T57 Future Leaders in Paleontology

Sunday, 15 October 2023
1:30 PM - 5:30 PM
303

INTO- OR OUT-OF-INDIA? EARLY EOCENE POLLEN AND MACROFOSSILS FROM THE GHAZIJ FORMATION IN BALOCHISTAN, PAKISTAN TEST LONG-STANDING BIOGEOGRAPHIC HYPOTHESES

Paper number: T57-11
Program: Technical Sessions
Time: 3:50 PM – 4:05 PM

Authors

Abstract

The early Cenozoic collision of the Indo-Pakistan Tectonic Plate into Asia and resulting biotic exchange hypothetically contributed to the immense biodiversity of South and Southeast Asia. Proposed out-of-India plant lineages include Dipterocarpaceae, Durio, Alangium, and Ctenolophon. However, well-constrained pollen and macrofossil data from Indo-Pakistan are rare, limiting support for these hypotheses. Additionally, diverse mammalian assemblages from the early Eocene (ca. 54–50 Ma) Ghazij Formation in Balochistan, Pakistan, on the northwestern plate margin, show a contrasting into-India dispersal pattern. The endemic faunas of the middle Ghazij were replaced by Holarctic taxa, found in the upper Ghazij, as the collision progressed. Here, we present a preliminary report on the first plant macrofossils and palynofloras from the Ghazij Formation, collected from the same magnetostratigraphically-constrained sequence as the mammalian faunas. The 41 palynological samples were collected directly from the paleomagnetic sample splits through the middle and upper Ghazij, and the macrofossils (13 sites, ca. 382 specimens) were concentrated in the upper Ghazij Fm. These fossil sites, sampled in 2000, are no longer accessible due to regional conflict. The palynofloras indicate an environmental transition through the formation from coastal or nearshore marine, to coastal palm swamps, coastal peatlands, and increasingly terrestrial nearshore ecosystems. Diverse dinocyst fossils, including Apectodinium homomorphum, Enneadocysta spp., and Areosphaeridium sp. reaffirm the early Eocene age of the formation. Notable palynomorphs recovered include Nypa, Euphorbiaceae, Chloranthaceae, Dipterocarpaceae and Alangium in the middle Ghazij; and Salvinia, Nypa, Croton, and Onagraceae from the upper Ghazij. The leaf flora (ca. 25 species) is dominated by a probable Sapindales morphotype and contains Salvinia leaves, several palm morphotypes, Fabaceae, and possible Calophyllum. Our preliminary findings show diverse coastal vegetation with several hypothesized out-of-India taxa in the middle Ghazij (Dipterocarpaceae, Alangium), from a time of limited mammalian interchange with Asia, supporting the prior hypothesis that these plant taxa were present in India before its collision with Asia.

Geological Society of America Abstracts with Programs. Vol. 55, No. 6

doi: 10.1130/abs/2023AM-395130

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