࢆྵࡴἨ༡ὶ⣠ᒾ㢮ࡢᮾ⦕㒊ࡀ㸪ࣈࣟࢵࢡ B ෆ࡛ᑼ࢔ࢲ࣓ࣟᒾ࡜᥋ࡋ࡚࠸ࡿࡇ࡜࠿

ࡽ㸪FTsb1ࡢࢪࣝࢥࣥFTᖺ௦ࡣ㸪ᑼ࢔ࢲ࣓ࣟᒾࡢ㈏ධ࡟ࡼࡿ⿕⇕㸦ᨻᒸ, 1982㸧ࡢᙳ㡪

ࢆཷࡅࡓྍ⬟ᛶࡀ♧၀ࡉࢀࡿ㸬ࡍ࡞ࢃࡕ㸪ࣈࣟࢵࢡB࡟࠾࠸࡚㸪90㹼85 Maࡈࢁ࡟ᄇฟࡋ ࡓἨ༡ὶ⣠ᒾ㢮ࡣ㸪74㹼72 Maࡲ࡛࡟ᮾ㒊࡛ᑼ࢔ࢲ࣓ࣟᒾࡢ㈏ධ࡟ࡼࡿ᥋ゐኚᡂࢆཷࡅ ࡓࡀ㸪ࡑࢀ௨㝆ࡣἨ༡ὶ⣠ᒾ㢮࡜ᑼ࢔ࢲ࣓ࣟᒾ࡟࢔ࣃࢱ࢖ࢺ FT ᖺ௦࠾ࡼࡧ࢝ࣜ㛗▼ࡢ K–Arᖺ௦࡟཯ᫎࡉࢀࡿ⛬ᗘࡢ⿕⇕࢖࣋ࣥࢺࡀ㉳ࡽ࡞࠿ࡗࡓ㸬ࡘࡲࡾ㸪ࣈࣟࢵࢡAࡢ࿴Ἠሁ

✚┅ࡢỿ㝆࣭ୖ᪼ࡀ㉳ࡗࡓ71㹼65 Maࡢ᫬ᮇ࡟㸪ࣈࣟࢵࢡBࡣ࡯࡜ࢇ࡝ᇙἐࡶୖ᪼ࡶࡋ࡞

࠿ࡗࡓ࡜⪃࠼ࡽࢀࡿ㸦Figs. 21A, 22㸧㸬ᮾ᪉࡯࡝ሁ✚┅ࡢᗏ㒊ࡀ㟢ฟࡍࡿ࡜⪃࠼ࡽࢀࡿ࿴Ἠ ᒣ⬦ᮾ㒊ᆅᇦ࡟ࡘ࠸࡚ࡣ㸪ሁ✚┅ᣑ኱᫬࡟ᙧᡂࡉࢀࡓᮾすᛶࡢ㝵ẁ≧᩿ᒙ⩌ࡀ㸪ࣈࣟࢵࢡA

࡜ࣈࣟࢵࢡBࡢ₞⛣ⓗቃ⏺࡜࡞ࡗ࡚࠸ࡿྍ⬟ᛶࡀ࠶ࡿ㸬Ng10ࡢ࢝ࣜ㛗▼ࡢK–Arᖺ௦࡟ࡘ

࠸࡚ࡣ㸪ࣈࣟࢵࢡ A ࠾ࡼࡧᚋ㏙ࡢࣈࣟࢵࢡB ࡛᥎ᐃࡉࢀࡿ෭༷᭤⥺࡟࠾࠸࡚㸪2Ȫࡢㄗᕪ

⠊ᅖ࡛ࣈࣟࢵࢡA㸪B ୧᪉ࡢ᭤⥺࡜㔜」ࡋ࡚࠸ࡿ㸬ࡑࡢࡓࡵ㸪ࣈࣟࢵࢡA㸪ࣈࣟࢵࢡB ࡢ

࡝ࡕࡽ࡟ᖐᒓࡍࡿྍ⬟ᛶࡶ⪃࠼ࡽࢀࡿࡀ㸪ᖺ௦ࡢ୰ኸ್ࡀ୧ࣈࣟࢵࢡࡢ෭༷᭤⥺ࡢ࡯ࡰ୰

㛫࡟఩⨨ࡍࡿࡓࡵ㸪₞⛣ቃ⏺࡟఩⨨ࡋ࡚࠸ࡿ࡜⪃࠼ࡿࡇ࡜ࡶྍ⬟࡛࠶ࡿ㸬࠸ࡎࢀ࡟ࡋ࡚ࡶ㸪 ᖺ௦ࡢㄗᕪ⠊ᅖෆ࡛࡝ࡢྍ⬟ᛶࡶ⪃៖ࡉࢀࡿࡓࡵ㸪ᮏ◊✲࡛ࡣ෭༷᭤⥺㸦Fig. 21A㸧࡟♧ࡋ

࡚࠸࡞࠸㸬ࡲࡓ㸪࿴Ἠᒣ⬦ᮾ㒊ࡢࣈࣟࢵࢡቃ⏺ࡢỴᐃ࡟ࡶ᭷ຠ࡛ࡣ࡞࠸㸬 㸲㸧ࣈࣟࢵࢡCࡢ⿕⇕࣭෭༷ྐ

ࣈࣟࢵࢡ C ࡟఩⨨ࡍࡿ㸪㏆ᮌᕝᆅᇦࡢᑼ࢔ࢲ࣓ࣟᒾ㸦FTa10㸧ࡢࢪࣝࢥࣥ࠾ࡼࡧ࢔ࣃ

ࢱ࢖ࢺFTᖺ௦ࡣ㸪ࡑࢀࡒࢀ67.8s5.4 Ma࡜50.0s6.6 Ma࡛࠶ࡿ㸬ᑼ࢔ࢲ࣓ࣟᒾࡢ㈏

ධ᫬ᮇࡣ࿴Ἠᒙ⩌ሁ✚㛤ጞ௨๓࡜ࡉࢀࡿ㸦ᒣ⏣┤฼࡯࠿, 1979㸧㸬ṇ☜࡞㈏ධ᫬ᮇࡣࢪࣝࢥ

ࣥU–Pbᖺ௦➼᳨࡛ウࡍࡿᚲせࡀ࠶ࡿࡔࢁ࠺ࡀ㸪ẚ㍑ⓗ㧗࠸㛢㙐 ᗘ㸦530s40Υ㸸Harrison and McDougall, 1980㸧ࡢᬑ㏻ゅ㛝▼ࡢK–Arᖺ௦86.8s8.6 Ma㸦Ng08㸸Shibata et al., 1994㸧࠾ࡼࡧ78.0s4.8 Ma㸦Ng10㸸ᰘ⏣࡯࠿, 2003㸧ࡀሗ࿌ࡉࢀ࡚࠸ࡿࡓࡵ㸪ࡼࡾ㛢㙐  ᗘࡢప࠸㯮㞼ẕࡢK–Arᖺ௦80.5s5.0 Ma㸦Ng08㸸Shibata et al., 1994㸧ࡶ⪃៖ࡍࡿ࡜㸪

ᑼ࢔ࢲ࣓ࣟᒾࡢ㈏ධ᫬ᮇࡣ㸪ᬑ㏻ゅ㛝▼ࡢK–Ar୧ᖺ௦ࡀ 2Ȫࡢㄗᕪ⠊ᅖ࡛㔜࡞ࡿ⣙ 80 Maࡼࡾྂ࠸࡜⪃࠼ࡽࢀࡿ㸬ࡼࡗ࡚㸪ഃᕝ♟ᒾᒙࡢࢪࣝࢥࣥFTᖺ௦㸦73.9s8.2 Ma㸧ࡣ㸪 ᮾ㒊ᆅᇦࡢᑼ࢔ࢲ࣓ࣟᒾࡢ㛢㙐 ᗘ௨ୗ࡬ࡢ෭༷᫬ᮇࢆ♧ࡍࡢࡔࢁ࠺㸬

ࢪࣝࢥࣥFTᖺ௦67.8s5.4 Maࡣ㸪ㄗᕪ⠊ᅖࢆ⪃៖ࡍࡿ࡜ᮏᆅᇦࡢ࿴Ἠᒙ⩌ࡢሁ✚㛤ጞ

┤๓࠿ࡽሁ✚⤊஢௨㝆࡟┦ᙜࡍࡿ㸬୍᪉㸪࢔ࣃࢱ࢖ࢺFTᖺ௦50.0s6.6 Maࡣ㸪ࣈࣟࢵࢡ Aࡢ࿴Ἠᒙ⩌ሁ✚ᖺ௦ࡼࡾ୰ኸ್ࡀ21 m.y. ⛬ⱝ࠸㸬ࡲࡓ㸪ࣈࣟࢵࢡAࡀୖ᪼࡟㌿ࡌࡓᖺ ௦ࢆ♧ࡍ࡜ゎ㔘ࡉࢀࡓᑼ࢔ࢲ࣓ࣟᒾࡢ࢝ࣜ㛗▼K–Arᖺ௦㸦ヨᩱNg08ࡢ65.8s2.8 Ma

࠾ࡼࡧNg7ࡢ65.2s4.0 Ma㸧࡜2Ȫࡢㄗᕪ⠊ᅖ࡛༊ูࡉࢀࡿ㸬᭦࡟㸪ࡇࡢ࢔ࣃࢱ࢖ࢺFT

ᖺ௦ࡣ㸪ࣈࣟࢵࢡBࡢἨ༡ὶ⣠ᒾ㢮ࡢ࢔ࣃࢱ࢖ࢺFTᖺ௦㸦80.0s11.2 Ma㸧ࡼࡾ୰ኸ್ࡀ

30 m.y. ⛬ⱝࡃ㸪2Ȫࡢㄗᕪ⠊ᅖ࡛༊ูࡉࢀࡿ㸬௨ୖࡢࡼ࠺࡟㸪ࣈࣟࢵࢡC ࡜ࣈࣟࢵࢡA㸪

B࡟ࡘ࠸࡚ࡶ㸪ὸᡤ࡛␗࡞ࡿୖ᪼ྐࢆ⤒ࡓ࡜ゎ㔘ࡉࢀࡿ㸦Figs. 21A, 22㸧㸬FTa10ᆅⅬ࿘㎶

ࡢ࿴Ἠᒙ⩌໭⦕㒊ࡢ⿕⇕ ᗘࡀ175㹼183Υ㸦Table 3㸧࡜ぢ✚ࡶࡽࢀ࡚࠸ࡿࡓࡵ㸪ࣈࣟࢵࢡ C ࡢᑼ࢔ࢲ࣓ࣟᒾ㸦FTa10㸧ࡀࣈࣟࢵࢡA ࡢ࿴Ἠᒙ⩌࡜ྠ᫬ᮇ࡟ྠ⛬ᗘỿ㝆ࡋࡓ࡜ࡋ࡚

