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NARROW
GeoRef Subject
-
all geography including DSDP/ODP Sites and Legs
-
Africa
-
North Africa
-
Tunisia
-
El Kef Tunisia (1)
-
-
-
Southern Africa
-
Namibia (1)
-
-
-
Antarctica
-
Amundsen Sea (1)
-
Antarctic ice sheet (1)
-
East Antarctica (3)
-
South Shetland Islands
-
Deception Island (1)
-
-
-
Asia
-
Far East
-
China
-
Yunnan China (1)
-
-
Japan
-
Hokkaido (1)
-
-
-
Indian Peninsula
-
India
-
Cauvery Basin (1)
-
Damodar Valley (1)
-
Deccan Plateau (1)
-
Jharkhand India (1)
-
West Bengal India
-
Raniganj India (1)
-
-
-
Indian Shield (1)
-
-
Popigay Structure (1)
-
-
Atlantic Ocean
-
North Atlantic
-
Blake Plateau
-
Blake Nose (3)
-
-
Labrador Sea (1)
-
Northeast Atlantic
-
Iberian abyssal plain (2)
-
-
Rockall Plateau (1)
-
-
South Atlantic
-
Angola Basin (1)
-
Southwest Atlantic (1)
-
Walvis Ridge (1)
-
-
-
Australasia
-
Australia (1)
-
New Zealand (1)
-
-
Broken Ridge (4)
-
Commonwealth of Independent States
-
Russian Federation
-
Popigay Structure (1)
-
-
-
East Pacific Ocean Islands
-
Hawaii (2)
-
-
Europe
-
Southern Europe
-
Italy
-
Umbria Italy
-
Perugia Italy
-
Gubbio Italy (1)
-
-
-
-
-
Western Europe
-
Iceland (1)
-
Scandinavia
-
Denmark (1)
-
-
-
-
Georgia Basin (1)
-
Hudson Canyon (1)
-
Indian Ocean
-
Arabian Sea (1)
-
Exmouth Plateau (4)
-
Mid-Indian Ridge
-
Southeast Indian Ridge (2)
-
-
Naturaliste Plateau (2)
-
Ninetyeast Ridge (5)
-
Wharton Basin (1)
-
Wombat Plateau (2)
-
-
Indian Ocean Islands
-
Kerguelen Islands (2)
-
-
International Ocean Discovery Program
-
Expedition 353
-
IODP Site U1443 (1)
-
-
-
Kerguelen Plateau (53)
-
Krishna-Godavari Basin (1)
-
North Island (1)
-
Oceania
-
Polynesia
-
Hawaii (2)
-
-
-
Pacific Ocean
-
East Pacific
-
Northeast Pacific (4)
-
Southeast Pacific
-
Nazca Ridge (1)
-
-
-
Equatorial Pacific (4)
-
North Pacific
-
Mid-Pacific Mountains
-
Resolution Seamount (1)
-
-
Northeast Pacific (4)
-
Northwest Pacific
-
Emperor Seamounts (1)
-
Shatsky Rise (2)
-
South China Sea (1)
-
-
-
South Pacific
-
Southeast Pacific
-
Nazca Ridge (1)
-
-
Southwest Pacific
-
Campbell Plateau (1)
-
Lord Howe Rise (1)
-
Tasman Sea (3)
-
-
-
West Pacific
-
Northwest Pacific
-
Emperor Seamounts (1)
-
Shatsky Rise (2)
-
South China Sea (1)
-
-
Ontong Java Plateau (4)
-
Resolution Seamount (1)
-
Southwest Pacific
-
Campbell Plateau (1)
-
Lord Howe Rise (1)
-
Tasman Sea (3)
-
-
-
-
Scotia Sea Islands
-
South Shetland Islands
-
