FOSSILIZATION MODEL FOR SQUAMASTROBUS TIGRENSIS FOLIAGE IN A VOLCANIC-ASH DEPOSIT: IMPLICATIONS FOR PRESERVATION AND TAPHONOMY (PODOCARPACEAE, LOWER CRETACEOUS, ARGENTINA)

LAFUENTE DIAZ, MAITEN, A; D ÁNGELO, JOSÉ; GEORGINA M. DEL FUEYO; ERWIN ZODROW

PALAIOS

SEPM-SOC SEDIMENTARY GEOLOGY

Lugar: Lawrence; Año: 2018 vol. 33 p. 323 - 337

0883-1351

The present study is a holistic approach to the relationship between volcaniclastic host rockcharacteristics and the fossilization processes of short leafy coniferous branches of Squamastrobus tigrensis, preservedas fossilized-cuticles (Lower Cretaceous, Baquer´o Group, Patagonia, Argentina). The question of diagenetic influencesof Aptian volcaniclastic sedimentation on preservation chemistry and taphonomic processes is addressed. Whereasinfrared spectroscopy provided chemical information on the leaves, vitrinite reflectance and complementary thermalindicators provided data on the thermal maturity of the dispersed organic matter in the host rock. Three sample typeswere analyzed: fossilized-cuticle, macerated fossilized-cuticle (by infrared spectroscopy), and associated organic hostrock matter (by light microscopy). Results clearly show chemical variability between, and within the fossilized-cuticleand cuticle, as well as a similarity to type I/II kerogen, i.e., high contents of both aliphatic groups and oxygencontainingcompounds. Combined with the lower maturity of the host rock, the importance of the depositionalenvironment during burial and taphonomic conditions that affected the fossilization of S. tigrensis are summarized ina general fossilization model.