What do the letter symbols represent?
Each color on the map represents a surficial material with a distinct texture and origin. Each geologic unit was deposited in a specific time period and has its own mix of surficial materials (sand, gravel, till, etc.). The letter symbols are made up of two elements: a capital letter at the beginning followed by one or more lower case letters (Figure 5). The age of deposition is represented by the capital letter at the beginning of the label: P – Pleistocene, Q – Quaternary; H – Holocene (geologic time chart). The remaining lower-case letters in the label refer either to the composition of the unit (e.g. Pt – Pleistocene till; Ha – Holocene alluvium) or to its origin and morphology (e.g. Pmd – Pleistocene marine delta; Pge – Pleistocene eskers; Pem – Pleistocene end moraines).