ࡶZPAZ࡟฿㐩ࡏࡎ㸪ࢪࣝࢥࣥFTᖺ௦࡟ⱝ㏉ࡾࡣ⏕ࡌ࡞࠸㸬ࡍ࡞ࢃࡕ㸪FTa10ࡢࢪࣝࢥ

ࣥFTᖺ௦㸦67.8s5.4 Ma㸧ࡣ㸪ࣈࣟࢵࢡ C ࡢᑼ࢔ࢲ࣓ࣟᒾࡀ෭༷㐣⛬࡛ࢪࣝࢥࣥFT ᖺ௦ࡢ㛢㙐 ᗘ 240Υࢆึࡵ࡚ୗᅇࡗࡓ᫬ᮇࢆ♧ࡍ࡜ゎ㔘ࡉࢀࡿ㸬ࡑࡢࡓࡵ㸪ࣈࣟࢵࢡ C ࡢᑼ࢔ࢲ࣓ࣟᒾࡣ㸪ࣈࣟࢵࢡAࡢ࿴Ἠᒙ⩌࡜ྠ᫬ᮇ㸦67.8s5.4 Ma㸧ࡢᛴ㏿࡞ୖ᪼࡟క ࡗ࡚240Υ௨ୗࡲ࡛෭༷ࡉࢀ㸪50.0s6.6 Ma௨㝆࡟㟢ฟࣞ࣋ࣝ࡟㐩ࡋࡓ࡜࠸࠺ᆅྐࡀ⪃࠼

ࡽࢀࡿ㸬ࣈࣟࢵࢡB࡜ࡢቃ⏺᩿ᒙࡣ㸪㧗ゅࡢ໭ഴᩳ࡜᥎ᐃࡉࢀ࡚࠾ࡾ㸦ᨻᒸ, 1982㸧㸪ࣈࣟ

ࢵࢡCࡣࣈࣟࢵࢡB࡟ᑐࡋ࡚㏫᩿ᒙ㐠ື࡟ࡼࡾୖ᪼ࡋࡓ࡜⪃࠼ࡽࢀࡿ㸦Fig. 22㸧㸬 㸳㸧࿴Ἠᒣ⬦ᆅᇦࡢ࿴Ἠሁ✚┅ࡢⓎ㐩㐣⛬

࿴Ἠሁ✚┅ࡢ⦕㎶㒊࡟Ⓨ㐩ࡋࡓ᩿ᒙࡢ≉ᚩ࠿ࡽ㸪ሁ✚┅ࡢⓎ㐩ྐࢆ⪃ᐹࡍࡿ㸬࿴Ἠሁ✚

┅࡛ほᐹࡉࢀࡿഃ᪉࡬ࡢᛴ⃭࡞ᒾ┦ኚ໬㸪ሁ✚┅ෆ㒊࡛ࡢ〩᭤Ⓨ㐩㸪┤⥺ⓗ࡞ሁ✚┅⦕㒊 ቃ⏺ࡣ㸪ࣉࣝ࢔ࣃ࣮ࢺሁ✚┅ࡢ඾ᆺⓗ≉ᚩ࡜ࡋ࡚ᣲࡆࡽࢀ࡚࠸ࡿ㸦Crowell, 1974㸧㸬ࡉࡽ࡟㸪 ሁ✚┅㍈᪉ྥࡢ୍᪉ྥ࡟᫬௦ࡀⱝ໬ࡍࡿ࿴Ἠሁ✚┅ࡢ≉ᚩࡣ㸪㠀ᑐ⛠ࣉࣝ࢔ࣃ࣮ࢺሁ✚┅

ࡢRidge Basin㸦Crowell, 1982㸧࡜ඹ㏻ࡍࡿ㸬ࡼࡗ࡚㸪ᚑ᮶ከࡃࡢ◊✲⪅ࡀᨭᣢࡋ࡚ࡁࡓ

ࡼ࠺࡟㸦Miyata, 1990㸹ᒣ໭࣭ఀ⸨, 1999㸹Noda and Toshimitsu, 2009㸧㸪࿴Ἠሁ✚┅ࡣ

ࣉࣝ࢔ࣃ࣮ࢺሁ✚┅ࡢ୍ᙧែ࡛࠶ࢁ࠺㸬Shreurs and Colletta㸦1998㸧࡟ࡼࡿᶓࡎࢀᅽ⦰ሙ ࡢࣔࢹࣝᐇ㦂࡛ࡣ㸪ᇶ┙ࡢᶓࡎࢀ᪉ྥࡢࡦࡎࡳ㏿ᗘ࡜ࡑࢀ࡟┤஺ࡍࡿ᪉ྥࡢࡦࡎࡳ㏿ᗘࡢ ẚ࡛࠶ࡿࡦࡎࡳ㏿ᗘẚ ࡀ 3.6 ࡢሙྜࡣṇࡢⰼᘚᵓ㐀ࡀⓎ㐩ࡋ࡚㝯㉳ࡋ㸪7.3 ࡢሙྜࡣ඲య

ⓗ࡟ࡣ㝯㉳ࡶỿ㝆ࡶ⏕ࡌࡎᶓࡎࢀ᩿ᒙࡀ༟㉺ࡍࡿ㸬ࡘࡲࡾ㸪୍⯡ⓗ࡞ᶓࡎࢀᅽ⦰ሙ࡛ࡢሁ

✚┅ࡢỿ㝆ࡣ㸪ࡦࡎࡳ㏿ᗘẚࡀ኱ࡁ࠸ሙྜࡢࡳ⏕ࡌࡿ࡜⪃࠼ࡽࢀࡿࡓࡵ㸪ᶓࡎࢀሁ✚┅࡛

࠶ࡿ࿴Ἠሁ✚┅ࡢᙧᡂᛂຊሙࡣ㸪࡯ࡰ⣧ᶓࡎࢀሙࡲࡓࡣᶓࡎࢀᘬᙇሙࡢ࡝ࡕࡽ࠿࡛࠶ࡿ㸬

࿴Ἠᒙ⩌୺ศᕸᇦࡢ໭⦕࡟ἢࡗࡓ኱つᶍ᩿ᒙࡀ☜ㄆࡉࢀ࡞࠸ࡓࡵ㸪࿴Ἠሁ✚┅ࡣ୙㐃⥆࡞

᩿ᒙ⩌ࢆቃ࡟ỿ㝆ࡋࡓ࡜᥎ᐃࡉࢀࡿ㸬Wu et al.㸦2009㸧࡟ࡼࡿ࡜㸪ᶓࡎࢀᘬᙇሙ࡛Ⓨ㐩ࡋ

Early stage evolution Late-stage evolution

Less steep, concave-up en-echelon

faults

PDZ

PDZ

Cross-basin fault zone

Incipient planar fault

Hard-linked relay ramp

Predominantly oblique-extension Predominantly strike-slip PDZ

PDZ

Steep, planar en-echelon

faults

A

B

Wu et al. (2009)

Fig. 25. Transtensional pull-apart basins of natural conditions and

analogue modeling for sand box after Wu et al. (2009). (A) Transtensional

and pure pull-apart systems in the southern end of the Dead Sea fault

system. (B) Evolition of fault zone in a transtensional pull-apat basin

system. In the early stage, a narrow basin is formed between planar sub-

vertical en-echelon faults. In the late stage, soft- and hard-linked concave-

upward en-echelon faults and initiation of new planar faults are developed.

Fig. 26. Relationship between length of several pull-apart basin deposits and total thickness (modified after Hempton and Dunne, 1984). Total thckiness of Izumi sedimentary basin (ISB) in the Izumi Mountains referred to Miyata et al. (1994).

Thickness

Lenght of pullapart basin deposits 5

10 15 20 km

50 100 km

GB RB LB

CaBBB HuB DV

UCS

RB VB

ChB

DS HoB

ISB (in the Izumi Mountains)

㸦modified after Hempton and Dunne, 1984㸧

PB:Petrockstow Basin, LB:Lefors Basin BB:Bovey basin, RB:Ridge basin,

UCS: Upper Carboniferous basins of Spain, ChB:Chuckanut basin, Hob:Hornelen basin, VB:Vienna basin, GB:Glynnwye basin, HaB:Hanmer Plains basin, CaB:Carrington basin, HuB:Hulu basin, DV:Death Valley basin

Y=0.08x+0.26

ࡓࣉࣝ࢔ࣃ࣮ࢺሁ✚┅ࡢ⦕㎶㒊ࡣ㸪༢୍᩿ᒙ㠃࡛ࡣ࡞ࡃ୙㐃⥆࡟Ⓨ㐩ࡍࡿ㞜⾜≧ࡢ᩿ᒙ⩌

࡟ࡼࡾ⏬ࡉࢀ㸪ሁ✚┅እ⦕㒊ࡣࡑࡢỿ㝆ࡢᙳ㡪ࢆ࡯࡜ࢇ࡝ཷࡅ࡞࠸㸦Fig. 25A, B㸧㸬ࡇࡢ᩿

ᒙ⩌ࡀሁ✚┅Ⓨ㐩࡟కࡗ࡚┅ࡢෆഃࡢ㐠ືࢆ೵Ṇࡋ࡚እഃ࡟ᣑ኱ࡋࡓሙྜ㸪᩿ᒙ⩌࡟ᣳࡲ

ࢀࡿ⠊ᅖ࡟࠾࠸࡚ሁ✚≀࡜ᇶ┙ᒾࡢ୍㒊ࡣ୙ᩚྜ㛵ಀ࡜࡞ࡾ࠺ࡿ㸦Fig. 25A㸧㸬ࡲࡓ㸪ࡇࡢ

ࡼ࠺࡞᩿ᒙ⩌ࡣ㸪⣧⢋࡞ᶓࡎࢀ㐠ື࡛ᙧᡂࡉࢀࡓࣉࣝ࢔ࣃ࣮ࢺሁ✚┅࡛ࡣⓎ㐩ࡏࡎ㸪ᩳ஺

ศᒱ㐠ື㸦ᶓࡎࢀᘬᙇሙࡢࣉࣝ࢔ࣃ࣮ࢺࢩࢫࢸ࣒ࡸ㧗ゅࡢࣜࣇࢸ࢕ࣥࢢ㸧࡟ࡼࡿሁ✚┅ᙧ ᡂ࡛ࡋ࠿Ⓨ㐩ࡋ࡞࠸ࡇ࡜ࡀ♧၀ࡉࢀ࡚࠸ࡿ㸬ࡑࡢࡓࡵ㸪࿴Ἠሁ✚┅ࡣᶓࡎࢀᘬᙇሙࡢࡶ࡜