Deception Island (1)
-
-
-
Southern Ocean
-
Prydz Bay (1)
-
Ross Sea
-
McMurdo Sound (1)
-
-
Weddell Sea
-
Maud Rise (13)
-
-
-
United States
-
Columbia Plateau (1)
-
Hawaii (2)
-
-
-
elements, isotopes
-
carbon
-
C-13/C-12 (7)
-
-
isotope ratios (12)
-
isotopes
-
radioactive isotopes
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
Rb-87/Sr-86 (1)
-
-
stable isotopes
-
C-13/C-12 (7)
-
Nd-144/Nd-143 (2)
-
O-18/O-16 (9)
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
Rb-87/Sr-86 (1)
-
Sr-87/Sr-86 (3)
-
-
-
metals
-
alkali metals
-
rubidium
-
Rb-87/Sr-86 (1)
-
-
-
alkaline earth metals
-
strontium
-
Rb-87/Sr-86 (1)
-
Sr-87/Sr-86 (3)
-
-
-
lead
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
-
platinum group
-
iridium (1)
-
-
rare earths
-
neodymium
-
Nd-144/Nd-143 (2)
-
-
-
-
oxygen
-
O-18/O-16 (9)
-
-
-
fossils
-
Invertebrata
-
Arthropoda
-
Mandibulata
-
Crustacea
-
Ostracoda (2)
-
-
-
-
Mollusca
-
Bivalvia (1)
-
-
Protista
-
Foraminifera
-
Rotaliina
-
Cassidulinacea
-
Anomalinidae
-
Cibicidoides (1)
-
-
-
-
-
Radiolaria
-
Osculosida
-
Nassellina (3)
-
-
Spumellina (2)
-
-
-
-
microfossils (28)
-
palynomorphs
-
Dinoflagellata (1)
-
-
Plantae
-
algae
-
diatoms (2)
-
nannofossils (3)
-
-
-
thallophytes (2)
-
-
geochronology methods
-
Ar/Ar (4)
-
paleomagnetism (1)
-
Pb/Pb (1)
-
U/Pb (1)
-
-
geologic age
-
Cenozoic
-
Quaternary
-
Pleistocene (1)
-
-
Tertiary
-
Neogene
-
Miocene
-
Columbia River Basalt Group (1)
-
middle Miocene (1)
-
-
Pliocene
-
lower Pliocene (1)
-
-
-
Paleogene
-
Eocene
-
lower Eocene (1)
-
middle Eocene (2)
-
upper Eocene (3)
-
-
lower Paleogene (1)
-
Oligocene
-
lower Oligocene (2)
-
-
Paleocene
-
lower Paleocene
-
Danian (1)
-
K-T boundary (3)
-
-
-
Paleocene-Eocene Thermal Maximum (2)
-
-
-
-
Mesozoic
-
Cretaceous
-
Lower Cretaceous (2)
-
Middle Cretaceous (2)
-
Upper Cretaceous
-
Campanian (1)
-
Cenomanian (1)
-
Coniacian (1)
-
K-T boundary (3)
-
Maestrichtian
-
lower Maestrichtian (1)
-
-
Santonian (1)
-
Senonian (3)
-
Turonian (2)
-
-
-
-
Precambrian
-
upper Precambrian
-
Proterozoic (1)
-
-
-
-
igneous rocks
-
igneous rocks
-
plutonic rocks
-
diabase (1)
-
lamproite (1)
-
-
volcanic rocks
-
basalts
-
flood basalts (2)
-
mid-ocean ridge basalts (1)
-
tholeiite (1)
-
-
pyroclastics (1)
-
rhyolites (1)
-
trachytes (1)
-
-
-
-
metamorphic rocks
-
metamorphic rocks
-
gneisses
-
biotite gneiss (1)
-
-
-
-
minerals
-
phosphates
-
monazite (1)
-
-
silicates
-
chain silicates
-
pyroxene group
