Fig. 4
From: VOLCORE, a global database of visible tephra layers sampled by ocean drilling
Number of tephra occurrences in 500 ka bins, normalised to the percentage of drill holes with material of that age. This normalisation removes the bias of there being more tephra recorded in recent times due to there being more core material from those times. Part A shows the whole record, back to 150 Ma, part B zooms in on the last 50 Ma and part C on the last 20 Ma. The tephra used in these plots are those with a content of ‘ash’, ‘ash-rich’, ‘ash-bearing’ and ‘ashy’. The tephra occurrences with ‘tuffaceous’ content (not shown here) create a peak at around 30 Ma that may represent erosion and reworking.
