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Abstract <p>Identification of various lava flow morphotypes within thick mafic lava sequences often gives meaningful insights regarding the transportation and style of emplacement in planetary volcanism. The present work reports and describes in detail the rubbly pahoehoe lava flows, one of the transitional morphotypes between pahoehoe- and a’a-type end members, from the Lad-Ryngud&#xa0;– Laitiam road section from Sylhet Traps, northeastern India. Here, the pahoehoe flow lobes with coherent, gently undulating glassy bases are topped by disrupted crustal zones with clasts of various sizes and shapes. These crustal rubbly or brecciated zones are composed of clasts of earlier solidified lava welded together by the lava itself that make up the lobe interior and are also found to be engulfed within overriding lobes. These rubbly pahoehoe lobes are often found to be emplaced over dipping paleo surfaces without any preferred direction. The frequent presence of the rubbly pahoehoe ones in the studied section is inferred to be controlled by factors like pulsating nature lava effusion, variable viscosities, emplacement over undulating paleo-surfaces, and change of strain rates.</p> Research highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>In the present work, rubbly pahoehoe lobes are observed within a compound pahoehoe lava flow as transitional forms. Rubbles have formed due to several process like, lava flows are being broken and auto-brecciated in semisolid stage and engulfed by the molten lava. Earlier emplaced lava flows comprised of relatively different basaltic material are irregularly broken as Flow Top Breccias and have got entrenched within subsequent overriding lava flows. Inclined paleo-surfaces for emplacement of lava flows have also played a major in development of rubbly lobes within the compound pahoehoe lava flow.</p> </ItemContent> </UnorderedList></p>

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Variants of rubbly pahoehoe flows from Sylhet Traps, Shillong Plateau, northeast India: Implications on lava emplacement and evolution of the volcanic system

  • 期刊论文

  • 发表日期：

    2025年2月21日

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  • Jayanta Kumar Naik,
  • Bibhas Sen,
  • Tapos Kumar Goswami,
  • Rashmi Rekha Naik,
  • Ranjan Kumar Sarmah

摘要

Abstract

Identification of various lava flow morphotypes within thick mafic lava sequences often gives meaningful insights regarding the transportation and style of emplacement in planetary volcanism. The present work reports and describes in detail the rubbly pahoehoe lava flows, one of the transitional morphotypes between pahoehoe- and a’a-type end members, from the Lad-Ryngud – Laitiam road section from Sylhet Traps, northeastern India. Here, the pahoehoe flow lobes with coherent, gently undulating glassy bases are topped by disrupted crustal zones with clasts of various sizes and shapes. These crustal rubbly or brecciated zones are composed of clasts of earlier solidified lava welded together by the lava itself that make up the lobe interior and are also found to be engulfed within overriding lobes. These rubbly pahoehoe lobes are often found to be emplaced over dipping paleo surfaces without any preferred direction. The frequent presence of the rubbly pahoehoe ones in the studied section is inferred to be controlled by factors like pulsating nature lava effusion, variable viscosities, emplacement over undulating paleo-surfaces, and change of strain rates.

Research highlights

In the present work, rubbly pahoehoe lobes are observed within a compound pahoehoe lava flow as transitional forms. Rubbles have formed due to several process like, lava flows are being broken and auto-brecciated in semisolid stage and engulfed by the molten lava. Earlier emplaced lava flows comprised of relatively different basaltic material are irregularly broken as Flow Top Breccias and have got entrenched within subsequent overriding lava flows. Inclined paleo-surfaces for emplacement of lava flows have also played a major in development of rubbly lobes within the compound pahoehoe lava flow.