࡛Ⓨ㐩ࡋࡓࣉࣝ࢔ࣃ࣮ࢺሁ✚┅࡜ุ᩿ࡉࢀࡿ㸬ྠࡌᶓࡎࢀኚ఩㔞࡛ࡣ㸪ᶓࡎࢀᘬᙇሙ࡛Ⓨ

㐩ࡋࡓࣉࣝ࢔ࣃ࣮ࢺሁ✚┅ࡣ㸪⣧⢋࡞ᶓࡎࢀ࡛ࡢࣉࣝ࢔ࣃ࣮ࢺሁ✚┅࡜ẚ㍑ࡋ࡚㸪ሁ✚┅

ࡢつᶍࡀ኱ࡁࡃ࡞ࡿࡓࡵ㸦Wu et al., 2009㸧㸪࿴Ἠᒙ⩌ࡀ௚ࡢ௦⾲ⓗ࡞ࣉࣝ࢔ࣃ࣮ࢺሁ✚┅

ࡼࡾ኱ࡁ࡞✚⟬ᒙཌࢆ᭷ࡍࡿཎᅉࡢ୍ࡘ࡜࡞ࡗࡓྍ⬟ᛶࡀ࠶ࡿ㸦Fig. 26㸧㸬ᐇ㝿㸪Wu et al.

㸦2009㸧ࡀ⣧ᶓࡎࢀሙ࡜ᶓࡎࢀᘬᙇሙ࡛ᙧᡂࡋࡓሁ✚┅౛࡜ࡋ࡚♧ࡋࡓ୰ᮾࡢṚᾏ┅ᆅ࡜

࢔࢝ࣂ‴㸦Fig. 25A㸧ࢆẚ㍑ࡍࡿ࡜㸪Ṛᾏࡢ᭱῝㒊ࡀ⣙㸫700 㹫࡛┅ᆅࡢᖹᆒᶆ㧗ࡣ⣙㸫

200 m࠶ࡿࡀ㸪࢔࢝ࣂ‴ࡣ᭱῝㒊ࡀ㸫1850 㹫࡛ἢᓊࢆྵࡵࡓ⣙ 8๭ࡀ㸫800 㹫௨῝࡜㸪

ྠࡌ᩿ᒙ⣔࡟఩⨨ࡍࡿ࡟ࡶ࠿࠿ࢃࡽࡎᆅᙧⓗ≉ᚩࡀ኱ࡁࡃ␗࡞ࡿ㸦Ben-Avraham et al., 1979㸧㸬ሁ✚⎔ቃࡀ␗࡞ࡿࡓࡵ㸪ཝᐦ࡟ࡣሁ✚≀࡟ࡼࡿᇙ✚㏿ᗘࡢ㐪࠸ࡶຍ࿡ࡍࡿᚲせࡀ࠶

ࡿࡔࢁ࠺ࡀ㸪ỿ㝆㔞ࡀ኱ࡁࡃ␗࡞ࡿࡇ࡜ࡀࡇࡢᕪࡢ୺࡞せᅉ࡜⪃࠼ࡽࢀࡿ㸬

㏆␥ᆅ᪉ࡢⓑள⣖ᚋᮇࡢᗈᇦᛂຊሙࡣᶓࡎࢀᅽ⦰ᛂຊሙ࡜ࡉࢀ㸪࿴Ἠᒙ⩌ᙧᡂ࡟ࡘ࠸࡚

ࡶᶓࡎࢀᅽ⦰ᛂຊሙ࡛Ⓨ㐩ࡋࡓ࡜࠸࠺㆟ㄽࡀ࠶ࡿ㸦Okudaira et al., 2009㸧ࡀ㸪ୖグࡢቃ⏺

᩿ᒙ⩌ࡢ≉ᚩࡼࡾ࿴Ἠሁ✚┅ࡣᗈᇦᛂຊሙ࡜ࡣ␗࡞ࡿᒁᡤⓗ࡞ᶓࡎࢀᘬᙇሙ࡛Ⓨ㐩ࡋࡓࡶ

ࡢ࡜ぢࡽࢀࡿ㸬ࡑࡢࡼ࠺࡞౛࡜ࡋ࡚௨ୗ࡟஧ࡘࢆ♧ࡍ㸬Ratschbacher et al.㸦1989㸧ࡣ࢔

ࣝࣉࢫᮾ㒊ᆅᇦ࡟࠾࠸࡚㸪ᗈᇦᅽ⦰ሙ࡟Ꮡᅾࡋࡓ࡜⪃࠼ࡽࢀ࡚࠸ࡿᆅᇦⓗ࡞ᘬᙇሙࢆሗ࿌

ࡋ࡚࠾ࡾ㸪ࡑࡢཎᅉ࡜ࡋ࡚㸪ᆅẆࡢཌࡉࡢ⫧኱໬࡟ࡼࡿᆅẆࡢỿ㝆ࡲࡓࡣ኱㝣ᆅẆୗࡢᾏ ὒᆅẆࡀ࣐ࣥࢺࣝ࡬ỿࡳ㎸ࡴࡇ࡜࡟ࡼࡾⓎ⏕ࡋࡓᘬᙇሙ࡛࠶ࡿྍ⬟ᛶࢆ♧ࡋ࡚࠸ࡿ㸬ࡲࡓ㸪 Daczko et al.㸦2007㸧ࡣ㸪ࣉ࣮ࣞࢺ཰᮰ቃ⏺࡟఩⨨ࡋᶓࡎࢀᅽ⦰ሙ࡛ࡢୖ᪼ྐࢆࡶࡘ࣮࢜

ࢫࢺࣛࣜ࢔Ἀࡢ࣐ࢵࢥ࣮࣮ࣜᓥ࡟࠾࠸࡚㸪ᆅᇦⓗ࡞ᘬᙇሙࡀ༟㉺ࡋ࡚ാ࠸࡚࠸ࡿ࡜♧၀ࡉ

ࢀࡓཎᅉ࡜ࡋ࡚㸪㐣ཤࡢᾏᕊỿࡳ㎸ࡳ࡜‴᭤ࡋࡓࣉ࣮ࣞࢺቃ⏺࡟Ⓨ㐩ࡋࡓ↓ᩘࡢ㞜⾜ࢫࢸ

ࢵࣉࡀ㛵ಀࡋ࡚࠸ࡿ࡜⪃ᐹࡋ࡚࠸ࡿ㸬

࿴Ἠሁ✚┅ࡢୖ᪼᫬࡟㸪᩿ᒙ࠾ࡼࡧ୙ᩚྜ࡛⏬ࡉࢀࡿἨ༡ὶ⣠ᒾ㢮ࡀ࿴Ἠᒙ⩌࡜ඹ࡟ୖ

᪼ࡋࡓሙྜ㸪⌧ᅾ㟢ฟࡍࡿἨ༡ὶ⣠ᒾ㢮ࡣ㸪࿴Ἠᒙ⩌໭⦕㒊࡜ྠ⛬ᗘࡢ ATAZ ࢆ㉸࠼ࡿ⿕

⇕ࢆ⤒㦂ࡋ㸪ࡑࡢ࢔ࣃࢱ࢖ࢺFTᖺ௦ࡣ⤖ᒁࡢ࡜ࡇࢁ࿴Ἠᒙ⩌ୖ᪼᫬ᮇࢆ཯ᫎࡍࡿ࡜⪃࠼ࡽ

ࢀࡿ㸬࡜ࡇࢁࡀ㸪๓㏙ࡢࡼ࠺࡟㸪ヨᩱFTa8ࡢ࢔ࣃࢱ࢖ࢺFTᖺ௦ࡣ80.0s11.2 Ma࡛㸪࿴

Ἠᒙ⩌ୖ᪼᫬ᮇࢆ♧ࡍ࡜ࡣ⪃࠼ࡽࢀ࡞࠸㸬ࡑࡢࡓࡵ㸪ࡇࡢ࢔ࣃࢱ࢖ࢺFTᖺ௦ࢆゎ㔘ࡍࡿ࡟

ࡣ㸪ࣈࣟࢵࢡ B ഃ࡟኱つᶍ࡞ୖ᪼㐠ືࡀ⏕ࡌ࡚ࡣ࡞ࡽ࡞࠸ࡓࡵ㸪࿴Ἠሁ✚┅ࡢୖ᪼ࡢ㝿࡟

Ἠ༡ὶ⣠ᒾ㢮ࢆకࢃ࡞࠸ࡇ࡜ࡀᚲせ࡜࡞ࡿ㸬Arthur㸦1989㸧ࡣᶓࡎࢀᘬᙇሙ࠿ࡽᶓࡎࢀᅽ

⦰ሙ࡟ኚ໬ࡋࡓRhombᆺࣉࣝ࢔ࣃ࣮ࢺሁ✚┅࡟࠾࠸࡚㸪ỿ㝆ࡢ㝿࡟㐠ືࡋࡓሁ✚┅⦕㎶㒊 ࡢ᩿ᒙࡀ෌άືࡍࡿࡇ࡜࡛㸪௨๓ࡢሁ✚┅ࡢ୺ỿ㝆㒊ࡀ୍㌿ࡋ࡚ୖ᪼࡟㌿ࡎࡿⓎ㐩ྐࢆ♧

၀ࡋ࡚࠸ࡿ㸬࿴Ἠᒙ⩌㸦ࣈࣟࢵࢡA㸧࡜ᇶ┙ᒾ㸦ࣈࣟࢵࢡB㸧ࡢ⿕⇕࣭෭༷ྐࡣ㸪࿴Ἠᒣ⬦

ᆅᇦࡢ࿴Ἠሁ✚┅ࡀྠᵝ࡟㸪ሁ✚┅⦕㎶ࡢᇶ┙ᒾ࡜ࡣ⊂❧ࡋ࡚ୖ᪼࡟㌿ࡌࡓࡇ࡜ࢆ♧၀ࡍ

ࡿ㸬ලయⓗ࡟ࡣ㸪༡໭ᅽ⦰࡟ࡼࡾ㸪ࣈࣟࢵࢡ B ࡢ༡໭୧ഃࡢ᩿ᒙࡀ㏫᩿ᒙ࡜ࡋ࡚ࣈࣟࢵࢡ A࠾ࡼࡧࣈࣟࢵࢡ C ࡀୖ᪼ࡋࡓ࡜ࡍࢀࡤ࿴Ἠᒙ⩌ሁ✚௨㝆ࡢ෭༷ྐࢆㄝ࡛᫂ࡁࡿࡔࢁ࠺㸬 ᮏ◊✲࡛♧၀ࡉࢀࡓࡼ࠺࡞ᛴ㏿࡞ỿ㝆ᚋ࡟ࡍࡄ࡟⏕ࡌࡓẚ㍑ⓗ኱ࡁ࡞ୖ᪼ࡣ㸪ᕷᕝ࡯࠿