-
clinopyroxene (1)
-
-
-
framework silicates
-
silica minerals
-
coesite (1)
-
quartz (1)
-
-
-
orthosilicates
-
nesosilicates
-
zircon group
-
zircon (1)
-
-
-
-
-
-
Primary terms
-
absolute age (5)
-
Africa
-
North Africa
-
Tunisia
-
El Kef Tunisia (1)
-
-
-
Southern Africa
-
Namibia (1)
-
-
-
Antarctica
-
Amundsen Sea (1)
-
Antarctic ice sheet (1)
-
East Antarctica (3)
-
South Shetland Islands
-
Deception Island (1)
-
-
-
Asia
-
Far East
-
China
-
Yunnan China (1)
-
-
Japan
-
Hokkaido (1)
-
-
-
Indian Peninsula
-
India
-
Cauvery Basin (1)
-
Damodar Valley (1)
-
Deccan Plateau (1)
-
Jharkhand India (1)
-
West Bengal India
-
Raniganj India (1)
-
-
-
Indian Shield (1)
-
-
Popigay Structure (1)
-
-
Atlantic Ocean
-
North Atlantic
-
Blake Plateau
-
Blake Nose (3)
-
-
Labrador Sea (1)
-
Northeast Atlantic
-
Iberian abyssal plain (2)
-
-
Rockall Plateau (1)
-
-
South Atlantic
-
Angola Basin (1)
-
Southwest Atlantic (1)
-
Walvis Ridge (1)
-
-
-
Australasia
-
Australia (1)
-
New Zealand (1)
-
-
biogeography (3)
-
carbon
-
C-13/C-12 (7)
-
-
Cenozoic
-
Quaternary
-
Pleistocene (1)
-
-
Tertiary
-
Neogene
-
Miocene
-
Columbia River Basalt Group (1)
-
middle Miocene (1)
-
-
Pliocene
-
lower Pliocene (1)
-
-
-
Paleogene
-
Eocene
-
lower Eocene (1)
-
middle Eocene (2)
-
upper Eocene (3)
-
-
lower Paleogene (1)
-
Oligocene
-
lower Oligocene (2)
-
-
Paleocene
-
lower Paleocene
-
Danian (1)
-
K-T boundary (3)
-
-
-
Paleocene-Eocene Thermal Maximum (2)
-
-
-
-
climate change (4)
-
continental drift (3)
-
crust (8)
-
data processing (1)
-
Deep Sea Drilling Project
-
IPOD
-
Leg 48
-
DSDP Site 400 (1)
-
-
Leg 62
-
DSDP Site 463 (2)
-
-
Leg 72
-
DSDP Site 516 (1)
-
-
Leg 73
-
DSDP Site 522 (1)
-
-
Leg 74
-
DSDP Site 525 (1)
-
DSDP Site 526 (1)
-
-
Leg 78A
-
DSDP Site 543 (1)
-
-
Leg 80
-
DSDP Site 549 (1)
-
-
Leg 81
-
DSDP Site 553 (1)
-
-
Leg 90
-
DSDP Site 592 (1)
-
-
Leg 93
-
DSDP Site 605 (1)
-
-
Leg 94
-
DSDP Site 607 (1)
-
DSDP Site 610 (1)
-
-
-
Leg 12
-
DSDP Site 111 (1)
-
-
Leg 14
-
DSDP Site 138 (1)
-
-
Leg 17
-
DSDP Site 167 (1)
-
-
Leg 21
-
DSDP Site 207 (1)
-
DSDP Site 208 (1)
-
DSDP Site 209 (1)
-
-
Leg 24
-
DSDP Site 237 (1)
-
-
Leg 26
-
DSDP Site 253 (1)
-
DSDP Site 254 (1)
-
DSDP Site 258 (1)
-
-
Leg 28
-
DSDP Site 264 (1)
-
-
Leg 29
-
DSDP Site 277 (1)
-
DSDP Site 278 (1)
-
DSDP Site 280 (1)
-
DSDP Site 281 (1)
-
-
Leg 33 (1)
-
Leg 36
-
DSDP Site 328 (1)
-
-
Leg 39
-
DSDP Site 357 (1)
-
-
Leg 40
-
