担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Wrinkle ridges (WR) are well-established paleo-stress indicators providing information on the compressional history and thermal evolution of Mars. Therefore, constraining their timing of formation on a global scale could yield better insight into the tectonic history, evolution of the mantle, and the paleoclimate of the planet. Here, we have updated the existing global map of the Martian WRs (up to a latitude of 70o on either hemisphere) using high-resolution Context (CTX) Camera images from twenty-seven different regions and inferred their ages using the Buffer Crater Counting (BCC) technique. The BCC technique enables us to conduct age estimation even when WRs propagated through more than one geological unit, or even the accountable compressional stress is younger than the underlying geologic unit, giving an additional advantage over the conventional relative age estimation technique. Globally, we have found that the ages of the WRs are almost entirely of the Early Hesperian (3.66–3.4 Ga) phenomenon, with exceptions from the Sinai Planum (~ 3.14 Ga; Late Hesperian) or dichotomy perpendicular ridges from the Amenthes Planum (~2.52 Ga; Amazonian) which possibly produced due to the horizontal forces that emerged due to isostatic adjustments. We have identified at least five distinct phases (~3.66, 3.62, 3.59, 3.48, and 3.14 Ga) of compressional deformations, related to the crustal growth in response to isostatic adjustments and flexural loading from the Noachian/Hesperian boundary period to the Late Hesperian period in and around the Tharsis region. In the eastern hemisphere, we have observed that the WR formation-stresses are global (peak global contraction ~3.59–3.55 Ga; responsible for the formation of WRs within southern highlands, parts of northern lowlands) to regional (around Syrtis Major and Malea Planum) in scale. Additionally, the estimated WR-ages indicate multiple phases of volcanic activity (~3.7, 3.54, and 3.40 Ga) eventuated at several provinces of the planet. Therefore, we conclude from the observation of WR-formation ages that the Martian mantle was vastly active during the Noachian/Hesperian boundary and the intensity of the mantle activity decreased through time, giving rise to multiple pulses of regional volcano-tectonic events, as a part of thermal evolution over the Hesperian period.

DOI： 10.1016/j.icarus.2021.114625

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Current Science Association  

DOI： 10.18520/cs/v121/i7/906-911

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Extensional and compressional structures are globally abundant on Mars. Distribution of these structures and their ages constrain the crustal stress state and tectonic evolution of the planet. Here in this paper, we report on our investigation over the distribution of the tectonic structures and timings of the associated stress fields from the Noachis-Sabaea region. Thereafter, we hypothesize possible origins in relation to the internal/external processes through detailed morphostructural mapping. In doing so, we have extracted the absolute model ages of these linear tectonic structures using crater size-frequency distribution measurements, buffered crater counting in particular. The estimated ages indicate that the tectonic structures are younger than the mega impacts events (especially Hellas) and instead they reveal two dominant phases of interior dynamics prevailing on the southern highlands, firstly the extensional phase terminating around 3.8 Ga forming grabens and then compressional phase around 3.5–3.6 Ga producing wrinkle ridges and lobate scarps. These derived absolute model ages of the grabens exhibit the age ca. 100 Ma younger than the previously documented end of the global extensional phase. The following compressional activity corresponds to the peak of global contraction period in Early Hesperian. Therefore, we conclude that the planet wide heat loss mechanism, involving crustal stretching coupled with gravitationally driven relaxation (i.e., lithospheric mobility) resulted in the extensional structures around Late Noachian (around 3.8 Ga). Lately cooling related global contraction generated compressional stress ensuing shortening of the upper crust of the southern highlands at the Early Hesperian period (around 3.5–3.6 Ga).

