Boxplots for the mean near-core chemical elemental signatures (³¹P, ¹³⁸Ba, ⁸⁶Sr and ²⁴Mg) for all samples. Pairwise comparisons among sampling events for each trace element are represented by letters. Among sampling events, when the events share a letter, there is no significant difference between them. Horizontal lines indicate median values. Within the boxes, the upper lines indicate the quartile 3 and the lower lines indicate the quartile 1.