Integrating Paleobotanical, Paleosol, and Stratigraphic Data to Study Critical Transitions: A Case Study From The Late Cretaceous–Paleocene Of India

Abstract

During the Cretaceous and Paleogene, the Indian subcontinent was isolated as it migrated north from the east coast of Africa to collide with Asia. As it passed over the Reunion hotspot in the late Maastrichtian–early Danian, a series of lava flows extruded, known as the Deccan Traps. Also during this interval, there was a major mass-extinction event at the Cretaceous–Paleogene boundary, punctuated by a meteorite impact at Chicxulub, Mexico. What were the biological implications of these changes in paleogeography and the extensive volcanism in terms of biodiversity, evolution, and biogeography? By combining chronostratigraphic, paleosol, and paleobotanical data, an understanding of how the ecosystems and climates changed and the relative contributions of the Chicxulub impact, Deccan Traps volcanism, and paleogeographic isolation can be gained. Understanding relative ages of paleobotanical localities is crucial to determining floristic changes, and is challenging because different methods (e.g., magnetostratigraphy, radiometric dating, vertebrate and microfossil biostratigraphy) sometimes give conflicting answers, or have not been done for paleobotanical localities. Climatic data can be obtained quantitatively by studying paleosol geochemistry, as well as qualitatively by examining functional traits and nearest living relatives of fossil plants. An additional challenge is revising macrofossil data, which includes some confidently identified taxa and others with uncertain affinities. This is important for understanding ecosystem composition both spatially and temporally, as well as the biogeographic implications of an isolated India.

Oldest fruit of Phyllanthaceae from the Deccan Intertrappean Beds of Singpur, Madhya Pradesh, India

“…The specimen was recovered from chert at the locality of Singpur, ca 60 km northwest of Nagpur, central India. Singpur is among numerous paleobotanical localities exposed in the Deccan Intertrappean beds of central India representing flora that existed immediately prior to and following the Cretaceous-Tertiary boundary (Prakash 1960, Smith et al 2015. The Singpur locality is likely of late Maastrichtian age based on the palynological correlation (Samant et al 2008).…”

Faunal elements from the Deccan volcano‐sedimentary sequences of India: A reappraisal of biostratigraphic, palaeoecologic, and palaeobiogeographic aspects

“…These megafloral evidences (e.g., Palmoxylon woods, Brachyphyllum leaves, Viracarpon fruits, and Araucaria seeds) have been mainly recorded from the Mohgaon‐Kalan intertrappeans or adjoining sections of the Mandla sub‐province and attest presence of sub‐tropical to tropical vegetation in the region. Detailed studies on the anatomical features of the silicified woods (mainly from the Mandla sub‐province) suggest prevalence of a mesic, subtropical to tropical climate during the deposition of the DVSS in the sub‐province (Smith et al, ). These inferences were also supported subsequently by Wheeler, Srivastava, Manchester, and Baas (), who carried out a detailed examination of thin sections of >40 species of permineralized wood specimens belonging to families, viz., Anacardiaceae, Achariaceae, Lamiales (Lamiaceae), Simaroubaceae; subfamilies, viz., Planchoideae (Lecythidaceae), Leeoideae (Vitaceae), and Myrtoideae (Myrtaceae); and tribes, viz., Grewioideae, Sterculioideae (Malvaceae), and Castilleae (Moraceae).…”

“…It is pertinent to mention here that there exists a long history of research (intitiated during the early half of the 20th century) on the permineralized megafloral remains (silicified woods, chertified fruits, and flowers) from the DVSS in a palaeoecologic context (Manchester, Kapgate, & Wen, 2013 prevalence of a mesic, subtropical to tropical climate during the deposition of the DVSS in the sub-province (Smith et al, 2015).…”

Morphology and anatomy of the angiosperm fruit Baccatocarpon, incertae sedis, from the Maastrichtian Deccan Intertrappean Beds of India

“…The Deccan Intertrappean Beds of India preserve a rich fossil record of plants which spans the Cretaceous/Paleogene boundary (Kapgate 2005, Srivastava 2012, Smith et al 2015. Determining the species composition of the floras in pre-and post-boundary localities will help us to assess plant response to local and global environmental perturbations.…”

“…In the continuing investigation of multiple localities of the Deccan Intertrappean beds of central India (Kapgate 2005, Smith et al 2015, several plant taxa have been found to be shared among localities considered to represent the late Maastrichtian flora. These include the angiosperms Enigmocarpon (Sahni 1943), "Musa" cardiospermum (Jain 1963), Graminocarpon (Chitaley & Sheikh 1971), Indovitis (Manchester et al 2013), Pantocarpon (Kapgate et al 2007, Manchester et al in press), Sahnipushpam (revised, Kapgate et al 2011) and Viracarpon (revised, Matsunaga et al 2018).…”