㸦1981㸧ࡀ᝿ᐃࡋࡓpaired bend࡟࠾࠸࡚㸪ᕥᶓࡎࢀ᩿ᒙᮾഃࡢᶓࡎࢀᘬᙇሙ࡟࠾ࡅࡿሁ

✚┅ࡢỿ㝆࡜㸪ࡼࡾすഃࡢᶓࡎࢀᅽ⦰ሙ࡟࠾ࡅࡿᪧሁ✚┅୰ᚰࡢୖ᪼ࡢ⧞ࡾ㏉ࡍ࡜࠸࠺ᆅ

ྐࢆ཯ᫎࡋ࡚࠸ࡿྍ⬟ᛶࡀ࠶ࡿ㸬ࡋ࠿ࡋ㸪paired bendࡢⓎ㐩㐣⛬࡟࠾࠸࡚㸪ࡑࢀࡀ㡰ḟ୍

᪉ྥ࡟⛣ືࡋ࡚࠸ࡃࡼ࠺࡞⌧㇟ࡣ୍⯡࡟▱ࡽࢀ࡚࠸࡞࠸㸦Mann, 2007㸧㸬ᶓࡎࢀᘬᙇሙࡢ 㛤ᨺᛶᒅ᭤࡟࠾࠸࡚㸪≀⌮ⓗ࡟⬤ᙅ࡞ᆅẆ㒊ศࡀᏑᅾࡍࡿሙྜ㸪ࡑࡢ㒊ศࡀୖ᪼ሙ࡜࡞ࡿ

ࡇ࡜ࡀ㆟ㄽࡉࢀ࡚࠸ࡿ㸦Dooley et al., 2012㸧㸬ࡇࡢࡼ࠺࡞㒊ศࡀ࿴Ἠሁ✚┅ࡢᆅୗ࡛ᮾ࡟

㡰ḟ⛣ືࡍࡿࡼ࠺࡞⌧㇟ࡀ㉳ࡇࡿ࠿ࡶࡋࢀ࡞࠸㸬࿴Ἠሁ✚┅ࡢⓎ㐩ᶵᵓ࡟ࡘ࠸࡚ࡣࡉࡽ࡟

㆟ㄽࡍࡿᚲせࡀ࠶ࡿࡀ㸪ᮏ◊✲ࡢ♧၀ࡣ㸪࿴Ἠሁ✚┅࡛ࡣ▷ᮇ㛫࡛ỿ㝆ሙ࠿ࡽୖ᪼ሙ࡬࡜

㌿᥮ࡋ࡚࠸ࡓࡇ࡜ࢆ㛫᥋ⓗ࡞ࡀࡽᨭᣢࡍࡿึࡵ࡚ࡢ⇕ᖺ௦Ꮫⓗドᣐ࡜ゝ࠼ࡿ㸬ᶫ∎࡯࠿

㸦1993㸧ࡣ㸪ῐ㊰ᓥࡢ༡㒊┦ࡢሁ✚┦࡜ྂὶྥ࠾ࡼࡧ○ᒌ≀ࡢ≉ᚩ࠿ࡽ㸪༡㒊┦ሁ✚᫬࡟

ࡣࡍ࡛࡟༡㒊┦໭ഃࡀୖ᪼ࡢⴭࡋ࠸๐๤ሙ࡛࠶ࡗࡓ࡜᥎ᐃࡋ࡚࠸ࡿ㸬ࡍ࡞ࢃࡕ㸪ሁ✚┅୰

ᚰࡢ⛣ືᚋࡢᪧሁ✚┅୰ᚰࡢୖ᪼㔞ࡣẚ㍑ⓗ኱ࡁ࡞ࡶࡢ࡜⪃࠼ࡽࢀࡿࡀ㸪ᮏ◊✲ࡢ⇕ᖺ௦ ࡣࡇࡢぢゎࢆᙉࡃᨭᣢࡍࡿ㸬

㸲㸬㸱㸬㸰 ࿴Ἠᒙ⩌ࡢᮾ㐍࡜㡿ᐙ࣭ᒣ㝧ᖏࡢⅆᡂάືࡢ㛵ಀ

࿴Ἠᒙ⩌ࡢᮾ࡬ࡢሁ✚ᖺ௦ࡢⱝ໬㸦࠸ࢃࡺࡿᮾ㐍㸧ࡢ㏿ᗘ࡟㛵ࡋ࡚ࡣ㸪ࡇࢀࡲ࡛࡟໬▼

ᒙᗎ࡜ྂᆅ☢Ẽᒙᗎ࡟ࡼࡿ᳨ウ⤖ᯝࡀ♧ࡉࢀ࡚࠸ࡿ㸬໬▼ᒙᗎ࡜ྂᆅ☢Ẽᒙᗎ࠿ࡽᴫ⟬ࡉ

ࢀࡿ್ࡣࡑࢀࡒࢀ25 km㸭m.y.㸦ᕷཎ࡯࠿, 1986㸧㸪21 km㸭m.y.㸦ᑠ⋢, 1990㸧࡛࠶ࡿ㸬࿴

Ἠᒙ⩌ࡢࢪࣝࢥࣥFTᖺ௦ࡣ㸪๓㏙ࡢᐑ⏣࡯࠿㸦1994㸧࡜ᮏ◊✲࡟ࡼࡿ࿴Ἠᒣ⬦ᆅᇦ㸦71.4 s4.6 Ma㸪70.3s4.8 Ma㸧ࡢ௚࡟㸪ᅄᅜᯇᒣᆅᇦ㸦77.3s4.4 Ma㸸బ⸨࡯࠿, 2005㸧㸪ᅄᅜ

୰ኸ㒊ᆅᇦ㸦76.8s4.8 Ma㸪92.1s11.4 Ma㸸㔝⏣࡯࠿, 2010㸧࡛ ᐃࡉࢀ࡚࠾ࡾ㸪࿴Ἠᒙ

⩌୺ศᕸᇦࡢす➃࠿ࡽᮾ➃ࡢ⠊ᅖࢆ⥙⨶ࡋ࡚࠸ࡿ㸦Fig. 27㸧㸬ᅄᅜᆅᇦࡢ3ヨᩱࡢࢪࣝࢥࣥ

FTᖺ௦ࡣ㸪ࢥࣥࣇ࢓࢖ࣥࢻ࣭ࢺࣛࢵࢡ㛗ゎᯒࡢ⤖ᯝ࡟᭷ព࡞▷⦰ࡣㄆࡵࡽࢀࡎ㸪ሁ✚ᖺ௦

ࢆಖᣢࡋ࡚࠸ࡿ࡜ゎ㔘ࡉࢀ࡚࠸ࡿ㸬ࡋ࠿ࡋ㸪92.1s11.4 Ma࡟ࡘ࠸࡚ࡣ㸪ᅄᅜす㒊࣭୰ኸ㒊 ᆅᇦ࡛ ᐃࡉࢀࡓ௚ࡢ2ࡘࡢFTᖺ௦ࡢ୰ኸ್࡜኱ࡁࡃ␗࡞ࡿࡔࡅ࡛࡞ࡃ㸪㏆᥋ᆅⅬࡢᨺᩓ

⹸໬▼࡛ࡣ୰ᮇ࢝ࣥࣃࢽ࢔ࣥᮇ㸦⣙80.5㹼76.5 Ma㸸Ogg and Hinnov, 2012㸧ࡀ♧၀ࡉࢀ

࡚࠸ࡿ㸦㔝⏣࡯࠿, 2010㸧㸬ࡇࡢᖺ௦ࡣ ᐃࡀᅔ㞴࡞ᚤ⣽࡞ࢪࣝࢥࣥ⢏Ꮚࢆ౑⏝ࡋ࡚࠾ࡾ㸪

⥲ࢺࣛࢵࢡᩘࡀᑡ࡞࠸ࡓࡵ㸪ᮏ◊✲࡛ࡢ᳨ウ࡟᥇⏝ࡋ࡞࠸㸬ᐑ⏣࡯࠿㸦1994㸧࡟ࡼࡿ FT ᖺ௦ࡢ࠺ࡕ㸪๓㏙ࡢ 3 ヨᩱࡣி㒔ࣇ࢕ࢵࢩ࣭ࣙࣥࢺࣛࢵࢡ࡛ ᐃࡉࢀࡓࢹ࣮ࢱ࡛࠶ࡿࡀ㸪  ᐃ⪅㸸ྠ♫᷄ཎ ᚭẶ㸪⇕୰ᛶᏊ↷ᑕ㸸❧ᩍ኱Ꮫᐇ㦂ཎᏊ⅔㸪 ᐃ᪉ἲ㸸ED2㸦⤖ᬗእ 㒊㠃㸧࡛࠶ࡾ㸪ࡑࢀ௨እࡢFTᖺ௦࡛ࡣ㸪 ᐃ⪅㸸ྠ♫ᒾ㔝ⱥᶞẶ㸪⇕୰ᛶᏊ↷ᑕ㸸᪥ᮏཎ Ꮚຊ◊✲㛤ⓎᶵᵓJRR㸱ྕ⅔㸪 ᐃ᪉ἲ㸸ED1㸦⤖ᬗෆ㒊㠃㸧࡜᮲௳ࡀ኱ࡁࡃ␗࡞ࡿࡓࡵ㸪 ᮏ◊✲࡛ࡢᮾ㐍㏿ᗘࡢィ⟬࡟ࡣ౑⏝ࡋ࡞࠸㸬࿴Ἠᒙ⩌ࡢࢪࣝࢥࣥFTᖺ௦ࡣ㸪MTLἢ࠸ࡢ ᮾす᪉ྥࢆᶓ㍈࡜ࡋ࡚㓄ิࡍࡿ࡜㸪๓㏙ࡢᅄᅜ୰ኸ㒊ᆅᇦࡢ1ヨᩱ㸦㔝⏣࡯࠿, 2010㸧࡜࿴

