| Popis: |
There is not yet a precise classification of or terminology for ecostratigraphic boundaries. SHE analysis for biozone identification (SHEBI) objectively places boundaries between abundance biozones (ABs). Alpha diversity ( = SE = eH, where H is the information function) measures the community diversity within an AB in units of effective species, whereas the dimensionless β diversity ( = SE2/SE1, where SE1 and SE2 are the α diversities of successive ABs) quantifies the difference in α diversity between successive ABs. Three categories of AB boundary are recognized depending on the value of β. In Type –1β, the α diversity of the younger AB is significantly less than that of the older. In Type 0β, SE2 ≈ SE1, while in Type +1β, the α diversity of the younger AB is significantly greater than in the older. Benthonic foraminifera were sampled from the ∼124-m-thick Pleistocene strata of DSDP Hole 148 (eastern Caribbean Sea). SHEBI indicated 18 ABs; of the 17 AB boundaries, seven were Type –1β, two wer... |