DSDP Site 362 (1)
-
-
Leg 6
-
DSDP Site 44 (1)
-
-
-
Earth (1)
-
earthquakes (1)
-
East Pacific Ocean Islands
-
Hawaii (2)
-
-
ecology (1)
-
Europe
-
Southern Europe
-
Italy
-
Umbria Italy
-
Perugia Italy
-
Gubbio Italy (1)
-
-
-
-
-
Western Europe
-
Iceland (1)
-
Scandinavia
-
Denmark (1)
-
-
-
-
faults (2)
-
fractures (1)
-
geochemistry (1)
-
geophysical methods (6)
-
glacial geology (2)
-
igneous rocks
-
plutonic rocks
-
diabase (1)
-
lamproite (1)
-
-
volcanic rocks
-
basalts
-
flood basalts (2)
-
mid-ocean ridge basalts (1)
-
tholeiite (1)
-
-
pyroclastics (1)
-
rhyolites (1)
-
trachytes (1)
-
-
-
inclusions (1)
-
Indian Ocean
-
Arabian Sea (1)
-
Exmouth Plateau (4)
-
Mid-Indian Ridge
-
Southeast Indian Ridge (2)
-
-
Naturaliste Plateau (2)
-
Ninetyeast Ridge (5)
-
Wharton Basin (1)
-
Wombat Plateau (2)
-
-
Indian Ocean Islands
-
Kerguelen Islands (2)
-
-
Integrated Ocean Drilling Program
-
Expedition 318 (1)
-
Expeditions 320/321
-
Expedition 321
-
IODP Site U1337 (1)
-
IODP Site U1338 (1)
-
-
-
-
intrusions (1)
-
Invertebrata
-
Arthropoda
-
Mandibulata
-
Crustacea
-
Ostracoda (2)
-
-
-
-
Mollusca
-
Bivalvia (1)
-
-
Protista
-
Foraminifera
-
Rotaliina
-
Cassidulinacea
-
Anomalinidae
-
Cibicidoides (1)
-
-
-
-
-
Radiolaria
-
Osculosida
-
Nassellina (3)
-
-
Spumellina (2)
-
-
-
-
isotopes
-
radioactive isotopes
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
Rb-87/Sr-86 (1)
-
-
stable isotopes
-
C-13/C-12 (7)
-
Nd-144/Nd-143 (2)
-
O-18/O-16 (9)
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
Rb-87/Sr-86 (1)
-
Sr-87/Sr-86 (3)
-
-
-
lava (4)
-
magmas (4)
-
mantle (6)
-
Mesozoic
-
Cretaceous
-
Lower Cretaceous (2)
-
Middle Cretaceous (2)
-
Upper Cretaceous
-
Campanian (1)
-
Cenomanian (1)
-
Coniacian (1)
-
K-T boundary (3)
-
Maestrichtian
-
lower Maestrichtian (1)
-
-
Santonian (1)
-
Senonian (3)
-
Turonian (2)
-
-
-
-
metals
-
alkali metals
-
rubidium
-
Rb-87/Sr-86 (1)
-
-
-
alkaline earth metals
-
strontium
-
Rb-87/Sr-86 (1)
-
Sr-87/Sr-86 (3)
-
-
-
lead
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
-
platinum group
-
iridium (1)
-
-
rare earths
-
neodymium
-
Nd-144/Nd-143 (2)
-
-
-
-
metamorphic rocks
-
gneisses
-
biotite gneiss (1)
-
-
-
metamorphism (1)
-
ocean basins (1)
-
Ocean Drilling Program
-
Leg 105
-
ODP Site 647 (1)
-
-
Leg 110
-
ODP Site 672 (1)
-
ODP Site 674 (1)
-
-
Leg 112
-
ODP Site 688 (1)
-
-
Leg 113
-
ODP Site 689 (10)
-
ODP Site 690 (12)
-
ODP Site 693 (4)
-
-
Leg 114
-