Ἠᒣ⬦す➃㒊ࡢ1ヨᩱ㸦ᐑ⏣࡯࠿, 1994㸧ࢆ㝖ࡁ㸪࡯ࡰ┤⥺㛵ಀ࡛ᮾ࡯࡝ⱝࡃ࡞ࡿ㸦Fig. 27㸧㸬 ࡑࡢ໙㓄ࢆబ⸨࡯࠿㸦2005㸧㸪㔝⏣࡯࠿㸦2010㸧ࡢྛ1ヨᩱ࡜ᮏ◊✲ࡢ 2ヨᩱࡢィ4ヨᩱ

ࡢ⥺ᙧᅇᖐ࡛ィ⟬ࡍࡿࡇ࡜࡛㸪ᯇᒣᆅᇦ࠿ࡽ࿴Ἠᒣ⬦ᆅᇦ㛫ࡢ࿴Ἠᒙ⩌ࡢᖹᆒᮾ㐍㏿ᗘ 34.6s4.3 (1Ȫ) km㸭m.y. ࡀぢ✚ࡶࡽࢀࡿ㸬㔝⏣࡯࠿㸦2010㸧ࢆ㝖ࡁ㸪࠸ࡎࢀࡶ࿴Ἠᒙ⩌

໭⦕ࡢᇶᗏ୙ᩚྜ௜㏆ࡢヨᩱ࡛࠶ࡿࡓࡵ㸪ࡇࡢ್ࡣ࿴Ἠᒙ⩌ሁ✚㛤ጞ᫬ᮇࡢᮾ㐍㏿ᗘࢆ♧

ࡍ㸬୍᪉㸪ྂᆅ☢Ẽᒙᗎ࠾ࡼࡧ໬▼ᒙᗎ࡟ࡼࡿࡇࢀࡲ࡛ࡢ᥎ㄽࡣ㸪ሁ✚┅୰ᚰࡢ⛣ື㏿ᗘ

ࢆ♧ࡋ࡚࠸ࡿ࡜ゝ࠼ࡿ㸬FTᖺ௦࡟ࡼࡿ᳨ウ⤖ᯝ࡜ࡇࢀࡽࡀ␗࡞ࡿཎᅉ࡜ࡋ࡚㸪ྂᆅ☢Ẽᒙ ᗎ࠾ࡼࡧ໬▼ᒙᗎࡢศゎ⬟ࡢၥ㢟࡛㸪ᐇ㝿ࡼࡾሁ✚ᮇ㛫ࡀ኱ࡁࡃぢ✚ࡶࡽࢀࡓྍ⬟ᛶࡸ㸪 FTᖺ௦ࡢㄗᕪࡢᙳ㡪➼ࡀ⪃࠼ࡽࢀࡿ㸬ᮏ◊✲࡛ぢ✚ࡶࡽࢀࡓᮾ㐍㏿ᗘ࠿ࡽ༢⣧ィ⟬࡛᥎ᐃ ࡉࢀࡿ࿴Ἠᒙ⩌ࡢሁ✚ᮇ㛫ࡣ㸪ᅄᅜᯇᒣᆅᇦ࠿ࡽ࿴Ἠᒣ⬦ࡲ࡛⣙77.9㹼70.3 Ma࡛࠶ࡿ㸬

࿴Ἠᒙ⩌ࡢす᪉ᘏ㛗㸦ᒣ໭࣭኱⸨, 2000 ࡞࡝㸧࡜ࡉࢀࡿ኱㔝ᕝᒙ⩌ࡣ㸪࢖ࣀࢭ࣒ࣛࢫ໬

▼ᒙᗎࡼࡾInoceramus hobetsensis_ᖏ࠿ࡽInoceramus amakusensis_{ᖏ࡟༊ศࡉࢀ࡚࠸ࡿ}

㸦㔝⏣, 1994㸧㸬Hayakawa and Hirano㸦2013㸧ࡢ⼎ዀᒙ⩌࡟࠾ࡅࡿ࢖ࣀࢭ࣒ࣛࢫ໬▼ᖏ

࡛᫬௦ᑐẚࡍࡿ࡜㸪኱㔝ᕝᒙ⩌ࡢ໬▼ᖺ௦ࡣ㸪᭱㛗࡛୰ᮇࢳ࣮ࣗࣟࢽ࢔ࣥᮇ࠿ࡽ๓ᮇ࢝ࣥ

ࣃࢽ࢔ࣥᮇ๓ᮇࡢ࠾࠾ࡼࡑ93㹼82 Ma㸦Ogg and Hinnov, 2012㸧࡜⪃࠼ࡽࢀࡿ㸬ࡇࢀࡼࡾ

኱㔝ᕝᒙ⩌ࡢሁ✚ᖺ௦ࡣ㸪ᅄᅜᆅᇦࡢ࿴Ἠᒙ⩌ࡼࡾⱝᖸྂ࠸ࡇ࡜ࡀ♧၀ࡉࢀࡿ㸦Fig. 27㸧㸬 ࡍ࡞ࢃࡕ㸪኱㔝ᕝᒙ⩌࡜࿴Ἠᒙ⩌ࡢሁ✚ᮇ㛫ࡣ㔜」ࡋ࡚࠾ࡽࡎ㸪ሁ✚┅୰ᚰࡢᮾ㐍ࡀ஑ᕞ

0 500 Izumi Group

Onogawa G.

0 200 400 600 800 1000

80 100

60 120 140

Age (Ma)

K y u s h u S h i k o k u K i n k i C h u b u

Distance along MTL (km)

WestЋ ЍEast

modified after Yuhara et al. (2000)

from Matsuyama

10 km /m.y.

20 km /m.y.

40 km /m.y.

San’yo and northern

Kyushu granitoids Ryoke granitoids

Onogawa Group

Sennan Rhyolites Izumi Group

Rb–Sr whole-rock isochron ages Zircon fission track ages

Biostratigraphy (Yuhara et al., 2000)

(Sato et al., 2005; Noda et al., 2010 in Shikoku and Miyata et al., 1993; this study in the Izumi Mountains)

(Noda, 1994; revised on the

basis of Hayakawa and Hirano, 2013)

Maastr.

PaleogeneLower CretaceousCampanian

Sant.

Con.

Tur.

Cen.

Fig. 27. Whisker plots showing Rb–Sr isochron ages of granitoids, fission-track ages, and biostratigraphic ages of sedimentary rocks distributed along the MTL, southwestern Japan. Rb–Sr whole-rock isochron ages of the Ryoke and San’ yo granitoids (gray squares and open squares, respectively) are from Yuhara et al.

(2000). Zircon fission-track ages of the Sennan Rhyolites (black solid rhombus) are from this study. Zircon fission-track ages of the Izumi Group are from Miyata et al.

(1994), Sato et al. (2005), Noda et al. (2010) (grey solid circles), and this study (black

solid circles). Error bars indicate two standard errors (2σ). The biostratigraphic age

of the Onogawa Group (Noda, 1994) was revised following Hayakawa and Hirano

(2013). The thin dashed line represents the younger limit of whole-rock ages

(Yuhara et al., 2000). The thick line represents the approximate formation age of

the formation of the basin in which the Izumi Group was deposited.

ᆅ᪉࠿ࡽ㏆␥ᆅ᪉ࡲ࡛㐃⥆ࡋ࡚⏕ࡌࡓྍ⬟ᛶࡣྰᐃࡉࢀ࡞࠸㸬

MTLࡢ໭ഃ࡟ศᕸࡍࡿⰼᓵᒾ㢮ࡢᨺᑕᖺ௦ࢆࡶ࡜࡟ࡋࡓⓑள⣖ⅆᡂάືࡢᮾ㐍㏿ᗘࡀ࠸

ࡃࡘ࠿ぢ✚ࡶࡽࢀ࡚࠸ࡿ㸦౛࠼ࡤ㸪⣙30 km㸭m.y.㸸Kinoshita, 1995㸧㸬Yuhara et al.㸦2000㸧

࡟ࡼࡾࡲ࡜ࡵࡽࢀࡓ㡿ᐙⰼᓵᒾ㢮࣭ᒣ㝧ⰼᓵᒾ㢮ࡢRb–Sr඲ᒾ࢔࢖ࢯࢡࣟࣥᖺ௦࡜࿴Ἠᒙ

⩌ࡢሁ✚ᖺ௦ࢆMTLἢ࠸ࡢ఩⨨࡛ẚ㍑ࡍࡿ࡜㸪Rb–Sr඲ᒾ࢔࢖ࢯࢡࣟࣥᖺ௦ୗ㝈ࡢᮾ࡬ࡢ ⱝ໬ࢆ♧ࡍⅬ⥺㸦37 km㸭m.y.㸧࡜㸪ᮏ◊✲࡟ࡼࡿ࿴Ἠሁ✚┅ᮾ㐍ࡢᅇᖐ┤⥺㸦35 km㸭 m.y.㸧ࡣ㸪4.5㹼5 m.y.ࡢ᫬㛫㛫㝸ࢆ௓ࡋ࡚ᴫࡡࣃࣛࣞࣝ࡞㛵ಀ࡟࠶ࡿ㸦Fig. 27㸧㸬4.5㹼5 m.y.

