non-sequence
/nɒnˈsiːkw(ə)ns/noun
1Absence of (a recognized) sequence; an instance of this.
2 Geology. Interruption in the deposition of adjacent conformable strata that was too short (in geological terms) for significant erosion to take place and consequently has to be inferred from a gap in the fossil record; an instance of this.
Origin
Late 19th century; earliest use found in Philosophical Transactions of the Royal Society of London. From non- + sequence.