ODP Site 698 (2)
-
ODP Site 699 (2)
-
ODP Site 700 (2)
-
ODP Site 702 (2)
-
ODP Site 703 (2)
-
-
Leg 115
-
ODP Site 709 (1)
-
-
Leg 117
-
ODP Site 722 (1)
-
-
Leg 119
-
ODP Site 737 (4)
-
ODP Site 738 (14)
-
ODP Site 744 (12)
-
ODP Site 745 (6)
-
ODP Site 746 (5)
-
-
Leg 120
-
ODP Site 747 (7)
-
ODP Site 748 (14)
-
ODP Site 749 (2)
-
ODP Site 750 (5)
-
ODP Site 751 (6)
-
-
Leg 121
-
ODP Site 752 (1)
-
ODP Site 757 (1)
-
ODP Site 758 (3)
-
-
Leg 122
-
ODP Site 761 (3)
-
ODP Site 762 (2)
-
ODP Site 763 (2)
-
-
Leg 125
-
ODP Site 782 (1)
-
ODP Site 786 (1)
-
-
Leg 130
-
ODP Site 807 (1)
-
-
Leg 132
-
ODP Site 810 (1)
-
-
Leg 143
-
ODP Site 866 (1)
-
-
Leg 145
-
ODP Site 884 (1)
-
-
Leg 149
-
ODP Site 897 (1)
-
ODP Site 900 (1)
-
-
Leg 171B
-
ODP Site 1049 (1)
-
ODP Site 1050 (1)
-
ODP Site 1051 (1)
-
ODP Site 1052 (1)
-
ODP Site 1053 (1)
-
-
Leg 174A
-
ODP Site 1073 (1)
-
-
Leg 177
-
ODP Site 1090 (1)
-
-
Leg 183
-
ODP Site 1135 (1)
-
ODP Site 1136 (2)
-
ODP Site 1137 (4)
-
ODP Site 1138 (6)
-
ODP Site 1141 (1)
-
ODP Site 1142 (1)
-
-
Leg 184
-
ODP Site 1146 (1)
-
-
Leg 189
-
ODP Site 1171 (1)
-
-
Leg 198
-
ODP Site 1209 (2)
-
ODP Site 1210 (1)
-
ODP Site 1211 (1)
-
ODP Site 1212 (1)
-
-
Leg 199
-
ODP Site 1218 (1)
-
ODP Site 1220 (1)
-
-
Leg 202
-
ODP Site 1236 (1)
-
ODP Site 1237 (1)
-
-
-
ocean floors (7)
-
Oceania
-
Polynesia
-
Hawaii (2)
-
-
-
oceanography (2)
-
oxygen
-
O-18/O-16 (9)
-
-
Pacific Ocean
-
East Pacific
-
Northeast Pacific (4)
-
Southeast Pacific
-
Nazca Ridge (1)
-
-
-
Equatorial Pacific (4)
-
North Pacific
-
Mid-Pacific Mountains
-
Resolution Seamount (1)
-
-
Northeast Pacific (4)
-
Northwest Pacific
-
Emperor Seamounts (1)
-
Shatsky Rise (2)
-
South China Sea (1)
-
-
-
South Pacific
-
Southeast Pacific
-
Nazca Ridge (1)
-
-
Southwest Pacific
-
Campbell Plateau (1)
-
Lord Howe Rise (1)
-
Tasman Sea (3)
-
-
-
West Pacific
-
Northwest Pacific
-
Emperor Seamounts (1)
-
Shatsky Rise (2)
-
South China Sea (1)
-
-
Ontong Java Plateau (4)
-
Resolution Seamount (1)
-
Southwest Pacific
-
Campbell Plateau (1)
-
Lord Howe Rise (1)
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Tasman Sea (3)
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Kerguelen Plateau
Astronomically forced climate variability across the Eocene–Oligocene transition from a low latitude terrestrial record (Lühe Basin, South China)
Middle Miocene climate–carbon cycle dynamics: Keys for understanding future trends on a warmer Earth?