DOI： 10.1016/j.gsf.2018.05.016

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Southern highlands of Mars have experienced regional to global scale deformations in the history of its evolution. Deformational structures originated from impact-induced stresses and later viscous relaxation of the impact basin to cooling related global contraction. Here in this study, we investigated an Early Hesperian (Eo-Archean / Paleo-Archean equivalent to the Earth) aged lobate scarp i.e., surface signature of thrust fault, possibly originated because of global contraction. We used ‘offset crater perimeter’ measurement technique using high-resolution data (both image and DTM) to execute most precise estimation of fault plane slope and length–displacement relationship. The derived range of fault plane slope is much narrower (21°–29°) than the previously cited 20° to 35° range. Displacement–length ratio (4.51 × 10−3) is also unique and lower than the previously evaluated values of lobate scarps from other region (mainly from dichotomy boundary) of Mars. The newly derived results from the morphometric analysis are due the differential stress pattern and the distinct basement rock rheology. Our results highlight the need for more high-resolution estimation of lobate scarps from several regions with the methodology employed in this study to better understand the global Martian early tectonic scenario.

DOI： 10.1016/j.jsg.2018.04.018

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）  

The Noachis-Sabaea region in the southern highlands preserves some of the oldest Martian crust. It records deformation by both endogenic and exogenic processes. This deformation includes giant impacts and their impact stresses, which could have resulted in both the reactivation and modification of pre-impact tectonic structures, in addition to impactgenerated tectonic structures. There are also widespread extensional and compressional tectonic structures, which were formed due to endogenic processes. We have produced the first detailed morphostructural map of the Noachis-Sabaea region, which details the characteristics and spatial arrangements of structures in the region, forms the basis for making inferences about Noachian-Hesperian crustal activity, and provides information for further studies regarding the reconstruction of the evolutional history of the region.

DOI： 10.1080/17445647.2017.1379913

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Partial melting in the middle to lower crustal level produces melts of granitic composition during orogeny. Thrusts play a vital role in their exhumation after consolidation of these granitic melts. In this paper we focus on one such granite along the eastern margin of the Delhi Fold Belt (DFB) rocks near Srinagar, Rajasthan, India. This is the first report of granite within the area and holds a key stratigraphic position in the entire rock package. The said granite is found to be intrusive to the DFB metasediments as well as their basement popularly known as the Banded Gneissic Complex (BGC). We disentangle the deformation fabrics seen within the granite and associated DFB metasediments, suggesting that subsequent to emplacement and consolidation, the granite has co-folded along with the country rocks. Three deformational events could be identified within the DFB metasediments namely, D1D, D2D and D3D. The peak metamorphism was achieved in the D1D event. The granite magma is generated and emplaced late syn-kinematic to D1D and thereafter is deformed by D2D and D3D producing D1G and D2G structural fabrics. These compressive deformations resulted in the collapse of the basin; the combined package of DFB rocks and the granite was thrusted eastwards over the basement rocks. The tectonic transport direction during thrusting is suggested eastwards from our structural analysis. Transverse faults developed perpendicular to the length of the granite have led to partitioning of the strain thereby showing a heterogeneity in the development of fabric within it.

DOI： 10.1007/s12040-014-0461-9

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開催年月日： 2024年4月26日 - 2024年4月30日

記述言語：英語   会議種別：口頭発表（一般）  

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開催年月日： 2024年4月26日 - 2024年4月30日

記述言語：英語   会議種別：口頭発表（一般）  

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開催年月日： 2024年4月26日 - 2024年4月30日

記述言語：日本語   会議種別：ポスター発表  

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開催年月日： 2024年4月26日 - 2024年4月30日

記述言語：日本語   会議種別：口頭発表（一般）  

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開催年月日： 2024年4月26日 - 2024年4月30日

記述言語：日本語   会議種別：ポスター発表  

researchmap

開催年月日： 2024年4月26日 - 2024年4月30日

記述言語：日本語   会議種別：口頭発表（一般）  

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開催年月日： 2024年3月11日 - 2024年3月15日

記述言語：英語   会議種別：ポスター発表  

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開催年月日： 2024年3月11日 - 2024年3月15日

記述言語：英語   会議種別：ポスター発表  

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記述言語：日本語   会議種別：口頭発表（一般）  

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記述言語：日本語   会議種別：口頭発表（一般）  

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