Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India
The Spiti region, renowned as the Museum of Indian Geology, is a world-famous sedimentary succession containing well-exposed sequences from Neoproterozoic to Cretaceous age. In this study, Triassic siliciclastic sedimentary rocks of the Lilang Supergroup were chosen to understand weathering history,...
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Elsevier
2023-06-01
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| Series: | Journal of Asian Earth Sciences: X |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2590056023000191 |
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| author | Javid A. Ganai Shaik A. Rashid Abdul Samad Siddiqui Nurul Absar Heena Ghulam Jeelani |
| author_facet | Javid A. Ganai Shaik A. Rashid Abdul Samad Siddiqui Nurul Absar Heena Ghulam Jeelani |
| author_sort | Javid A. Ganai |
| collection | DOAJ |
| description | The Spiti region, renowned as the Museum of Indian Geology, is a world-famous sedimentary succession containing well-exposed sequences from Neoproterozoic to Cretaceous age. In this study, Triassic siliciclastic sedimentary rocks of the Lilang Supergroup were chosen to understand weathering history, provenance, paleoclimate, and depositional conditions using a geochemical and isotopic approach. Triassic shales show more or less similar compositions with substantial enrichment in CaO compared to PAAS (Post Archean shales from Australia), which may be attributed to the association with limestones in the region. However, the sandstones display significant depletion in the trace element concentrations signifying the effect of quartz dilution. The relative depletion of mobile elements (Rb, Ba) as against immobile elements (Zr, Nb, Hf) can be noticed in the trace element spider diagram of the shales. The Triassic sedimentary rocks are characterized by enriched LREE and depleted HREE patterns with pronounced negative Eu anomalies. The Chemical Index of Alteration (CIA; 56–86) indicates low to intense chemical weathering in the source area. The unusual decrease in CIA and other weathering indices in the stratigraphically up section is attributed to changes in climate and environmental conditions during the deposition of sediments in the Triassic period. Detangling the signatures is crucial to understanding the mass extinction crisis, particularly the role of anoxia in these events. Triassic black shales represent suboxic to anoxic depositional conditions in the redox-sensitive elemental binary diagrams. The carbon isotope data of the present study is very well supported by the Total Organic Carbon (TOC), which infers that the oceanic biological system tried to recover from the depletion of biological life. The εNd and 87Sr/86Sr systematics record a shift in source terrains from the Early to Late Triassic period. The Early Triassic samples show much older depleted mantle model ages (TDM = 1.94–1.98 Ga) compared to Late Triassic sediments (TDM = 1.76–1.91 Ga). Similar interpretations can be drawn from Th/Sc ratios (from ∼ 6 to ∼ 0.05) and (La/Yb) N ratios (from ∼ 32 to ∼ 5), which record an increase in these ratios from Early Triassic to Late Triassic formations of the Spiti sedimentary rocks. Overall, trace elemental ratios and radiogenic isotopic signatures of the Triassic rocks of the Spiti region point towards Pan African granitic origin with minor impressions from the juvenile mafic-rich sources, such as Panjal Traps, the African craton, and Arabian-Nubian shield. |
| first_indexed | 2024-03-13T03:43:27Z |
| format | Article |
| id | doaj.art-46a3cfee594e4bd8b5d8d748128fd7dc |
| institution | Directory Open Access Journal |
| issn | 2590-0560 |
| language | English |
| last_indexed | 2024-03-13T03:43:27Z |
| publishDate | 2023-06-01 |
| publisher | Elsevier |
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| series | Journal of Asian Earth Sciences: X |
| spelling | doaj.art-46a3cfee594e4bd8b5d8d748128fd7dc2023-06-23T04:43:57ZengElsevierJournal of Asian Earth Sciences: X2590-05602023-06-019100154Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, IndiaJavid A. Ganai0Shaik A. Rashid1Abdul Samad Siddiqui2Nurul Absar3 Heena4Ghulam Jeelani5Department of Earth Sciences, Kashmir University, Srinagar 190006, India; Corresponding author.Department of Geology, Aligarh Muslim University, Aligarh 202001, IndiaGeological Survey of India, Western Region, Gandhinagar 382010, IndiaDepartment of Earth Sciences, Pondicherry University, Puducherry 605014, IndiaDepartment of Geology, Aligarh Muslim University, Aligarh 202001, IndiaDepartment of Earth Sciences, Kashmir University, Srinagar 190006, IndiaThe Spiti region, renowned as the Museum of Indian Geology, is a world-famous sedimentary succession containing well-exposed sequences from Neoproterozoic to Cretaceous age. In this study, Triassic siliciclastic sedimentary rocks of the Lilang Supergroup were chosen to understand weathering history, provenance, paleoclimate, and depositional conditions using a geochemical and isotopic approach. Triassic shales show more or less similar compositions with substantial enrichment in CaO compared to PAAS (Post Archean shales from Australia), which may be attributed to the association with limestones in the region. However, the sandstones display significant depletion in the trace element concentrations signifying the effect of quartz dilution. The relative depletion of mobile elements (Rb, Ba) as against immobile elements (Zr, Nb, Hf) can be noticed in the trace element spider diagram of the shales. The Triassic sedimentary rocks are characterized by enriched LREE and depleted HREE patterns with pronounced negative Eu anomalies. The Chemical Index of Alteration (CIA; 56–86) indicates low to intense chemical weathering in the source area. The unusual decrease in CIA and other weathering indices in the stratigraphically up section is attributed to changes in climate and environmental conditions during the deposition of sediments in the Triassic period. Detangling the signatures is crucial to understanding the mass extinction crisis, particularly the role of anoxia in these events. Triassic black shales represent suboxic to anoxic depositional conditions in the redox-sensitive elemental binary diagrams. The carbon isotope data of the present study is very well supported by the Total Organic Carbon (TOC), which infers that the oceanic biological system tried to recover from the depletion of biological life. The εNd and 87Sr/86Sr systematics record a shift in source terrains from the Early to Late Triassic period. The Early Triassic samples show much older depleted mantle model ages (TDM = 1.94–1.98 Ga) compared to Late Triassic sediments (TDM = 1.76–1.91 Ga). Similar interpretations can be drawn from Th/Sc ratios (from ∼ 6 to ∼ 0.05) and (La/Yb) N ratios (from ∼ 32 to ∼ 5), which record an increase in these ratios from Early Triassic to Late Triassic formations of the Spiti sedimentary rocks. Overall, trace elemental ratios and radiogenic isotopic signatures of the Triassic rocks of the Spiti region point towards Pan African granitic origin with minor impressions from the juvenile mafic-rich sources, such as Panjal Traps, the African craton, and Arabian-Nubian shield.http://www.sciencedirect.com/science/article/pii/S2590056023000191Spiti regionTethys HimalayaBlack shalesGeochemistryIsotopesProvenance |
| spellingShingle | Javid A. Ganai Shaik A. Rashid Abdul Samad Siddiqui Nurul Absar Heena Ghulam Jeelani Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India Journal of Asian Earth Sciences: X Spiti region Tethys Himalaya Black shales Geochemistry Isotopes Provenance |
| title | Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India |
| title_full | Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India |
| title_fullStr | Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India |
| title_full_unstemmed | Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India |
| title_short | Understanding the provenance and depositional conditions of Triassic sedimentary rocks from the Spiti region, Tethys Himalaya, India |
| title_sort | understanding the provenance and depositional conditions of triassic sedimentary rocks from the spiti region tethys himalaya india |
| topic | Spiti region Tethys Himalaya Black shales Geochemistry Isotopes Provenance |
| url | http://www.sciencedirect.com/science/article/pii/S2590056023000191 |
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