ABSTRACT The late early to middle Miocene period (18–12.7 Ma) was marked by profound environmental change, as Earth entered into the warmest climate phase of the Neogene (Miocene climate optimum) and then transitioned to a much colder mode with development of permanent ice sheets on Antarctica. Integration of high-resolution benthic foraminiferal isotope records in well-preserved sedimentary successions from the Pacific, Southern, and Indian Oceans provides a long-term perspective with which to assess relationships among climate change, ocean circulation, and carbon cycle dynamics during these successive climate reversals. Fundamentally different modes of ocean circulation and carbon cycling prevailed on an almost ice-free Earth during the Miocene climate optimum (ca. 16.9–14.7 Ma). Comparison of δ 13 C profiles revealed a marked decrease in ocean stratification and in the strength of the meridional overturning circulation during the Miocene climate optimum. We speculate that labile polar ice sheets, weaker Southern Hemisphere westerlies, higher sea level, and more acidic, oxygen-depleted oceans promoted shelf-basin partitioning of carbonate deposition and a weaker meridional overturning circulation, reducing the sequestration efficiency of the biological pump. X-ray fluorescence scanning data additionally revealed that 100 k.y. eccentricity-paced transient hyperthermal events coincided with intense episodes of deep-water acidification and deoxygenation. The in-phase coherence of δ 18 O and δ 13 C at the eccentricity band further suggests that orbitally paced processes such as remineralization of organic carbon from the deep-ocean dissolved organic carbon pool and/or weathering-induced carbon and nutrient fluxes from tropical monsoonal regions to the ocean contributed to the high amplitude variability of the marine carbon cycle. Stepwise global cooling and ice-sheet expansion during the middle Miocene climate transition (ca. 14.7–13.8 Ma) were associated with dampening of astronomically driven climate cycles and progressive steepening of the δ 13 C gradient between intermediate and deep waters, indicating intensification and vertical expansion of ocean meridional overturning circulation following the end of the Miocene climate optimum. Together, these results underline the crucial role of the marine carbon cycle and low-latitude processes in driving climate dynamics on an almost ice-free Earth.
Off-sequence plume magmatism near Ninetyeast Ridge in the Indian Ocean: evidence for extensive lateral flow of the Kerguelen plume
Chapter 5.5 Gaussberg: volcanology and petrology
Abstract Gaussberg is a nunatak composed of lamproite pillow lava situated on the coast of East Antarctica. It is the most isolated Quaternary volcanic centre in Antarctica but it is important palaeoenvironmentally and petrologically out of all proportion to its small size. The edifice has a likely low, shield-like, morphology c. 1200 m high and possibly up to 10 km wide, which is unusually large for a lamproite construct. Gaussberg was erupted subglacially at 56 ± 5 ka, which places it late in the last glacial, close to the peak of marine isotope stage 3. The coeval ice sheet was c. 1300 m thick, and c. 420 m has been removed from the ice surface since Gaussberg erupted. Lamproite is a rare ultrapotassic mantle-derived magma, and Gaussberg is one of two type examples worldwide. Although traditionally considered as related in some way to the Kerguelen plume, it is more likely that the Gaussberg magma is a product of a separate magmatic event. It is ascribed to the storage and long-term (Gy) isolation of sediment emplaced by subduction in the Transition Zone of the deep mantle, followed by entrainment and subsequent melting in a plume.
Abstract We review here data and information on Antarctic volcanism resulting from recent tephrostratigraphic investigations on marine cores. Records include deep drill cores recovered during oceanographic expeditions: DSDP, ODP and IODP drill cores recovered during ice-based and land-based international cooperative drilling programmes DVDP 15, MSSTS-1, CIROS-1 and CIROS-2, DVDP 15, CRP-1, CRP-2/2A and CRP-3, ANDRILL-MIS and ANDRILL-SMS, and shallow gravity and piston cores recovered in the Antarctic and sub-Antarctic oceans. We report on the identification of visible volcaniclastic horizons and, in particular, of primary tephra within the marine sequences. Where available, the results of analyses carried out on these products are presented. The volcanic material identified differs in its nature, composition and emplacement mechanisms. It was derived from different sources on the Antarctic continent and was emplaced over a wide time span. Marine sediments contain a more complete record of the explosive activity from Antarctic volcanoes and are complementary to those obtained by land-based studies. This record provides important information for volcanological reconstructions including approximate intensities and magnitudes of eruptions, and their duration, age and recurrence, as well as their eruptive dynamics. In addition, characterized tephra layers represent an invaluable chronological tool essential in establishing correlations between different archives and in synchronizing climate records.
