High-Resolution Stratigraphy of an Underfilled Lake Basin: Wilkins Peak Member, Eocene Green River Formation, Wyoming, U.S.A.

摘要: Abstract Lakes tend to respond noticeably minor changes in sediment and water balance driven by climatic, tectonic, or geomorphic processes. This unique behavior of lacustrine basins can provide a high-resolution record geologic processes within the continental setting, far from globally averaged marine strata. The Wilkins Peak Member Eocene Green River Formation, Wyoming, USA, is dominated aggradation repetitive sedimentary facies successions recording distinct expansions contractions. These "cycles" consist up four successive associations: littoral, profundal–sublittoral, palustrine, salt pan. Because they comprise disparate that may never have been simultaneously deposited basin, cycles are non-Waltherian do not readily equate any established sequence stratigraphic unit. completeness varies continuously across basin. At least 126 present ERDA White Mountain #1 core near basin depocenter, whereas only about one third as many recognizable 53 km north, nearer margin. Cycle boundaries terminate northward gradual amalgamation into palustrine facies, reflecting interplay between varying lake levels south-dipping deposition gradient. Evidence for complete desiccation hiatuses commonplace even center; truly be anywhere. Based on recent 40Ar/39Ar geochronology tuffs, average cycle duration approximately 10,000 years. However, true shorter due presence lacunae, time required thinnest less than 1000 No external driving mechanism presently known such short duration, raising possibility instead autogenic related instability surrounding landscape. Evaporite corresponded closely space maximum differential subsidence, suggesting tectonic influences drainage patterns accommodation exerted primary control. Differential was most pronounced during lower became progressively so after time. structural observations, period increased uplift commenced concurrent with Member.