Lithological and structural controls on river profiles and networks in the northern Sierra Nevada (California, USA)

2019 ◽  
Vol 132 (3-4) ◽  
pp. 655-667 ◽  
Author(s):  
Emmanuel J. Gabet
Keyword(s):  
Sierra Nevada ◽  
Mountain Range ◽  
Late Cenozoic ◽  
Joint Spacing ◽  
Fluvial Systems ◽  
Structural Controls ◽  
Metasedimentary Rocks ◽  
River Profiles ◽  
Lithological Heterogeneity

Abstract In this study, the strong lithological heterogeneity of the northern Sierra Nevada (California, USA) is exploited to elucidate the role of lithology on river profiles and patterns at the mountain-range scale. The analyses indicate that plutonic, metavolcanic, and quartzite bedrock generally host the steepest river reaches, whereas gentle reaches flow across non-quartzite metasedimentary rocks and fault zones. In addition, the largest immobile boulders are often in the steepest reaches, suggesting that wide joint spacing plays a role in creating steep channels, and a positive relationship between boulder size and hillslope angle highlights the coupling of the hillslope and fluvial systems. With respect to river network configurations, dendritic patterns dominate in the plutonic bedrock, with channels aligned down the slope of the range; in contrast, river reaches in the metamorphic belts are mainly longitudinal and parallel to the structural grain. River profiles and patterns in the northern Sierra Nevada, therefore, bear a strong lithological imprint related to differential erosion. These observations indicate that attempts to infer uplift and tilting of the range based on the gradients and orientations of paleochannel remnants should first account for the effect of bedrock erodibility. Indeed, the differences in gradients of Tertiary paleochannel remnants used to argue for late Cenozoic uplift of the range can be wholly explained by differences in lithology.

Evaluating the role of topographic inversion in the formation of the Stanislaus Table Mountains in the Sierra Nevada (California, USA)

2021 ◽  
Author(s):  
Emmanuel Gabet
Keyword(s):  
Sierra Nevada ◽  
Cross Sections ◽  
Late Cenozoic ◽  
River Watershed ◽  
Bedrock Topography ◽  
Volcanic Deposit ◽  
Surrounding Landscape ◽  
Topographic Inversion ◽  
Table Mountains

The Table Mountains, a flat-topped series of ridges capped by a 10.4 Ma latite flow in the Stanislaus River watershed, are considered to be evidence for late Cenozoic uplift-driven landscape rejuvenation in the northern Sierra Nevada range (California, USA). The commonly accepted theory for the formation of these mesas posits that the latite flowed and cooled within a bedrock paleovalley and, since then, the surrounding landscape has eroded away, leaving behind the volcanic deposit as a ridge. Although this theory is accepted by many, it has not been thoroughly tested. In this study, I examine a series of geological cross-sections extracted along the length of the latite deposit to determine whether the evidence supports the existence of bedrock valley walls on both sides of the 10.4 Ma flow. I find that the presence of older Cenozoic deposits adjacent to the latite flow precludes the possibility that the flow would have been constrained within a bedrock valley. Moreover, the cross-section from an 1865 report that has been offered as evidence of topographic inversion (and subsequently reproduced in numerous publications) does not accurately represent the topography at that site. I conclude that there is no evidence that the bedrock topography has been inverted and that instead, the latite flowed within a channel cut into underlying Cenozoic deposits, which have since mostly eroded away. This study, therefore, refutes the hypothesis that the Stanislaus River watershed was rejuvenated in the late Cenozoic and challenges the claim for recent significant uplift of the region.

Minimal net incision of the northern Sierra Nevada (California, USA) since the Eocene–early Oligocene

Geology ◽  
2020 ◽  
Vol 48 (10) ◽  
pp. 1023-1027
Author(s):  
Emmanuel J. Gabet ◽  
Daniel P. Miggins
Keyword(s):  
Sierra Nevada ◽  
North American ◽  
Past Century ◽  
Mountain Range ◽  
Late Cenozoic ◽  
North American Cordillera ◽  
The Past ◽  
The North ◽  
Early Oligocene ◽  
Northern Half

Abstract Significant late Cenozoic uplift (>1000 m) of the northern half of the Sierra Nevada (California, USA), a mountain range in the North American Cordillera, has been a dominant paradigm over the past century. This paradigm has been supported by evidence suggesting that in response to this recent uplift, the range’s deep canyons were incised in the past 3–4 m.y. However, paleochannel elevations compiled from a mining report and geological maps demonstrate that while some modern rivers have incised 560 m below their Eocene–early Oligocene riverbeds, incision by others has been <300 m. For example, Eocene–early Oligocene fluvial gravels can be found just 161 m above the modern channel deep within the canyon of the South Fork American River. We conclude that the initiation of late Cenozoic incision was due to a resumption of a period of downcutting that was interrupted in the Eocene when the rivers were buried by fluvial sediment and by later volcanic deposits. This interpretation challenges the hypothesis that recent uplift was responsible for deep canyon incision. Correctly identifying the causes of recent incision in the northern Sierra Nevada has important implications for understanding the geological history of the North American Cordillera because the range is hypothesized to have been the western ramp of the Nevadaplano.

