The phrase "a threshold between" is correct and usable in written English.
It can be used to describe a point of transition or boundary separating two different states, conditions, or concepts.
Example: "The study explores a threshold between childhood and adolescence, highlighting the significant changes that occur during this period."
Alternatives: "a boundary between" or "a divide between".
For example, analysis of data from the 20 largest U.S. cities between 1987 and 1994 provided no evidence for a threshold between PM10 and daily cardiorespiratory mortality (Schwartz and Zanobetti 2000; Schwartz et al. 2002).
Almost everything in this ballet is on a threshold between abstraction and realism, happiness and fear.
Cut from the earth, it swallows the sky, its high plateaus serving as a threshold between the two.
Despite the often grisly circumstances of death, Mr. Serrano invests these images with a luminous beauty, reminding us that in the Christian tradition, death is simply a threshold between two states of being.
Every writer establishes a threshold between major and minor characters, significant and arbitrary fates, but it's perhaps a weakness of the book that this divide coincides with a sectarian one.
In fiction, the seaside frequently represents a threshold between order and chaos, society and nature, identity and its loss, with a move or visit to the coast signalling a shift from the former to the latter.
And for Geoffrey it's a place of "big tents like Roy said all done of branches and tarps," a threshold between town and forest, between Geoffrey's failed assimilation and his eventual exile.
And on those occasions when Mortimer does paint a face, he achieves a supreme sense of ambivalence, of being on a threshold between oppositional emotions: "expression has to be exactly right, and it's very hard to find that expression – between orgasm and fear and death, or worry or anguish – without having to show it".
This requires the application of a threshold between forested and non-forested land.
