The phrase "an upper stratum" is correct and usable in written English.
It can be used to refer to a higher layer or level within a hierarchy, often in contexts like sociology, geology, or organizational structures.
Example: "In the study of social dynamics, the upper stratum of society often holds more power and influence over decision-making processes."
Alternatives: "a higher layer" or "an elevated tier".
Smokestack industries did disappear; jobs came to be divided between a lower stratum of service workers and an upper stratum sitting in antiseptic bubbles playing with computers.
Important events in its development were the realization by English engineer and geologist William Smith that in a horizontal sequence of sedimentary strata what is now an upper stratum was originally deposited on a lower one and the discovery by Scottish geologist James Hutton that an unconformity (discontinuity) indicates a significant gap in time.
Two distinct vegetation strata are identifiable, an upper stratum dominated by Acacia tortilis, A. nilotica, A. polyacantha and A. seyal, and a lower stratum of grasses, herbs and forbs.
On the other hand, even in open aristocracies there is a tendency for the upper stratum to become a hereditary group filled mainly by the offspring of aristocratic parents.
Democrats offered a less sanguine view of the labor market, asserting that most Americans were still enduring paltry raises and that the Republican tax plan was a boon only to the upper stratum of the country.
In certain special environments a single species dominates the upper stratum.
After drying in a baking oven, the composite upper stratum scaffold was soaked in sodium hyaluronate solution for 24 hours, so that it was absorbed by the upper layer.
Being widely distributed over most body sites, this type II keratin is expressed late, at an advanced stage of differentiation, in the uppermost epidermal layers (upper stratum spinosum, stratum granulosum) to a variable extent (Collin et al. 1992a).
After the solvent had completely evaporated, the scaffold was soaked in de-ionised water for 48 hours, and a porous composite scaffold material comprising both upper stratum and substratum was obtained.
For many years, from Emancipation through the imposition of onerous racial restrictions by the Wilson Administration, climaxing in a brutal, white-sparked riot following the First World War, the upper stratum of the city's black population held to a proto-Harlem Renaissance ideal: demonstrate how civilized, intelligent, and accomplished we are, and racism will fade away.
They can in turn extrapolate information about the general circulation of the upper stratum of the ocean from a synoptic view of the surface pressure field.
