Late Tertiary Climate and its Relation to Fan Formation

1984 ◽  
Author(s):  
Allen Lowrie
Keyword(s):  
Late Tertiary

Molecular phylogeny and divergence time estimates of Penaeid Shrimp Lineages (Decapoda: Penaeidae)

Zootaxa ◽  
2009 ◽  
Vol 2107 (1) ◽  
pp. 41-52 ◽  
Author(s):  
CAROLINA M VOLOCH ◽  
PABLO R FREIRE ◽  
CLAUDIA A M RUSSO
Keyword(s):  
Fossil Record ◽  
Divergence Time ◽  
Penaeid Shrimp ◽  
Divergence Time Estimates ◽  
Time Estimates ◽  
Global Clock ◽  
Late Tertiary ◽  
The Family ◽  
Molecular Studies ◽  
Triassic Period

Fossil record of penaeids indicates that the family exists since the Triassic period, but extant genera appeared only recently in Tertiary strata. Molecular based divergence time estimates on the matter of penaeid radiation were never properly addressed, due to shortcomings of the global molecular clock assumptions. Here, we studied the diversification patterns of the family, uncovering, more specifically, a correlation between fossil and extant Penaeid fauna. For this, we have used a Bayesian framework that does not assume a global clock. Our results suggest that Penaeid genera originated between 20 million years ago and 43 million years ago, much earlier than expected by previous molecular studies. Altogether, these results promptly discard late Tertiary or even Quaternary hypotheses that presumed a major glaciations influence on the diversification patterns of the family.

scholarly journals The Fundamental Stratigraphy of the Late Tertiary Kiyosumi and the Anno Formations along the Inokawa River in the Central Boso Peninsula

1980 ◽  
Vol 89 (2) ◽  
pp. 113-123
Author(s):  
Shiro MAEDA ◽  
Yoshioki WATANABE ◽  
Sumio OHTSUKA ◽  
Tetsuya KAWABE
Keyword(s):  
Boso Peninsula ◽  
Late Tertiary

A heat-flow reconnaissance of southeastern Alaska

1985 ◽  
Vol 22 (3) ◽  
pp. 416-421 ◽  
Author(s):  
J. H. Sass ◽  
L. A. Lawver ◽  
R. J. Munroe
Keyword(s):  
Heat Flow ◽  
Plate Boundary ◽  
Thermal Spring ◽  
High Heat ◽  
Transform Fault ◽  
High Heat Flow ◽  
Queen Charlotte Islands ◽  
Late Tertiary ◽  
The Mean ◽  
Strain Heating

Heat flow was measured at nine sites in crystalline and sedimentary rocks of southeastern Alaska. Seven of the sites, located between 115 and 155 km landward of the Queen Charlotte – Fairweather transform fault, have an average heat flow of 59 ± 6 mW m−2. This value is significantly higher than the mean of 42 mW m−2 in the coastal provinces between Cape Mendocino and the Queen Charlotte Islands, to the south, and is lower than the mean of 72 ± 2 mW m−2 for 81 values within 100 km of the San Andreas transform fault, even farther south. This intermediate value suggests the absence of significant heat sinks associated with Cenozoic subduction and of heat sources related to either late Cenozoic tectono-magmatic events or significant shear-strain heating. At Warm Springs Bay, 75 km from the plate boundary, an anomalously high heat flow of 150 mW m−2 can most plausibly be ascribed to the thermal spring activity from which its name is derived. At Quartz Hill, 240 km landward of the plate boundary, a value of 115 mW m−2 might indicate a transition to a province of high heat flow resulting from late Tertiary and Quaternary extension and volcanism.

Emplacement ages and exhumation rates for intrusion-hosted Cu–Mo–Sb–Au mineral systems at Freegold Mountain (Yukon, Canada): assessment from U–Pb, Ar–Ar, and (U–Th)/He geochronometers

2012 ◽  
Vol 49 (5) ◽  
pp. 653-670 ◽  
Author(s):  
Thierry Bineli Betsi ◽  
David Lentz ◽  
Brent McInnes ◽  
Noreen J. Evans
Keyword(s):  
Hydrothermal Systems ◽  
Mountain Area ◽  
Erosion Rates ◽  
Late Tertiary ◽  
History Of ◽  
Fast Cooling ◽  
Exhumation Rates ◽  
Uplift And Erosion ◽  
Combined Data ◽  
Hydrothermal Event

To decipher the thermal history of mineralized systems across the Freegold Mountain area (Yukon, Canada), a combined geochronology (zircon U–Pb and hornblende, biotite, and whole rock Ar–Ar) and thermochronology (apatite and zircon (U–Th)/He) study was carried out. Previous U–Pb data combined with new U–Pb and Ar–Ar data show that intrusive bodies across the Freegold Mountain were emplaced during two protracted episodes, the first spanning from 109.6 to 98 Ma and the second between 79 and 68 Ma. Overprinting of the first intrusive event by a second magmatic hydrothermal event is suggested by a zircon U–Pb age of 108.7 ± 0.4 Ma for a chlorite-altered dyke and a whole rock Ar–Ar plateau age of 76.25 ± 0.53 Ma. Zircon (U–Th)/He data are between 66 and 89 Ma, whereas apatite (U–Th)/He data are scattered (38.7–109.9 Ma) and bracket the two magmatic emplacement events. Our combined data reveal a complex history of reheating that led to resetting of numerous chronometers. In most of the investigated magmatic hydrothermal systems, early fast cooling from igneous emplacement through hydrothermal alteration (between 900 and 200 °C) was followed by later and slower cooling accompanying post mineralization uplift and erosion (between 200 and 70 °C). Preliminary models indicate intrusive bodies associated with the Stoddart Cu–Mo ± W prospect cooled slowly (23 °C/Ma) compared with the ones spatially associated with the Revenue Au–Cu prospect (43 °C/Ma), and the similarity of the zircon U–Pb and (U–Th)/He ages from Revenue dyke further supports a rapid cooling from 700 to 180 °C. Erosion rates of 0.035–0.045 mm/year are consistent with tectonic quiescence during the Late Tertiary combined with the lack of Pleistocene glaciation in central Yukon. Such low rates of exhumation favour the formation and preservation of supergene mineralization, such as that found north of Freegold Mountain.

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