Large-scale asymmetry in thickness of crustal accretion at the Southeast Indian Ridge due to deep mantle anomalies
Longest continuously erupting large igneous province driven by plume-ridge interaction
The 4 December 2015 M w 7.1 Normal‐Faulting Antarctic Plate Earthquake and Its Seismotectonic Implications
Nature of Cretaceous dolerite dikes with two distinct trends in the Damodar Valley, eastern India: Constraints on their linkage to mantle plumes and large igneous provinces from 40 Ar/ 39 Ar geochronology and geochemistry
Southern Hemisphere sea-surface temperatures during the Cenomanian–Turonian: Implications for the termination of Oceanic Anoxic Event 2
Abstract The Elan Bank microcontinent was separated from East India during the Early Cretaceous break-up. The crustal architecture and rifting geometry of East India and the Elan Bank margins document that the early break-up between India and Antarctica was initiated in the eastern portions of the Cauvery and Krishna–Godavari rift zones, and in the southern portion of Elan Bank. However, the westwards break-up propagation along the Krishna–Godavari Rift Zone continued even after the break-up in the overstepping portion of the Cauvery Rift Zone. Eventually, the western propagating end of the Krishna–Godavari Rift Zone became hard-linked with the failed western portion of the Cauvery Rift Zone by the dextral Coromandel transfer fault zone. Consequently, the break-up location between India and Antarctica shifted from its initial to its final location along the northern portion of the Elan Bank formed by the western Krishna–Godavari Rift Zone. The competition between the two rift zones to capture continental break-up and asymmetric ridge propagation resulted in a ridge jump and the Elan Bank microcontinent release.
New species of Neogene radiolarians from the Southern Ocean – part IV
New species of Neogene radiolarians from the Southern Ocean – part III
The mid-Cretaceous was marked by emplacement of large igneous provinces (LIPs) that formed gigantic oceanic plateaus, affecting ecosystems on a global scale, with biota forced to face excess CO 2 resulting in climate and ocean perturbations. Volcanic phases of the Ontong Java Plateau (OJP) and the southern Kerguelen Plateau (SKP) are radiometrically dated and correlate with paleoenvironmental changes, suggesting causal links between LIPs and ecosystem responses. Aptian biocalcification crises and recoveries are broadly coeval with C, Pb, and Os isotopic anomalies, trace metal influxes, global anoxia, and climate changes. Early Aptian greenhouse or super-greenhouse conditions were followed by prolonged cooling during the late Aptian, when OJP and SKP developed, respectively. Massive volcanism occurring at equatorial versus high paleolatitudes and submarine versus subaerial settings triggered very different climate responses but similar disruptions in the marine carbonate system. Excess CO 2 arguably induced episodic ocean acidification that was detrimental to marine calcifiers, regardless of hot or cool conditions. Global anoxia was reached only under extreme warming, whereas cold conditions kept the oceans well oxygenated even at times of intensified fertility. The environmental disruptions attributed to the OJP did not trigger a mass extinction: rock-forming nannoconids and benthic communities underwent a significant decline during Oceanic Anoxic Event (OAE) 1a, but recovered when paroxysmal volcanism finished. Extinction of many planktonic foraminiferal and nannoplankton taxa, including most nannoconids, and most aragonitic rudists in latest Aptian time was likely triggered by severe ocean acidification. Upgraded dating of paleoceanographic events, improved radiometric ages of the OJP and SKP, and time-scale revision are needed to substantiate the links between magmatism and paleoenvironmental perturbations.