The Himalayan Orogenic Segment

Fort, Patrick Le

doi:10.1007/978-94-009-2253-2_16

Cited by 49 publications

(13 citation statements)

References 152 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4). While the original relationship between the underlying orthogneiss and the phyllitic schist is not known, orthogneiss units in similar structural positions along the Himalayan front (e.g., Ulleri augen gneiss) have been interpreted as intercalated volcanoclastics (Le Fort, 1975), metasomatized granitic basement (Arita, 1983), or granitic lacco liths (Le Fort, 1989). The contact between the units now is tectonic.…”

Section: Figure 3 Geologic Map Of the Tama Kosi-rolwaling Himalaya mentioning

confidence: 99%

The geology of the Tama Kosi and Rolwaling valley region, East-Central Nepal

Larson

2012

Geosphere

View full text Add to dashboard Cite

The Tama Kosi/Rolwaling area of eastcentral Nepal is underlain by the exhumed mid-crustal core of the Himalaya. The geology of the area consists of Greater Himalayan sequence phyllitic schist, paragneiss, and orthogneiss that generally increase in metamorphic grade from biotite ± garnet assemblages to sillimanite-grade migmatite up structural section. All metamorphic rocks are pervasively deformed and commonly record top-to-the-south sense shear. The top of the Greater Himalayan sequence in the mapped area is marked by an undeformed, pegmatitic leucogranite stock. Relationships in adjacent areas constrain the age of the leucogranite and the deformation structures it crosscuts, including the top-to-thesouth sense deformation, to be older than middle Miocene. The lower portion of the exhumed midcrustal package has been subject to late-stage folding during the formation of the Tama Kosi window, a structural culmination that may refl ect out-of-sequence adjustment of the orogenic wedge. The geology of the mapped area appears similar to that observed in the adjacent, better-studied Everest region.

show abstract

Section: Figure 3 Geologic Map Of the Tama Kosi-rolwaling Himalaya mentioning

confidence: 99%

The geology of the Tama Kosi and Rolwaling valley region, East-Central Nepal

Larson

2012

Geosphere

View full text Add to dashboard Cite

show abstract

“…Chronology of the sediments remained largely unknown because of the absence of either paleontological (no index fossils with narrow time range) or isotopic age (no datable volcanic ashes probably due to remote location of the typical volcanic sources in Afghanistan) data. Further recognition that the Sub-Himalayan basin has an accretionary prism-like structure, characterized by a package of 3 multiple, several to a few tens of kilometers wide, deformed slices bounded by series of thrusts resulting from continuous slightly oblique convergence, revealed its true complexity (Herail et al, 1986;Le Fort, 1989 andMugnier et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Depositional chronology and fabric of Siwalik group sediments in Central Nepal from magnetostratigraphy and magnetic anisotropy

Gautam

Rösler

1999

Journal of Asian Earth Sciences

View full text Add to dashboard Cite

Magnetostratigraphic research, undertaken within the past 15 years in the Siwaliks distributed along 400 km of the Sub-Himalaya in central Nepal, has proved that the sediments possess highly reliable hematite-based primary detrital remanent magnetization suitable to determine depositional chronology. In order to bring out the polarity sequences in a common chronological frame, all available data are newly correlated to the latest global magnetic polarity time scale of Cande and Kent (1995). Chronological data presented are referred in relation to the diverse lithological nomenclature to the formations whose ages are not constrained by isotopic or paleontologic ages. The age of the sections dated by magnetostratigraphy ranges between 14 and <2 Ma. Sediment accumulation rates average to 32-50 cm kyr -1 . Rock-magnetic parameters, e.g. initial susceptibility and isothermal remanent magnetization ratios, allow correlation with an accuracy of up to a few hundred meters among several kilometers thick adjacent sections.Anisotropy of magnetic susceptibility (AMS) data reveal a well-defined fabric contributed by paramagnetic (k = 10 -5 to 3x10 -4 SI) as well as ferromagnetic minerals (k = 3x10 -4 to 10 -2 SI). AMS ellipsoids are mainly oblate along with prolate ones and the degree of anisotropy is mostly low (P"<1.2). The magnetic fabric is of pre-folding origin with tiltcorrected sub-vertical magnetic foliation poles. The magnetic lineations do not show parallelism to the expected paleocurrent directions. Rather, sub-parallelism between the clusters of magnetic lineation and the fold axes/bedding strikes/thrust fronts is observed. A superimposed fabric consisting of a sedimentary-compactional and an overprint induced by mild deformation process is suggested. The latter process was active during and subsequent to the deposition in the compressive tectonic setting of the foreland basin. The magnetic lineations for Tinau Khola and Surai Khola sections cluster around N80W and N88W respectively, whereas N27W trend characterizes the Amiliya-Tui area south of Dang. The peak clusters in lineations are probably orthogonal to the true shortening axes. Their variation along the Sub-Himalaya, together with the fold axes or thrust front trends, may be used for accurate tectonic reconstruction. It is especially important when orthogonality of the latter to the shortening axes may not hold true in the sectors with imbricate fold-and-thrust structures.

show abstract

“…In a comprehensive review of the Himalayan orogen Le Fort (1989) highlights the continuing debate as to the timing of uplift, but favours an earlier (Miocene) initiation in contrast to the rapid uplift since the Early Quaternary advocated by some other workers.…”

Section: Neotectonics and Landformsmentioning

confidence: 93%

Tectonic geomorphology

Summerfield

1991

Progress in Physical Geography: Earth and Environment

View full text Add to dashboard Cite

The past two years have seen a rapidly growing realization amongst both geophysicists and geologists of the importance of relationships between tectonics and landscape development. One focus of interest for geophysicists has been the problem of passive margins, and in particular the inability of many of the initial tectonic models to account for the significant marginal uplands characteristic of many such margins. Of equal significance, however, has been the explicit incorporation of denudation into models of orogen development and an appreciation that spatial variations in denudation may play a key role in controlling the structure of collisional orogenic belts.The growing interest of geologists in geomorphology in general, and tectonic geomorphology in particular, has also arisen from an increasing awareness of the role that the response of the landscape to tectonic processes plays in controlling the infilling of sedimentary basins. In the particular context of terrains experiencing active faulting Leeder et al. (1991) have remarked on the close relationship that exists between tectonics, geomorphology and sedimentology, while Perlmutter and Matthews (1990) have explored the role of tectonics and climate in controlling patterns of erosion and sediment supply. More generally, Leeder (1991) has attempted to link some elementary principles of landscape development to the effects of vertical crustal deformation in order to analyse at the broadest level the factors controlling sediment supply to basins. This new awareness of the geomorphological controls operating on sediment supply is, however, far from universal, as is illustrated by a recent summary of basin sedimentology which pays little attention to morphological features (Allen and Allen, 1990).In this review I will examine some of these issues in more detail as well as briefly considering other important developments in tectonic geomorphology at a wide range of spatial and temporal scales.

show abstract

The Himalayan Orogenic Segment

Cited by 49 publications

References 152 publications

The geology of the Tama Kosi and Rolwaling valley region, East-Central Nepal

The geology of the Tama Kosi and Rolwaling valley region, East-Central Nepal

Depositional chronology and fabric of Siwalik group sediments in Central Nepal from magnetostratigraphy and magnetic anisotropy

Tectonic geomorphology

Contact Info

Product

Resources

About