ࡣᮾす㊥㞳࡛⣙170 km࡟┦ᙜࡍࡿࡓࡵ㸪ᚋᮇⓑள⣖ࡢす༡᪥ᮏ࡟࠾࠸࡚㸪῝ᡂⅆᡂάືࡢ άⓎ࡞ᆅᇦ࡜࿴Ἠᒙ⩌ࡢሁ✚┅ᮾ➃ࡣ 170 km ࡯࡝ࡢ㊥㞳ࢆಖࡕࡘࡘඹ࡟ᮾ࡬⛣ືࡋ࡚࠸

ࡓࡇ࡜࡟࡞ࡿ㸬

㸲㸬㸱㸬㸱 ࿘㎶ᆅᇦࡢⰼᓵᒾ㢮ࡢ෭༷ྐ࡜ࡢẚ㍑

ᑼ࢔ࢲ࣓ࣟᒾ࣭Ἠ༡ὶ⣠ᒾ㢮ࢆ༊ศࡍࡿࣈࣟࢵࢡB࡜ࣈࣟࢵࢡCࡢ㛵ಀ࡜㢮ఝࡍࡿࡢ ࡀ㸪᫂▼ᾏᓙࢆᣳࢇ࡛ศᕸࡍࡿῐ㊰ᓥ໭㒊ࡢ㡿ᐙⰼᓵᒾ㢮ⰼᓵᒾ㉁ᒾ࡜භ⏥ᒣᆅࡢᒣ㝧ⰼ ᓵᒾ㢮භ⏥ⰼᓵᒾࡢ෭༷ྐ࡛࠶ࡿ㸦Fig. 21B㸧㸬ῐ㊰ᓥ໭㒊ࡢⰼᓵᒾ㉁ᒾࡢ࢔ࣃࢱ࢖ࢺ FT ᖺ௦ࡣ83s18 Ma㸦Ito, 2004㸧࡛࠶ࡾ㸪Ἠ༡ὶ⣠ᒾ㢮㸦ࣈࣟࢵࢡB㸧࠿ࡽᚓࡽࢀࡓ࢔ࣃࢱ

࢖ࢺFTᖺ௦࡜ࡼࡃ୍⮴ࡍࡿ㸬 ୍᪉㸪࣮ࣞࢨ࣮࢔ࣈ࣮ࣞࢩࣙࣥㄏᑟ⤖ྜࣉࣛࢬ࣐㉁㔞ศᯒ ἲࢆ⏝࠸ࡓࢪࣝࢥࣥ࡜࢔ࣃࢱ࢖ࢺ FT ᖺ௦࠿ࡽ᥎ᐃࡉࢀࡓභ⏥ⰼᓵᒾࡢ෭༷ྐ㸦ᮎᒸ࡯࠿,

2010㸧ࡣ㸪ࢪࣝࢥࣥFTᖺ௦ࡢ㛢㙐 ᗘࢆ㏻㐣ࡍࡿࡢࡀ68.6㹼39.0 Ma㸪࢔ࣃࢱ࢖ࢺFTᖺ

௦ࡢ㛢㙐 ᗘࢆ㏻㐣ࡍࡿࡢࡀ30.8㹼19.5 Ma࡛࠶ࡿ㸬ࡍ࡞ࢃࡕ㸪ᑼ࢔ࢲ࣓ࣟᒾ㸦ࣈࣟࢵ

ࢡC㸧ࡢ300Υ௨ୗࡢ෭༷ྐࡣ㸪ῐ㊰ᓥ໭㒊ࡢⰼᓵᒾ㉁ᒾࡼࡾࡶභ⏥ⰼᓵᒾ࡟㢮ఝࡍࡿ㸦Fig.

21A, B㸧㸬ῐ㊰ᓥ໭㒊ࡢ㡿ᐙⰼᓵᒾ㢮ࡣ㸪࿴Ἠᒣ⬦ᆅᇦࡢࣈࣟࢵࢡB࡜ྠᵝ࡟㸪࿴Ἠᒙ⩌ሁ

✚௨๓࡟ୖ᪼ᚋ㸪኱ࡁ࡞ ᗘኚ໬ࢆక࠺ỿ㝆࣭ୖ᪼ࢆ⤒㦂ࡋ࡚࠸࡞࠸ࡢ࡛࠶ࢁ࠺㸬

㸲㸬㸲 ⤖ ㄽ

࿴Ἠᒣ⬦ᆅᇦࡢ࿴Ἠᒙ⩌㸪Ἠ༡ὶ⣠ᒾ㢮㸪࠾ࡼࡧᑼ࢔ࢲ࣓ࣟᒾࡢ⇕ᖺ௦Ꮫⓗࢹ࣮ࢱࡼ

ࡾ㸪ᮏᆅᇦࢆࣈࣟࢵࢡA㸪B㸪C࡟୕ศࡍࡿࡇ࡜࡛㸪ࡑࡢ෭༷ྐࢆྜ⌮ⓗ࡟ゎ㔘࡛ࡁࡿࡇ࡜

ࡀ᫂ࡽ࠿࡜࡞ࡗࡓ㸬࿴Ἠሁ✚┅໭⦕࡛ࡢ୙㐃⥆࡞᩿ᒙ⩌ࢆక࠺࿴Ἠሁ✚┅ࡢⓎ㐩࡛ࡣ㸪ࣈ

ࣟࢵࢡB ࡢᇶ┙ᒾࡀ࿴Ἠᒙ⩌㸦ࣈࣟࢵࢡA㸧ࡢỿ㝆࣭ୖ᪼ࡢᙳ㡪ࢆཷࡅ࡞࠸ࡓࡵ㸪୧ࣈࣟ

ࢵࢡࡢ෭༷ྐࡣ኱ࡁࡃ␗࡞ࡿ㸬࿴Ἠሁ✚┅ỿ㝆᫬࡟Ⓨ㐩ࡋࡓ࡜ぢࡽࢀࡿ㞜⾜≧ࡢ୙㐃⥆࡞

᩿ᒙ⩌ࡣ㸪࿴Ἠሁ✚┅ࡀᶓࡎࢀᘬᙇሙ࡛ᙧᡂࡉࢀࡓྍ⬟ᛶࢆ♧၀ࡍࡿ㸬Ἠ༡ὶ⣠ᒾ㢮㸦ࣈ

ࣟࢵࢡB㸧࡟㈏ධࡋࡓᑼ࢔ࢲ࣓ࣟᒾ࡟ࡘ࠸࡚ࡣ㸪⇕ᙳ㡪ࡣᮾ㒊ᆅᇦ࡟㝈ᐃࡉࢀ㸪⌧ᅾศᕸ ࡍࡿᑼ࢔ࢲ࣓ࣟᒾࡢᗈ⠊ᅖ㸦ࣈࣟࢵࢡC㸧ࡀ㸪ⓑள⣖௨㝆࡟Ἠ༡ὶ⣠ᒾ㢮࡜᥋ࡋࡓࡇ࡜ࡀ

♧၀ࡉࢀࡓ㸬ࣈࣟࢵࢡB ࡢἨ༡ὶ⣠ᒾ㢮࣭ᑼ࢔ࢲ࣓ࣟᒾࢆ༡໭࠿ࡽᣳࡴቃ⏺᩿ᒙ࣭᩿ᒙ

⩌ࡀ㏫᩿ᒙ࡜ࡋ࡚άືࡍࡿࡇ࡜࡛㸪࿴Ἠᒙ⩌ࢆྵࡴࣈࣟࢵࢡ A ࡜ᑼ࢔ࢲ࣓ࣟᒾࡢᗈ⠊ᅖ

ࢆྵࡴࣈࣟࢵࢡ C ࡢୖ᪼ࡀ㉳ࡗࡓ࡜⪃࠼ࡽࢀࡿ㸬ࡉࡽ࡟㸪ࡇࢀࡽࡢ⇕ᖺ௦Ꮫⓗ࡞᳨ウ࠿ࡽ

ࡣ㸪࿴Ἠᒙ⩌ࡢ໭⦕㒊࿘㎶࡟࠾࠸࡚࿴Ἠᒙ⩌ሁ✚ᚋ࡟㈏ධࡋࡓ኱つᶍ࡞ᒾయࡢᏑᅾࡣᨭᣢ ࡉࢀ࡞࠿ࡗࡓ㸬ࡲࡓ㸪࿴Ἠᒣ⬦ᮾ㒊ᆅᇦ࡟࠾ࡅࡿ࿴Ἠᒙ⩌࠾ࡼࡧᑼ࢔ࢲ࣓ࣟᒾࡢ⇕ᖺ௦ Ꮫⓗ᳨ウ࠿ࡽ㸪࿴Ἠᒙ⩌ࡢᇙἐ࠿ࡽୖ᪼࡬ࡢኚ㑄ࡣᩘ Ma ࡢ▷ᮇ㛫࡛⏕ࡌࡓࡇ࡜ࡀ♧၀ࡉ

ࢀࡓ㸬ࡇࢀࡣ㸪ሁ✚┅୰ᚰࡢᮾ࡬ࡢ⛣ື࡜ᪧሁ✚┅୰ᚰࡢୖ᪼ࢆ⧞ࡾ㏉ࡍ㸦ᕷᕝ࡯࠿, 1981㸧

ࡼ࠺࡞㸪࿴Ἠሁ✚┅ࡢᮾ㐍㐣⛬ࢆ཯ᫎࡋࡓࡶࡢ࡜⪃࠼ࡽࢀࡿ㸬

㸳㸬⿕⇕ࣔࢹࣜࣥࢢ

㸳㸬㸯 ⇕ᖺ௦࡜ࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࢆ⏝࠸ࡓ ᗘᒚṔࡢ᥎ᐃ

࿴Ἠᒣ⬦ᮾ㒊ᆅᇦࡢᇙἐ⿕⇕ྐࢆ᚟ඖࡍࡿࡓࡵ㸪୍ᐃ᮲௳ࢆ‶ࡓࡍ ᗘࣃࢫࢆ⮬ື᳨⣴

ࡍࡿࣉࣟࢢ࣒ࣛࢆసᡂࡋࡓ㸬࿴Ἠᒙ⩌࡜ࡢ୙ᩚྜ㏆ഐ࡟఩⨨ࡍࡿNg08ࡢᨺᑕᖺ௦࡜㛢㙐  ᗘ㸪ᮾ㐍㏿ᗘࡲࡓࡣ໬▼ᖺ௦࠿ࡽ᥎ᐃࡉࢀࡿሁ✚ᖺ௦㸪࿴Ἠᒣ⬦ᮾ⦕㒊࡛ᚓࡽࢀࡓ Rm㸻 2.64%ࡢ㸱᮲௳ࢆᣊ᮰᮲௳࡜ࡋࡓ㸬

 ᗘᒚṔ࠿ࡽࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࡢィ⟬࡟ࡣSIMPLE–Ro㸦Suzuki et al., 1993㸧ࡢ࠺ࡕ㸪 EASY%Ro㸦Burnham and Sweeney, 1991㸧࡟ࡼࡾ㍑ṇࡉࢀࡓࢫ࣮࣒࢟㸦B㸧ࢆ㐺⏝ࡋࡓ㸬

ࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࡢ⿕⇕ ᗘ࣭᫬㛫࡟ࡼࡿኚ໬࡟ࡘ࠸࡚ࡣ㸪௨ୗࡢᘧ࡛ᐃ⩏ࡍࡿࡇ࡜ࡀ

࡛ࡁࡿ㸦Suzuki et al., 1993㸧㸬

>

^{ln 3.7}

@

^(1.1)

exp Roo Fc _ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ

Ro

) 2 . 1 ( exp 0 ¸¹·ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ ࠉࠉ

¨©§ ^fa

³

^{k dt}

fa

F_c ^t

^{( )}

^(1.3)

exp ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ ࠉ E RT t

A

k _app

) 4 . 1 ( ln ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ ࠉ E

D Ro E_app

฿㐩ࡍࡿࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࡀRo_࡛࠶ࡿ㸬Rooࡣ⿕⇕ࢆཷࡅ࡚࠸࡞࠸ึ⏕ⓗ࡞͆ࣅࢺࣜࢼ

