The La Brea tar pits are well known for the animals ensnared in them but there are also trees, bits of trees, branches, and various bits of vegetation equally entrapped as much as the animals – but trees don't walk and get themselves stuck in tar. It's a bit like scientists did not really want you to know about the flora in the tar pits as they had decided the animals had got their by their own volition, trapped like flies in treacle. What else are the tar pits hiding? At http://phys.org/print280656705.html … the veil is lifted because scientists wanted to study the flora rather than the fauna, and you've guessed, they wanted to measure the rate of growth of the trees as it is assumed there was a lower level of co2 in the atmosphere during the Ice Ages. It is all part of CAGW funded research but in this instance opens a window on something much more interesting. Trees, in California, during the glacial era, display no evidence of inhibited growth. This was something of a surprise as co2 levels are generally touted as much lower during the Late Glacial Maximum. The ice sheet never penetrated as far south as California – but it is assumed global temperatures were much cooler and therefore it would have been fairly cold even in regions where it is very warm nowadays. None of this would dispute the idea that during that period the Poles were further south than they are today – nor would the fact that junipers were the species of tree hauled out of the tar pits. At the same time none of this can be used as evidence of Poles moving. What has been gleaned is that co2 levels during the Ice Ages may not have been as low as theorised – globally.