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ichnofabric analysis of bathyal chalks:the Miocene Inglis Formation of the Andaman and Nicobar Islands,India

Journal of Palaeogeography 2021年第4期10卷 494-508页

作者： Bhawanisingh G.Desai School of Petroleum Technology Pandit Deendayal Energy UniversityGandhinagarGujaratIndia

In the Bay of Bengal,the Andaman and Nicobar Islands represent part of the Burma-Sunda-Java subduction *** Islands are composed of sediments ranging in age from Jurassic to Recent,represented by ophiolites,flysch sediments,along with deep marine sediments scraped off from the subducting *** stratigraphic succession that overlies meta-sedimentary and ophiolite suites consists of turbidite and non-turbidite sequences,along with thick-bedded nannofossil *** present study describes ichnofabrics of chalks from the Inglis Formation(Early to Middle Miocene).These chalks are highly to moderately bioturbated and comprise several levels of ferruginised layers as weak discontinuity *** studied section shows the recurring occurrence of ichnotaxa belonging to Asterosoma,Chondrites,Cladichnus,Ophiomorpha,Palaeophycus,Planolites,Taenidium,Thalassinoides,and *** are represented by Bioturbation indices varying between BI-2 to BI-5,represented by(a)light coloured trace fossils in dark sediment(LID ichnofabric)and(b)dark coloured trace fossils in light sediment(DIL ichnofabric).ichnofabric analysis suggests multiple colonization,complex tiering,and multilayer *** LID ichnofabric exposed at Kalapathar reveals three tiers,a diverse shallow tier and a moderately low diverse middle and deep *** the Lacam Point Section,in contrast,the LID ichnofabric is represented by condensation of the tiers and the absence of shallow *** DIL ichnofabric at the Kalapathar Section seems to be more expanded and is represented by four tiers with extensive *** analysis supports deposition of the chalk sediments in a lower bathyal paleoenvironment and suggests that organic matter,pore water,and bottom-water oxygenation were the main controlling ***,the ichnofabric analysis of the EarlyMiddle Miocene Inglis Formation gives first-hand information regarding the poorly known chalk facies of the Andaman and Nicobar Islan

关键词： ichnofabric Nannofossil ooze Chalk Bathyal Bay of Bengal Miocene

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Taenidium barretti ichnofabric and rainfall seasonality:Insights into dryland suites of Scoyenia ichnofacies

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Journal of Palaeogeography 2023年第1期12卷 28-49页

作者： Diego Luciano Nascimento Renata Guimaraes Netto Alessandro Batezelli Francisco Sergio Bernardes Ladeira Daniel Sedorko ICHNOS Research Group Geology Graduate ProgramUnisinos UniversityAv.Unisinos95010 Sao LeopoldoRS93022-750Brazil Campinas State University Geology and Natural Resources DepartmentZeferino Vaz University CityBarao GeraldoCampinasSP13083-970Brazil Laboratory of Pedology(LABPED) Department of GeographyGeosciences InstituteGeosciencesState University of CampinasCampinasSP13083-855Brazil Museu Nacional Departamento de Geologia e PaleontologiaUniversidade Federal do Rio de Janeiro.Horto BotanicoParque Quinta da Boa VistaR.Gen.Herculano Gomes1340Sao CristovaoRio de JaneiroRJ20940-040Brazil

The present work analyzes the monotypic Taenidium barretti ichnofabric developed in abandoned channels and floodplains to understand its paleoecological significance in highly seasonal fluvial *** data come from the Cretaceous paleosols of the Marília Formation(Bauru Basin,SE Brazil),in which the *** ichnofabric and rhizoliths represent the biotic *** larvae are considered to be the most likely *** tracemakers in these *** intensity and recurrence of bioturbation suggest that the windows of opportunity for beetle population growth were very short and controlled by the progressive substrate desiccation after flood *** characteristics of the trace fossil assemblage suggest soil colonization by r-strategic organisms triggered by flooding events that provided the resource inputs necessary for their living during rainy *** results also show that in fluvial systems with high discharge variations,the boundaries between a“pre-desiccation suite”and a“desiccation suite”in the Scoyenia ichnofacies can be diffuse due to the short duration of colonization windows and progressive terrestrialization of floodplains and ***,the frequency of flooding events,the lowered water table,and the rapidity of substrate desiccation constrained colonization by other burrowers and may be considered as firstorder factors controlling the generation of a monotypic *** ***,the monotypic Taenidium ichnofabric in the Scoyenia ichnofacies context is an ichnomarker of brief windows for colonization in highly seasonal environments.

关键词： Ichnology Paleopedology Continental ichnofacies Meniscate burrows ichnofabric

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ichnofabrics and Their Environmental Interpretation from the Fluvial Deposits of the Middle Triassic Youfangzhuang Formation in Western Henan, Central China

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Journal of Earth Science 2014年第4期25卷 648-661页

作者： Min Wang Yongan Qi Da Li Mingyue Dai Yuguang Chang Institute of Resources and Environment Henan Polytechnic University

Fluvial deposits from the Middle Triassic Youfangzhuang Formation in Henan Province, China contain a low-diversity trace fossils. Vertical dwelling burrows of opportunists dominate in active channel, whereas horizontal deposit-feeding, grazing, and vertical dwelling burrows occur in overbank deposits. Seven recurrent ichnofabrics were distingushed. The Palaeophycus tubularis ichnofabric pre- serves below scour interface between two fluvial cycles. The Skolithos linearis ichnofabric forms in middle to high-energy, soft substrates in the middle and upper parts of active channel deposits under semi-arid climate. The Skolithos linearis-Planolites montanus ichnofabric occurs in the sediments just a little above the Skolithos linearis ichnofabric and is formed in middle-energy, soft substrates in the up- per part of active channel deposits. The Planolites montanus ichnofabric is mostly preserved in associa- tion with medium- to thick-bedded brown-red silty mudstones or siltstones in low-energy, perennial muddy bottom ponds in overbank settings. The Taenidium barretti ichnofabric is interpreted as peri- odically exposed ephemeral ponds or low-energy distal floodplain. The Skolithos isp. ichnofabric com- monly occurs in middle to high-energy firm ground of proximal foodplain or crevasse-splay deposits. The root trace iehnofabric occurs in the crevasse splay deposits. The presence of thin palaeosols and the abundance of calcretization in mudstones indicate a seasonal climate ranging from humid to semi-arid, with high temperature, rainfall, and well-defined dry and wet seasons.

关键词： trace fossil ichnofabric fluvial deposit environmental interpretation Middle Triassic Youfangzhuang Formation.

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