࢖ࢺ͇ࡢ཯ᑕ⋡࡛࠶ࡾ㸪㏻ᖖRoo_㸻0.2ࡀ୚࠼ࡽࢀࡿ㸬Fcࡣࣅࢺࣜࢼ࢖ࢺࡀཷࡅࡓ⇕ᙳ㡪ࡢ

✚⟬࡛㸪᭷ᶵ≀ࡢ⿕⇕࡟ࡼࡿ㔜㔞ῶᑡ㔞࡜㛵㐃ࡍࡿ್࡛࠶ࡿ㸬fa ࡣࣅࢺࣜࢼ࢖ࢺࡢ⇕ศゎ

࡜㔜㔞ẚ࡟㛵ࡍࡿಀᩘ࡛0.85ࡀ୚࠼ࡽࢀࡿ㸬kࡣ཯ᛂ㏿ᗘᐃᩘ࡜࿧ࡤࢀ㸪ࣅࢺࣜࢼ࢖ࢺࡢ ᚤᑠ᫬㛫࡛ࡢ㔜㔞ኚ໬㔞ࡢඖ㔜㔞࡟ᑐࡍࡿẚ౛ᐃᩘ࡛࠶ࡾ㸪 ᗘ࡜άᛶ໬࢚ࢿࣝࢠ࣮࡟౫ Ꮡࡍࡿ㸬ࣅࢺࣜࢼ࢖ࢺࡢⅣ໬㐣⛬ࡣArrhenius๎࡟ᚑ࠺࡜ࡉࢀࡿ㸦Burnham and Sweeney,

1991㸧㸬k_{ࡢ᫬㛫✚ศ࡟}faࢆ✚⟬ࡋࡓ್ࡀ㸪ࣅࢺࣜࢼ࢖ࢺࡢ⇕ศゎ࡟ࡼࡿ⥲㔜㔞ኚ໬ẚ࡛࠶

ࡿ㸬 ᗘᒚṔࡀT (t )࡛࠶ࡾK༢఩࡛⏝࠸ࡽࢀࡿ㸬Eappࡣࣅࢺࣜࢼ࢖ࢺࡢάᛶ໬࢚ࢿࣝࢠ࣮

࡛࠶ࡾ㸪ࡇࡢ್ࡀ⮬㌟ࡢ཯ᑕ⋡࡟ࡼࡾ㝶᫬ኚ໬ࡋ㸪཯ᑕ⋡ࡀୖ᪼ࡍࡿ࡯࡝ୖ᪼ࡍࡿ㸬ࡍ࡞

ࢃࡕ㸪཯ᑕ⋡ࡀୖ᪼ࡍࡿ࡯࡝ࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࡀୖ᪼ࡋ࡟ࡃࡃ࡞ࡿࡇ࡜ࢆព࿡ࡍࡿ㸬ࡇ ࡢ஦㇟ࡀ㸪㛗ᮇ㛫ࡢᐃ ⿕⇕࡟㛵ࡋ࡚㸪⿕⇕᫬㛫ࡢ㐪࠸࡛ࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࡢኚ໬ࡀ࡯

࡜ࢇ࡝⏕ࡌ࡞࠸࡜࠸࠺㸪࠸ࢃࡺࡿ ᗘ㣬࿴≧ែࢆᘬࡁ㉳ࡇࡍ㸬tࡣ᫬㛫࡛࠶ࡾ㸪⛊༢఩࡛ᢅ

ࢃࢀࡿ㸬A_{ࡣ㢖ᗘᅉᏊ࡛}10¹³ 㸦s^-1㸧㸪R_{ࡣẼయᖖᩘࡢ}8.314 㸦J࣭K^-1mol^-1㸧㸪ɲ࡜ɴࡣ཯ᑕ

⋡ࡢ⮬↛ᑐᩘ࡜άᛶ໬࢚ࢿࣝࢠ࣮࡜ࡢ㛵ಀࡢ⥺ᙧ㏆ఝᘧࡢಀᩘ࡛㸪ᮏ◊✲࡛ࡣSuzuki et al.

㸦1993㸧࡟࠾ࡅࡿࢫ࣮࣒࢟㸦B㸧ࡢɲ㸻9.7㸪ɴ㸻54.1ࢆ౑⏝ࡍࡿ㸬

ᩘ್ࢩ࣑࣮ࣗࣞࢩ࡛ࣙࣥࡣ㸪Fc࡟ࡘ࠸࡚᫬㛫Ǽt࡛㞳ᩓ໬ࡋࡓ௨ୗࡢᘧࢆ⏝࠸ࡿ㸬

^(1.5)

exp

1

ࠉ ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ

¸¹

¨ ·

©

§ ˜'

˜

¦

ⁿ

i

c fa fa ki t

F

^{( )}

^(1.6)

exp ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ ࠉ E RT ti

A

ki _i

Ei࠾ࡼࡧT(ti)ࡣ᫬้ti࡟࠾ࡅࡿࣅࢺࣜࢼ࢖ࢺࡢάᛶ໬࢚ࢿࣝࢠ࣮࠾ࡼࡧ ᗘ࡛࠶ࡿࡀ㸪Ei

ࡣࡑࡢ್⮬య࡟⌧ᅾࡢ཯ᑕ⋡ࡀࣇ࢕࣮ࢻࣂࢵࢡࡍࡿࡓࡵ㸪 ᗘኚ໬ࡢ኱ࡁ࠸ ᗘࣃࢫ࡟࠾

ࡅࡿ㞳ᩓ໬࡟㛵ࡋ࡚ࡣ༑ศ࡟ᑠࡉ࠸᫬㛫ᖜ࡛ศ๭ࡍࡿࡇ࡜ࡀᚲせ࡛࠶ࡿ㸬ᮏ◊✲࡛ࡣ㸪  ᗘ̿᫬㛫ࣃࢫ࠿ࡽࡢࣅࢺࣜࢼ࢖ࢺ཯ᑕ⋡ࡢィ⟬࡟ࡍ࡭࡚ࡇࡢࢫ࣮࣒࢟ࢆ⏝࠸ࡿ㸦Figs. 23, 28࡞࡝㸧㸬

୧➃ࢆᣊ᮰ࡉࢀࡓ ᗘࣃࢫ࠿ࡽ㸪཯ᑕ⋡ࡀRo(ҸRm㸸➨2❶ࢆཧ↷)㸻2.64%ࢆ‶ࡓࡍ  ᗘࣃࢫࢆ᳨⣴ࡍࡿࡓࡵ㸪2㏻ࡾࡢึᮇ᮲௳ࢆ୚࠼ࡓ㸦Fig. 28A, B㸧㸬➨㸯ࡢ᮲௳㸦Fig. 28A㸧 ࡣ㸪ᮏ◊✲࡟ࡼࡿᮾ㐍㏿ᗘࡢぢ✚ࡶࡾ35 km/m.y.࠿ࡽィ⟬ࡉࢀࡿNg08, TK08௜㏆ࡢሁ✚

ᖺ௦㸦⣙70.3 Ma㸧࡜㸪Ng08ࡢ⇕ᖺ௦㸦65.8 Ma㸹㛢㙐 ᗘ173Υ㸧ࢆࡶ࡜࡟ࡋࡓ㸬➨㸰 ࡢ᮲௳㸦Fig. 28B㸧ࡣ㸪࣐࣮ࢫࢺࣜࣄࢳ࢔ࣥᮇࡢୗ㝈ࡢᖺ௦㸦72.1 Ma㸧ࢆሁ✚ᖺ௦࡜ࡋ࡚㸪 Ng08ࡢ2Ȫࡢ⠊ᅖ࡛᭱ࡶⱝ࠸ᖺ௦㸦63.0 Ma㸹㛢㙐 ᗘ173Υ㸧ࢆ⇕ᖺ௦࡜ࡋࡓ㸬ࡍ࡞ࢃ

ࡕ㸪➨㸰ࡢ᮲௳ࡣ⪃៖ࡉࢀ࠺ࡿᮾ㒊࡛ࡢ⿕⇕ࡢ᭱㛗ᮇ㛫ࡢ᮲௳࡛࠶ࡿ㸬࡞࠾㸪࿴Ἠᒣ⬦ᆅ ᇦ୰㒊ࡢᑼ࢔ࢲ࣓ࣟᒾࡢ࢔ࣃࢱ࢖ࢺFTᖺ௦50.0 Maࢆࡶ࡜࡟㛢㙐 ᗘ100Υࡢ ᗘࣃࢫ

ࢆ౽ᐅୖ୚࠼࡚࠶ࡿࡀ㸪173㹼100Υࡢ༊㛫࡛ࡢ཯ᑕ⋡ࡢኚ໬ࡣ 0.01㸣Ro ᮍ‶࡛࠶ࡾ㸪⤖

ᯝⓗ࡟ ᗘࣃࢫࡢỴᐃ࡟ᐤ୚ࡋ࡚࠸࡞࠸㸬 50 Ma௨㝆ࡢ 100Υ௨ୗ࡛ࡢ⿕⇕࡟ࡘ࠸࡚ࡶ㸪

ྠᵝ࡛࠶ࡿ࡜⪃࠼ࡽࢀࡿ㸬ሁ✚ᚋ࠿ࡽ᭱㧗ྂᆅ ࢆ⤒㦂ࡋ࡚㸪173Υࡲ࡛෭༷ࡍࡿ㛫ࡢ ᗘ

ࣃࢫ࡟ࡘ࠸࡚㸪2 ࡘࡢࣃࢱ࣮ࣥࢆ᳨ウࡋࡓ㸬୍ࡘࡣ㸪᭱㧗ྂᆅ ࡟฿㐩ࡋࡓᚋ㸪㏿ࡸ࠿࡟

173Υࡲ࡛෭༷ࡍࡿሙྜ࡛㸪ࡇࡢ༊㛫ࡢ ᗘࣃࢫࡢྍኚࢥࣥࢺ࣮࣏ࣟࣝ࢖ࣥࢺࡣ㸯Ⅼ࡛࠶ࡿ

㸦Fig. 28ࡢ㉥Ⰽ⥺㸧㸬ࡓࡔࡋ㸪ィ⟬ୖᚲせ࡞᭱㧗ྂᆅ ࡛ࡢ⿕⇕᫬㛫ࢆ0.01 m.y.࡜ࡋ࡚୚

࠼࡚࠸ࡿ㸬ࡶ࠺୍ࡘࡣ㸪᭱㧗ྂᆅ ࡟฿㐩ࡋࡓᚋ㸪ᐃ ≧ែ࡛᭱኱ᮇ㛫ࡢ⿕⇕ᚋ㸪㏿ࡸ࠿

࡟෭༷ࡍࡿሙྜ࡛࠶ࡿ㸬ࡇࡢ༊㛫ࡢ ᗘࣃࢫࡢྍኚࢥࣥࢺ࣮࣏ࣟࣝ࢖ࣥࢺࡣ2Ⅼ࡛࠶ࡿ㸦Fig.

