scholarly journals Stratigraphy of the Eocene–Oligocene Titus Canyon Formation, Death Valley, California, and Eocene extensional tectonism in the Basin and Range

Geosphere ◽  
2021 ◽  
Author(s):  
Nikolas Midttun ◽  
Nathan A. Niemi ◽  
Bianca Gallina
Keyword(s):  
Detrital Zircon ◽  
Convergence Rates ◽  
Plate Boundary ◽  
Basin And Range ◽  
Late Eocene ◽  
Death Valley ◽  
Central Basin ◽  
Geologic Mapping ◽  
Extensional Basin ◽  
Stress Changes

Geologic mapping, measured sections, and geochronologic data elucidate the tectono-stratigraphic development of the Titus Canyon extensional basin in Death Valley, California, and provide new constraints on the age of the Titus Canyon Formation, one of the earliest syn-extensional deposits in the central Basin and Range. Detrital zircon maximum depositional ages (MDAs) and compiled 40Ar/39Ar ages indicate that the Titus Canyon Formation spans 40(?)–30 Ma, consistent with an inferred Duchesnean age for a unique assemblage of mammalian fossils in the lower part of the formation. The Titus Canyon Formation preserves a shift in depositional environment from fluvial to lacustrine at ca. 35 Ma, which along with a change in detrital zircon provenance may reflect both the onset of local extensional tectonism and climatic changes at the Eocene–Oligocene boundary. Our data establish the Titus Canyon basin as the southernmost basin in a system of late Eocene extensional basins that formed along the axis of the Sevier orogenic belt. The distribution of lacustrine deposits in these Eocene basins defines the extent of a low-relief orogenic plateau (Nevadaplano) that occupied eastern Nevada at least through Eocene time. As such, the age and character of Titus Canyon Formation implies that the Nevadaplano extended into the central Basin and Range, ~200 km farther south than previously recognized. Development of the Titus Canyon extensional basin precedes local Farallon slab removal by ca. 20 Ma, implying that other mechanisms, such as plate boundary stress changes due to decreased convergence rates in Eocene time, are a more likely trigger for early extension in the central Basin and Range.

scholarly journals Supplemental Material: Stratigraphy of the Eocene–Oligocene Titus Canyon Formation, Death Valley, California, and Eocene extensional tectonism in the Basin and Range

2021 ◽  
Author(s):  
N. Midttun ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Large Scale ◽  
Analytical Data ◽  
Basin And Range ◽  
Death Valley ◽  
Data Table ◽  
Additional Explanation

<div>Text: Additional explanation of the methods used to recalculate the Ar/Ar ages of Gutenkunst (2006), Saylor and Hodges (1994), and Saylor (1991). Figure S1: Analytical plots recalculated from <sup>40</sup>Ar/<sup>39</sup>Ar data originally produced by Gutenkunst (2006). Figure S2: Scans of a large scale map and seven isochron plots for five samples provided by B. Saylor (personal commun., 2015). Table S1: Detrital zircon U-Pb analytical data. Table S2: Zircon (U‐Th)/He analytical data. Table S3: Analytical data for <sup>40</sup>Ar/<sup>39</sup>Ar ages of Gutenkunst (2006).<br></div>

scholarly journals Supplemental Material: Stratigraphy of the Eocene–Oligocene Titus Canyon Formation, Death Valley, California, and Eocene extensional tectonism in the Basin and Range

2022 ◽  
Author(s):  
N. Midttun ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Large Scale ◽  
Analytical Data ◽  
Basin And Range ◽  
Death Valley ◽  
Data Table ◽  
Additional Explanation

<div>Text: Additional explanation of the methods used to recalculate the Ar/Ar ages of Gutenkunst (2006), Saylor and Hodges (1994), and Saylor (1991). Figure S1: Analytical plots recalculated from <sup>40</sup>Ar/<sup>39</sup>Ar data originally produced by Gutenkunst (2006). Figure S2: Scans of a large scale map and seven isochron plots for five samples provided by B. Saylor (personal commun., 2015). Table S1: Detrital zircon U-Pb analytical data. Table S2: Zircon (U‐Th)/He analytical data. Table S3: Analytical data for <sup>40</sup>Ar/<sup>39</sup>Ar ages of Gutenkunst (2006).<br></div>

Supplemental Material: Stratigraphy of the Eocene–Oligocene Titus Canyon Formation, Death Valley, California, and Eocene extensional tectonism in the Basin and Range

2021 ◽  
Author(s):  
N. Midttun ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Large Scale ◽  
Analytical Data ◽  
Basin And Range ◽  
Death Valley ◽  
Data Table ◽  
Additional Explanation

<div>Text: Additional explanation of the methods used to recalculate the Ar/Ar ages of Gutenkunst (2006), Saylor and Hodges (1994), and Saylor (1991). Figure S1: Analytical plots recalculated from <sup>40</sup>Ar/<sup>39</sup>Ar data originally produced by Gutenkunst (2006). Figure S2: Scans of a large scale map and seven isochron plots for five samples provided by B. Saylor (personal commun., 2015). Table S1: Detrital zircon U-Pb analytical data. Table S2: Zircon (U‐Th)/He analytical data. Table S3: Analytical data for <sup>40</sup>Ar/<sup>39</sup>Ar ages of Gutenkunst (2006).<br></div>

How does the Alpine belt end between Spain and Morocco ?

