Geomorphological processes and landforms of glacier forelands in the upper Aktru River basin (Gornyi Altai), Russia: evidence for rapid recent retreat and paraglacial adjustment

Abstract The drainages of the Iguaçu River basin, as well as the main channel of the river, have peculiar characteristics resulting from geomorphological processes in this area, including the formation of the Iguaçu River Falls. This slope in the lower portion of the basin is a biogeographical barrier to many organisms. In this study was inventoried the fish fauna of streams of the lower Iguaçu River basin, evaluating possible differences in the species composition upstream and downstream of this biogeographical barrier. Sampling were conducted between 2004 and 2013, in five streams, three upstream and two downstream of the Iguaçu River Falls, using electrofishing. The nMDS analysis was run to investigate possible groupings of similar fauna between the streams sampled. The scores of this test were tested as to the significance of groupings with the Hotelling T2 test. The indicator value method (IndVal) was used to detect the distribution of species among the groups of the streams upstream and downstream of the Iguaçu River Falls. We collected 18,908 individuals of six orders, 11 families, and 40 species. Siluriformes and Characiformes had the highest species richness; Cyprinodontiformes presented the highest abundance. Considering the species recorded, 21 are considered natives to the Iguaçu River basin, including 15 endemic, wich were found only in streams upstream of the falls. Additional 18 species were verified only in the streams downstream of such barrier. Four species were common to both stretches. The axis 1 of the nMDS separated two groups: streams upstream (S1, S2 and S3) and streams downstream of the Iguaçu River Falls (S4 and S5). The indicator species analysis also indicated a distinction between the groups of streams, that were significantly different (Hotelling's T2 = 234.36, p ˂ 0.0001). The number of endemic species in the streams upstream of the Falls (15 spp.) evidences a significant effect of isolation promoted by the Iguaçu River Falls, and confirms the role of this barrier in the vicariant processes and endemism typical of this basin. These results emphasize the importance of conserving these ecosystems, once the extinction of species in this region means the irreversible loss of them.

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The Use of Potsherds for Interpreting Alluvial Deposits: A Case Study in the Adige River Basin (Italy)

MRS Proceedings ◽

10.1557/proc-185-561 ◽

1990 ◽

Vol 185 ◽

Cited By ~ 1

Author(s):

C. Balista ◽

S.T. Levi ◽

A. Vanzetti ◽

M. Vidale

Keyword(s):

River Basin ◽

Analytical Framework ◽

Formation Processes ◽

Alluvial Deposits ◽

Fluvial Erosion ◽

Stratigraphic Analysis ◽

Geomorphological Processes

AbstractThe paper discusses the use of a small assemblage of potsherds as evidence of fluvial erosion and indicators of microstratigraphical and geomorphological processes. The potsherds, sandwiched between 2 alluvial deposits, provide dating criteria for the two stratigraphic units, very important for understanding the geomorphology of the whole region. By integrating evidence of negative interfaces on potsherds by fluvial erosion and sedimentological evidence, it is possible to reconstruct the local stratigraphic formation processes. Furthermore, the paper discusses some theoretical implications of this case study for stratigraphic analysis. Negative interfaces produced by erosion on sediments and ceramics are considered in the same analytical framework; in both cases, they represent cumulative units preserving the record of complex stratigraphic processes. Far from being simple limits marking gaps in sedimentary deposition, erosive interfaces are very particular types of strata to be recorded and studied with geoarchaeological methods and with the same detail of traditional sedimentary units.

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