28ࡢ㟷Ⰽ⥺㸧㸬 ᗘࡢኚ໬⋡࡟ࡘ࠸࡚ࡣ㸪᪼ ࣭㝆 ࡜ࡶ150Υ㸭m.y.ࢆୖ㝈࡜ࡋࡓ㸬᳨⣴

ࡢ୍⮴⢭ᗘࡣ⿕⇕ ᗘs0.25Υࡲࡓࡣs0.005㸣Rm ࢆタᐃࡋ㸪ࣃࢫࡣ᭱㧗ྂᆅ ࡟฿㐩ࡍ

ࡿ᫬㛫ࢆ0.1 m.y.㛫㝸࡛ኚ᭦ࡋ࡚ᥥ⏬ࡋࡓ㸬ゎᯒࡢ⤖ᯝ㸪➨㸯ࡢ᮲௳㸦70.3–65.8 Ma㸧࡛

ࡣ㸪68.9–66.2 Maᮇ㛫࡟᭱㧗ྂᆅ  228㹼249Υ࡛ࡢ⿕⇕ࡀ᚟ඖࡉࢀࡓ㸬㏿ࡸ࠿࡟෭༷ࡍ

ࡿሙྜࡢᖹᆒⓗ࡞᪼ ࣭㝆 ⋡ࡣ65Υ㸭m.y.࡛࠶ࡗࡓ㸬⿕⇕ᙜ᫬ࡢᆅ ໙㓄࡜ࡋ࡚30Υ㸭 km㸪 ᗘኚ໬ࡢཎᅉࡀᇙἐ࣭ୖ᪼࡟ࡼࡿ࡜௬ᐃࡍࡿ࡜㸪ᚋ㏙ࡢᇙἐຠᯝࢆ↓どࡋࡓሙྜ㸪

㻔㻹㼍㻕 㻣㻜 㻢㻜 㻡㻜 㻠㻜 㻣㻜 㻢㻜 㻡㻜 㻠㻜

50Υ 100Υ 150Υ 200Υ 250Υ 300Υ

Ro=2.64 Ro=2.64

A. 70.4-65.8 B. 72.1-63.0

Fig. 28. Time-temperature path models of the Izumi Group with vitrinite reflectance and thermal chlonological data in the Izumi Montains.

Vitrinite reflectance was calculated using scheme (B) of Suzuki et al.

(1993). For this study, two assumption were made for modelling: (A)

Depositional time=70.4 Ma, time of cooling at 173Υ =65.8 Ma; (B)

Depositional time=72.1 Ma, time of cooling at 173Υ=63.0 Ma.

2.64%Ro ApFT

Kfd K-Ar

ISB

ISB

ZrnFT

Fig. 29. Thermal histories of the East Asia continental margin (Cretaceous Gyeongsang, Jinan, and Izumi basins, Yanji granitoids, Ryoke, Sambagawa, and Shimanto belts) in the Late Cretaceous to present. Thermal history of the Izumi basin was estimated in this study. Others are after Choi and Lee (2009).

modified from Choi and Lee (2009)

ᖹᆒࡋ࡚2.2 km㸭m.y.ࡢᇙ✚㏿ᗘ࡜๐๤㏿ᗘࡀィ⟬ࡉࢀࡿ㸬➨㸰ࡢ᮲௳㸦72.1–63.0 Ma㸧

࡛ࡣ㸪70.8–63.3 Ma ᮇ㛫࡟᭱㧗ྂᆅ  220㹼244Υ࡛ࡢ⿕⇕ࡀ᚟ඖࡉࢀࡓ㸬㏿ࡸ࠿࡟෭༷

ࡍࡿሙྜࡢᖹᆒⓗ࡞᪼ ࣭㝆 ⋡ࡣ 30Υ㸭m.y.࡛࠶ࡗࡓ㸬๓⪅࡜ྠᵝ࡟௬ᐃࡍࡿ࡜㸪ᖹᆒ

ࡋ࡚1.0 km㸭m.y.ࡢᇙ✚㏿ᗘ࡜๐๤㏿ᗘࡀィ⟬ࡉࢀࡿ㸬

ࡇࡢ࿴Ἠሁ✚┅ࡢ ᗘ᭤⥺㸦Fig. 28A㸧ࢆᮾ࢔ࢪ࢔ࡢⓑள⣖ࡢ௦⾲ⓗ࡞ሁ✚┅࡜ẚ㍑ࡍࡿ

࡜㸪࿴Ἠሁ✚┅ࡢỿ㝆㛤ጞ᫬ᮇࡸୖ᪼ࡢ᫬ᮇࡀ኱㝣⦕㎶㒊ࡢ௚ࡢᶓࡎࢀሁ✚┅࡜୍⮴ࡋ࡚

࠸࡞࠸㸦Fig. 29㸧㸬࠾ࡑࡽࡃ㸪࿴Ἠሁ✚┅ࡢᙧᡂⓎ㐩࡟ࡣ㸪ఱࡽ࠿ࡢᆅᇦⓗ࡞ࢸࢡࢺࢽࢡࢫ ࡀ኱ࡁࡃᙳ㡪ࡋ࡚࠸ࡓࡢࡔࢁ࠺㸬➨㸲❶࡛㆟ㄽࡋࡓ࡜࠾ࡾ㸪࿴Ἠᖏࡢỿ㝆࡜ୖ᪼࡟ࡣ㸪MTL ࡢᶓࡎࢀ㐠ືࡀ」㞧࡟㛵㐃ࡋࡓᛂຊሙࡢኚ㑄ࡀ㛵୚ࡋ࡚࠸ࡓྍ⬟ᛶࡀ࠶ࡿ㸬

㸳㸬㸰 ᇙἐࡢᩘ್ࣔࢹࣝࢩ࣑࣮ࣗࣞࢩࣙࣥ

㸳㸬㸰㸬㸯 ཎ⌮

ᮏ◊✲࡛ࡣ㸪ሁ✚┅࡛ࡢᛴ㏿࡞ỿ㝆ࡀࡶࡓࡽࡍ ᗘ≧ែ࡜ୖ᪼᫬ࡢ ᗘ≧ែཬࡧ⇍ᡂ≧

ែࡢኚ໬࡟ࡘ࠸࡚㸪ᩘ್ࣔࢹ࡛ࣝ᚟ඖࡍࡿࡇ࡜ࢆ┠ⓗ࡜ࡋ࡚ࢩ࣑࣮ࣗࣞࢩࣙࣥࣉࣟࢢ࣒ࣛ

ࡢసᡂ࡜ࣔࢹࣝィ⟬ࢆᐇ᪋ࡋࡓ㸬

Hutchison㸦1985㸧ࡣᾏὒࣉ࣮ࣞࢺୖࡢሁ✚≀ࡢᆅẆ⇕ὶ㔞࡟ሁ✚≀ࡢᇙ✚ࡀཬࡰࡍᙳ

㡪ࢆᩘ್ࣔࢹࣝ࡟ࡼࡾ᫂ࡽ࠿࡟ࡋࡓ㸬㖄┤᪉ྥ࡟ఙࡧࡿሁ✚≀ᰕࡢdz_{✵㛫࡟࠾ࡅࡿ㉁㔞ಖ} Ꮡࡢἲ๎࠾ࡼࡧୖ㠃࡜ᗏ㠃ࡢ⇕㔞ࡢ཰ᨭࡼࡾ㸪㖄┤᪉ྥ࡟≀㉁ࡀ㏿ᗘ V_㸦㹫࣭s^-1㸧࡛⛣ື

ࡍࡿሙྜࡢ୍ḟඖ⇕ᣑᩓ᪉⛬ᘧࡣ௨ୗࡢࡼ࠺࡟⾲⌧࡛ࡁࡿ㸦2.1ᘧ㸧㸬

) 1 . 2 ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ( ࠉࠉࠉࠉࠉࠉࠉࠉࠉࠉ

z A T z CV z

K T z t T t

C

w w w w w w w

w w w w

wU U

 ᗘT㸦K㸧㸪᫬㛫t㸦s㸧㸪㖄┤᪉ྥࡢᗙᶆz㸦㹫㸧㸪ρ_{ࡣ≀㉁ࡢẚ㔜㸦}kg࣭m^-3㸧㸪Kࡣ⇕ఏᑟ

⋡㸦W࣭m^-1࣭K^-1㸧㸪Cࡣẚ⇕ᐜ㔞㸦J࣭kg^-1࣭K^-1㸧࡛࠶ࡾρCࡀ༢఩య✚࠶ࡓࡾࡢ⇕ᐜ㔞࡛࠶

ࡿ㸬A㸦W࣭m^-3㸧ࡣ⇕⏕⏘࡛㸪ᒾ▼ࡢሙྜࡣෆ㒊࡟ྵࡲࢀࡿᨺᑕᛶ᰾✀ࡢቯኚ࡟ࡼࡾⓎ⏕ࡍ

ࡿ⇕㔞ࡀヱᙜࡍࡿ㸬ρCࡣ᫬㛫ࡢ೫ᚤศ࡟㛵ࡋ࡚㏻ᖖࡣᐃᩘ࡜ࡋ࡚ᢅ࠼ࡿ㸬

Hutchison㸦1985㸧ࡣ㸪ᇶ┙ᒾୖ࡟ሁ✚ࡋࡓሁ✚≀ࡢ㖄┤᪉ྥ࡬ࡢ⛣ື࡟㛵ࡋ࡚௨ୗࡢ2

ᘧࢆ⏝࠸࡚࠸ࡿ㸦2.2࠾ࡼࡧ2.3ᘧ㸧㸬 㸦ሁ✚≀ࡢᇙἐ᫬㸧

>

₁

@ >

¹

@

_{Aࠉࠉࠉ(2.2)}

z T z

V C V

C z

K T z t C T

C_{W S S W S} ^{W W W S S S}

W

w w w

w w w w

w w w

U I U I U I

I U

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