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Pedogenic and lacustrine features of the Brushy Basin Member of the Upper Jurassic Morrison Formation in western Colorado: Reassessing the paleoclimatic interpretations

Tanner L., Galli K., Lucas S.

Volumina Jurassica

2014

Vol. 12, no. 2

115--130

Study of the pedogenic features of the Upper Jurassic Morrison Formation in western Colorado, USA, shows a clear difference in the types of paleosols between the strata of the lower and upper Brushy Basin Member. Lower Brushy Basin paleosols are mostly calcareous Aridisols with Stage I through Stage III calcrete Bk horizons, abundant root traces, occasional vertic features, but only rarely with ochric epipedons. Upper Brushy Basin paleosols are mainly thicker and commonly display ochric epipedons and well-developed Bt and Bw horizons. We assign these paleosols to the order Inceptisol. Limestones occur in the Brushy Basin Member and include both uniformly micritic limestones and limestones with strongly brecciated textures. The former contain sparse body fossils and charophyte debris, while the latter are characterized by clotted-peloidal fabrics with circumgranular cracking and silica replacement. We interpret these limestones as the deposits of carbonate in small water bodies on a low-gradient flood plain, with the textures resulting from pedogenic reworking of the carbonate sediment. We find no evidence for the presence of extensive lacustrine or wetlands (Lake T’oo’dichi’) deposits in the study area. The paleoclimate suggested by all of these features is strongly seasonal, but subject to variations on orbital (precessional and higher) timescales causing intervals of semi-aridity during weaker monsoons, to alternate with sub-humid periods during stronger monsoons. The apparent long-term change in climate during Brushy Basin deposition potentially resulted from northward drift of North America.

Trace elements in soils of various ecosystems of the Siedlce Upland

Raczuk J., Deska J.

Chemia i Inżynieria Ekologiczna

2000

Vol. 7, nr 11

1229-1236

The total content and distribution orMo, Zn, Co, Pb, Ni, Cr in soils of various ecosystems of the Siedlce upland was investigated. The study was condueted on 6 profiles exhibiting different physico-chemical properties. The mean content of Mn, Zn, Pb, Cr, Co, Ni in the investigated soils are: 227; 30.8; 17.9; 12.2; 9.0; 5.9 mg/kg d.m. respectively. The highest level of enrichment in Mn, Zn, Pb and Cu in relation to their contenIs in the parent rocks displayed humus horizons of the meadow black earths. The contents and distribution of the trace elements in the soil horizons are connected with the lithogenesis and pedogenesis as well as, in case of Pb, to some extent with anthropogenesis.

Badano zawartość Mn, Zn, Cu, Pb, Ni, Cr w glebach ekosystemów leśnych, łąkowych i pól uprawnych Wysoczyzny Siedleckiej. Badaniami objęto 6 profilów glebowych charakteryzujących się zróżnicowanymi właściwościami fizykochemicznymi. Średnia zawartość Mn, Zn, Pb, Cr, Cu i Ni w badanych glebach wynosiła odpowiednio: 227; 30,8; 17,9; 12,2; 9,0 oraz 5,9 mg/kg s.m. Największe wzbogacenie w Mn, Zn, Pb, i Cu w stosunku do ich zawartości w skale macierzystej wykazują poziomy próchniczne gleb ekosystemów łąkowych. Stwierdzono, że na zawartość pierwiastków śladowych w analizowanych glebach wpłynęła litogeneza, pedogeneza oraz w przypadku Pb antropogeneza. Słowa kluczowe: gleby płowe, brunatne, gruntowo-glejowe, czarne ziemie, części spławialne, pedogeneza, litogeneza, antropogeneza