scholarly journals Fluvial Geomorphology and River Management

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1608
Author(s):  
Salvatore Ivo Giano
Keyword(s):  
Human Activities ◽  
River Restoration ◽  
Fluvial Geomorphology ◽  
Landscape Evolution ◽  
River Management ◽  
Special Issue ◽  
Fluvial Systems ◽  
The Impact

This Special Issue deals with the role of fluvial geomorphology in landscape evolution and the impact of human activities on fluvial systems, which require river restoration and management [...]

scholarly journals Formation Patterns of Mediterranean High-Mountain Water-Bodies in Sierra-Nevada, SE Spain

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 438
Author(s):  
Jose Luis Diaz-Hernandez ◽  
Antonio Jose Herrera-Martinez
Keyword(s):  
Sierra Nevada ◽  
Unknown Origin ◽  
Slope Instability ◽  
Water Bodies ◽  
High Mountain ◽  
Mountain Areas ◽  
Glacial Processes ◽  
The Mediterranean ◽  
Water Volumes

At present, there is a lack of detailed understanding on how the factors converging on water variables from mountain areas modify the quantity and quality of their watercourses, which are features determining these areas’ hydrological contribution to downstream regions. In order to remedy this situation to some extent, we studied the water-bodies of the western sector of the Sierra Nevada massif (Spain). Since thaw is a necessary but not sufficient contributor to the formation of these fragile water-bodies, we carried out field visits to identify their number, size and spatial distribution as well as their different modelling processes. The best-defined water-bodies were the result of glacial processes, such as overdeepening and moraine dams. These water-bodies are the highest in the massif (2918 m mean altitude), the largest and the deepest, making up 72% of the total. Another group is formed by hillside instability phenomena, which are very dynamic and are related to a variety of processes. The resulting water-bodies are irregular and located at lower altitudes (2842 m mean altitude), representing 25% of the total. The third group is the smallest (3%), with one subgroup formed by anthropic causes and another formed from unknown origin. It has recently been found that the Mediterranean and Atlantic watersheds of this massif are somewhat paradoxical in behaviour, since, despite its higher xericity, the Mediterranean watershed generally has higher water contents than the Atlantic. The overall cause of these discrepancies between watersheds is not connected to their formation processes. However, we found that the classification of water volumes by the manners of formation of their water-bodies is not coherent with the associated green fringes because of the anomalous behaviour of the water-bodies formed by moraine dams. This discrepancy is largely due to the passive role of the water retained in this type of water-body as it depends on the characteristics of its hollows. The water-bodies of Sierra Nevada close to the peak line (2918 m mean altitude) are therefore highly dependent on the glacial processes that created the hollows in which they are located. Slope instability created water-bodies mainly located at lower altitudes (2842 m mean altitude), representing tectonic weak zones or accumulation of debris, which are influenced by intense slope dynamics. These water-bodies are therefore more fragile, and their existence is probably more short-lived than that of bodies created under glacial conditions.

scholarly journals Role of glaciers in watershed hydrology: a preliminary study of a "Himalayan catchment"

2010 ◽  
Vol 4 (1) ◽  
pp. 115-128 ◽  
Author(s):  
R. J. Thayyen ◽  
J. T. Gergan
Keyword(s):  
Mass Balance ◽  
River Flow ◽  
Initial Increase ◽  
Glacier Mass Balance ◽  
Mountain Range ◽  
Humid Climate ◽  
Flow Response ◽  
Sustainable Water Resources Management ◽  
South West Monsoon

Abstract. A large number of Himalayan glacier catchments are under the influence of humid climate with snowfall in winter (November–April) and south-west monsoon in summer (June–September) dominating the regional hydrology. Such catchments are defined as "Himalayan catchment", where the glacier meltwater contributes to the river flow during the period of annual high flows produced by the monsoon. The winter snow dominated Alpine catchments of the Kashmir and Karakoram region and cold-arid regions of the Ladakh mountain range are the other major glacio-hydrological regimes identified in the region. Factors influencing the river flow variations in a "Himalayan catchment" were studied in a micro-scale glacier catchment in the Garhwal Himalaya, covering an area of 77.8 km2. Three hydrometric stations were established at different altitudes along the Din Gad stream and discharge was monitored during the summer ablation period from 1998 to 2004, with an exception in 2002. These data have been analysed along with winter/summer precipitation, temperature and mass balance data of the Dokriani glacier to study the role of glacier and precipitation in determining runoff variations along the stream continuum from the glacier snout to 2360 m a.s.l. The study shows that the inter-annual runoff variation in a "Himalayan catchment" is linked with precipitation rather than mass balance changes of the glacier. This study also indicates that the warming induced an initial increase of glacier runoff and subsequent decline as suggested by the IPCC (2007) is restricted to the glacier degradation-derived component in a precipitation dominant Himalayan catchment and cannot be translated as river flow response. The preliminary assessment suggests that the "Himalayan catchment" could experience higher river flows and positive glacier mass balance regime together in association with strong monsoon. The important role of glaciers in this precipitation dominant system is to augment stream runoff during the years of low summer discharge. This paper intends to highlight the importance of creating credible knowledge on the Himalayan cryospheric processes to develop a more representative global view on river flow response to cryospheric changes and locally sustainable water resources management strategies.

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