The Bruneau-Jarbidge eruptive center, southwestern Idaho

1989 ◽  
pp. 78-85
Author(s):  
Bill Bonnichsen
Keyword(s):  
Eruptive Center

Linking exhumation, paleo-relief, and rift formation to magmatic processes in the Western Snake River Plain, Idaho

2021 ◽  
Author(s):  
Jessica Stanley ◽  
Kelsey Wetzel
Keyword(s):  
Snake River Plain ◽  
Large Igneous Province ◽  
Negative Slope ◽  
Snake River ◽  
Eruptive Center ◽  
Base Level ◽  
Structural Style ◽  
Columbia River Basalt ◽  
Slab Rollback ◽  
River Plain

<p>Southwest Idaho has experienced substantial topographic changes over the Cenozoic that are reflections of complex tectonic and mantle processes. The western Snake River Plain (WSRP) in southwest Idaho has been characterized as an intracontinental rift basin but differs markedly in topography and style from other western Cordilleran extensional structures. It also differs in orientation and structural style from the down warped lava plain of the eastern Snake River Plain that follows the path of the Yellowstone hotspot (YHS). Potential magmatic drivers for WSRP formation include the ~12-10 Ma Bruneau-Jarbidge eruptive center of the YHS or the ~17-16 Ma Columbia River Basalt (CRB) large igneous province. To better constrain the timing and style of rifting in the region we sampled granitoid bedrock from Cretaceous and Eocene-aged plutons from the flanks of the WSRP to detail their exhumation history with apatite (U-Th)/He (AHe) thermochronometry. We present new AHe dates from seventeen samples, with cooling dates ranging range from 7 Ma to 55 Ma. The majority of cooling dates for the Cretaceous plutons are Eocene, and the Eocene intrusions yield Miocene dates. The AHe dates provide thermochronological evidence of rapid cooling and exhumation of the Idaho batholith during the Eocene. This supports the presence a high relief landscape in Idaho associated with regional uplift due to Farallon slab rollback and Challis magmatism. We also find evidence for a post-Eocene decrease in relief, seen in the negative slope on date-elevation relationships in the southwest flank of the WSRP. Our AHe dates indicate limited exhumation on the flanks of the WSRP during Miocene rift formation. We interpret this to be evidence of extension dominated by magmatic intrusions and intrabasin faults rather than basin-bounding faults. Miocene AHe dates show rapid exhumation along the Middle Fork Boise River that had begun by ~17 Ma. We take this to indicate focused incision along the river due to base level fall in the WSRP and the timing suggests that CRB activity was responsible for initiation of WSRP formation</p>

Vegetation cover at the Maguntan mud volcano (Sakhalin Island, Russia): species composition and spatial distribution

2015 ◽  
Vol 45 (1) ◽  
pp. 125-134 ◽  
Author(s):  
Kirill Korznikov
Keyword(s):  
Spatial Distribution ◽  
Plant Communities ◽  
Vegetation Cover ◽  
Plant Cover ◽  
Stress Gradient ◽  
Mud Volcano ◽  
Grass Species ◽  
Eruptive Center ◽  
Floristic Richness ◽  
Local Endemic

Mud volcano vegetation is not well-studied even in comparison with that of geothermal areas. Mud volcanoes provide opportunities to study the formation of the spatial and species structure of vegetation cover in distinct conditions, showing the trends in vegetation succession. The mud fields of the Maguntan mud volcano (Sakhalin, Russia) are cool, not warm, and their mud fluids have high salinity and alkalinity. In the 20th century some local endemic taxa were found at this place: Artemisia limosa, Gentianella sugawarae, Primula sachalinensis and Deschampsia tzvelevii. I identified nine plant communities and analyzed floristic richness, vegetation cover and endemism rate using data from 185 1 m × 1 m quadrats. The salinity decreases with distance from the volcano's main eruptive center. The total plant cover, number of plant species, and floristic richness increase with the distance from the volcano's center. Endemic taxa including the local endemic grass species Deschampsia tzvelevii are located in young mud substrates. Detrended correspondence analysis showed that the plant communities are arranged along a stress gradient. The spatial distribution of plant communities may be interpreted via succession dynamics.

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