2002 ◽  
Vol 173 (1) ◽  
pp. 3-15 ◽  
Author(s):  
André Michard ◽  
Ahmed Chalouan ◽  
Hugues Feinberg ◽  
Bruno Goffé ◽  
Raymond Montigny
Keyword(s):  
Subduction Zone ◽  
Plate Boundary ◽  
Western Alps ◽  
Late Eocene ◽  
African Plate ◽  
Northern Margin ◽  
Thrust Tectonics ◽  
Rif Belt ◽  
Transitional Crust ◽  
Roll Back

Abstract The Betic-Rif arcuate mountain belt (southern Spain, northern Morocco) has been interpreted as a symmetrical collisional orogen, partly collapsed through convective removal of its lithospheric mantle root, or else as resulting of the African plate subduction beneath Iberia, with further extension due either to slab break-off or to slab retreat. In both cases, the Betic-Rif orogen would show little continuity with the western Alps. However, it can be recognized in this belt a composite orocline which includes a deformed, exotic terrane, i.e. the Alboran Terrane, thrust through oceanic/transitional crust-floored units onto two distinct plates, i.e. the Iberian and African plates. During the Jurassic-Early Cretaceous, the yet undeformed Alboran Terrane was part of a larger, Alkapeca microcontinent bounded by two arms of the Tethyan-African oceanic domain, alike the Sesia-Margna Austroalpine block further to the northeast. Blueschist- and eclogite-facies metamorphism affected the Alkapeka northern margin and adjacent oceanic crust during the Late Cretaceous-Eocene interval. This testifies the occurrence of a SE-dipping subduction zone which is regarded as the SW projection of the western Alps subduction zone. During the late Eocene-Oligocene, the Alkapeca-Iberia collision triggered back-thrust tectonics, then NW-dipping subduction of the African margin beneath the Alboran Terrane. This Maghrebian-Apenninic subduction resulted in the Mediterranean basin opening, and drifting of the deformed Alkapeca fragments through slab roll back process and back-arc extension, as reported in several publications. In the Gibraltar area, the western tip of the Apenninic-Maghrebian subduction merges with that of the Alpine-Betic subduction zone, and their Neogene roll back resulted in the Alboran Terrane collage astride the Azores-Gibraltar transpressive plate boundary. Therefore, the Betic-Rif belt appears as an asymmetrical, subduction/collision orogen formed through a protracted evolution straightfully related to the Alpine-Apenninic mountain building.

Timing and synchrony of births in bighorn sheep: implications for reintroduction and conservation

2012 ◽  
Vol 39 (7) ◽  
pp. 565 ◽  
Author(s):  
Jericho C. Whiting ◽  
Daniel D. Olson ◽  
Justin M. Shannon ◽  
R. Terry Bowyer ◽  
Robert W. Klaver ◽  
...  
Keyword(s):  
Life History ◽  
Environmental Conditions ◽  
Release Site ◽  
Source Area ◽  
Bighorn Sheep ◽  
Basin And Range ◽  
Central Basin ◽  
Uinta Mountains ◽  
Life History Characteristics ◽  
Normalised Difference Vegetation Index

Context Timing (mean birthdate) and synchrony (variance around that date) of births can influence survival of young and growth in ungulate populations. Some restored populations of ungulates may not adjust these life-history characteristics to environments of release sites until several years after release, which may influence success of reintroductions. Aims We quantified timing and synchrony of births from 2005 to 2007 in four populations of reintroduced bighorn sheep (Ovis canadensis) occupying two ecoregions (Central Basin and Range and Wasatch and Uinta Mountains) in Utah, USA, to investigate whether bighorns would adjust these life-history characteristics to environmental conditions of the two ecoregions. We also compared timing and synchrony of births for bighorns in their source herd (Antelope Island) with bighorns in an ecologically similar release site (Stansbury Mountains) during 2006 and 2007. Methods We relocated female bighorns to record birthdates of young, and observed groups of collared bighorns to quantify use of elevation by those ungulates. We also calculated the initiation, rate and timing of peak green-up by ecoregion, using the normalised difference vegetation index. Key results We quantified 274 birthdates, and although only separated by 57 km, bighorn populations occupying the Central Basin and Range Mountains gave birth an average of 29 days earlier than did those on the Wasatch and Uinta Mountains, which corresponded with the initiation of vegetation green-up. Additionally, bighorn sheep on the Stansbury Mountains (ecologically similar release site) gave birth at similar times as did bighorns on Antelope Island (source area). Conclusions Populations of bighorn sheep that were reintroduced into adjacent ecoregions adjusted timing of births to environments and green-up of vegetation in restoration areas. Timing and synchrony of births for reintroduced bighorn sheep in an ecologically similar release site were the same as those of their source area. Implications Consideration should be given to the adjustment of timing and synchrony of births when reintroducing bighorns, especially when animals are released into different ecoregions. Also, biologists should select release sites that are ecologically similar to source areas, thereby reducing potential negative effects of animals adjusting timing and synchrony of births to environmental conditions of restoration areas.

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