An integrative physical, mineralogical, and ichnological approach to characterize underfilled lake-basins

MANCUSO, ADRIANA CECILIA; MARSICANO, CLAUDIA; BENAVENTE, CECILIA A.; KRAPOVICKAS, VERÓNICA

SEDIMENTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2020

0037-0746

Lakes are particularly sensitive to environmental fluctuations, which are recorded in their facies and stratigraphy. Ephemeral lakes reveal their sensitivity to paleoenvironmental changes in the overprinting of the sedimentary features in every single bed. Tetrapod-track taphonomic-modes and ichnological taphonomic-pathways can be used as sensitive indicators of environmental conditions of the track-bearing beds during deposition and imprinting. The Middle Triassic Cerro de las Cabras succession (Cuyana Basin, Argentina) provides an excellent opportunity to these environmental indicators in an underfilled paleolake. A model of ichnological preservation for underfilled lake systems is proposed and evaluate the role of ichnology record in the sequence stratigraphy analysis, based on the integration of tetrapod-track modes, taphonomic-pathways of playa-lake ichnofauna, mineralogy, and physical data. Soft-ground suites include those dominated by invertebrate grazing traces and arthropod locomotion traces (Suite 1), and those overprinted by horizontal-vertical dwelling burrows with tetrapod tracks preserved in taphonomic modes B and C (Suite 2). The firm-ground suite (Suite 3) comprises tetrapod-tracks with the best preservation styles (modes A and B) along less abundant invertebrate dwelling and feeding traces as found in Suite 2. Clay mineralogy (dominated by illite with subordinate smectite) suggests low plasticity of the layers, in agreement with low-relief deformation structures observed in tetrapod-track taphonomic-modes. The well-preserved track tetrapod features documented in the Cerro de las Cabras succession, together with the absence of pedogenic disturbance, trampling obliterating the footprints, and/or evidence of strong disturbance by wind, desiccation, and/or precipitation, supports short periods of exposure of the imprinted surface particularly to this succession. It is proposed an integrated multiproxy approach to evaluate the evolutionary interpretation and identification of autogenic versus allogenic controls in underfilled lake-basin histories. The observed aggradational-trend suggests an equilibrium between rates of accommodation change and sediment supply, and the basin-centre did not experience prolonged sediment-starved conditions.