Mitigating the Goldilocks effect: the effects of different substrate models on track formation potential

Area of Science:

• Ichnology
• Sediment Mechanics
• Paleontology

Background:

• The Goldilocks effect in ichnology posits that substrate properties must be optimal for track formation.
• Substrates that are too soft or too firm prevent track preservation.
• Substrate homogeneity is rarely observed in nature, with variations in layers and mechanical behaviors like strain hardening being common.

Purpose of the Study:

• To investigate the specificity of the Goldilocks effect using virtual substrates.
• To explore how realistic soil parameters, such as strain hardening and vertical heterogeneity, influence track formation.
• To determine the range of trackmaker sizes capable of leaving imprints under varying substrate conditions.

Main Methods:

• Finite-element analysis was employed to simulate virtual substrates.
• Models incorporated elastic-perfectly plastic behavior, strain hardening, and vertical heterogeneity.
• Simulations analyzed the relationship between underfoot pressure, substrate properties, and track preservation.

Main Results:

• Inclusion of strain hardening in models slightly increased the potential range of trackmaker sizes compared to simple models.
• Simulating vertically heterogeneous, strain hardening substrates significantly expanded the range of potential trackmakers.
• Realistic soil parameters were shown to lessen the constraints of the Goldilocks effect.

Conclusions:

• The Goldilocks effect is less restrictive when considering more realistic soil parameters like strain hardening and heterogeneity.
• While realistic parameters expand the range, upper and lower limits for trackmaker size still exist for successful imprinting.
• This study refines our understanding of factors controlling trace fossil preservation in ichnology.