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Specworld's "K-T" Stratigraphy

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"The history of the world, my sweet is who gets eaten and who gets to eat." - Stephen Sondheim, Sweeney Todd

Most Spec-researchers continue to use a stratigraphic system based on the one developed and calibrated for Home-Earth sedimentary formations. This system is workable in the contexts of either timeline, as the broad geological and climatic histories of our two worlds---with the exception of the K-T boundary---appear to be identical. For example, the timing of the appearance and disappearance of the index fossils (various marine planktonic forms) that help to demarcate the different stages of the Cenozoic show a strong degree of correspondance between the two timelines. It should be noted that the actual makeup of the Cenozoic planktonic floras of Spec and RL are very different, however the arrival and extinction of stratigraphically useful taxa happens at about the same time.

There remains one glaring geological difference that separates Spec from RL - 65 million year old sedimentary deposits on Spec show no sign of a large impact event or the subsequent mass-extinctions. In fact, discounting the long-term decline of certain lineages and a drop in marine tropical diversity, there appear to be no abrupt changes in the global biota between about 71 million to 63 million years ago. This low-level extinction roughly corresponds on the RL chronological sequence with the start of the Maastrichtian Age (the final stage of the Late Cretaceous) to several million years into the Paleocene Epoch (the first Epoch of the Cenozoic Era). Especially noticeable is the continued formation of chalk deposits in Spec during this time whereas, in RL, all chalk production suddenly ceases after the K-T boundary, due to the sudden disappearance of radiolarians (chalk-producing planktonic organisms). Just as striking is the complete absence on Spec of the famous band of iridium-rich deposits, the ominous global signature of the K-T impact.

Largely for reasons of convenience, many Spec-based research publications continue to use Home-Earth K-T stratigraphy and chronology (ie. the Cretaceous Period ends 65 million years ago) for describing the corresponding sections of sediment and past-time on Spec even though the physical geological boundaries do not exist (ie. there is nothing in the 65 million year old sediments of Spec that would warrant the termination of the Mesozoic Era and the start of the Cenozoic Era). As a result of this anomaly, some researchers have proposed a number of amendments to the stratigraphic table of Specworld to account for these striking differences:

  1. The end of the Cretaceous Period (and thus the Mesozoic Era as well) on Spec is pulled forwards from c. 65 million years ago to c. 55 million years ago, corresponding to the end of the Paleocene Epoch in RL.
  2. The period of time on Specworld corresponding to the first 3 million years of the Paleocene on RL is now incorporated into the Maastrichtian Age of the Cretaceous. Thus the Maastrichtian, which extends from 72-65 million years ago in RL, extends from 72-62 million years ago on Spec.
  3. The remainder of Spec’s Paleocene, (extending from 62-55 million years ago) is retained as a distinct unit owing to changes in planktonic assemblages. It is however, considered to be the final age of the Cretaceous Period rather than a part of the Cenozoic Era. A large extinction event (albeit less drastic than RL's K-T event) at the end of this age marks the end of the Mesozoic Era and the dawn of the Cenozoic Era on Spec.
  4. From after 55 million years ago, the stratigraphic units of Spec once again conform with those of RL save for the fact that the Eocene is now considered to be the first Epoch of the Paleogene/Cenozoic.

However, these amendments have yet to be widely accepted and, rather than risk confusion to the reader in this introductory publication, we will henceforth continue to use the Home-Earth chronostratigraphic system.

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