@article {1008,
	title = {Chemostratigraphy of Paleoproterozoic carbonate successions of the Wyoming Craton: tectonic forcing of biogeochemical change?},
	journal = {Precambrian Research},
	volume = {120},
	year = {2002},
	note = {id: 1586},
	pages = {279-325},
	abstract = {The Archean Wyoming Craton is flanked on the south and east by belts of Paleoproterozoic supracrustal successions whose correlation is complicated by lack of geochronologic constraints and continuous outcrop. However, carbonate units in these successions may be correlated by integrating carbon isotope stratigraphy with lithostratigraphy. The \~{}10 km thick Paleoproterozoic Snowy Pass Supergroup in the Medicine Bow Mountains was deposited on the present-day southern flank of the Wyoming Craton; it contains three discrete levels of glacial diamictite correlative with those in the Huronian Supergroup, on the southern margin of the Superior Craton. The Nash Fork Formation of the upper Snowy Pass Supergroup is significantly younger than the uppermost diamictite and was deposited after the end of the Paleoproterozoic glacial epoch. Carbonates at the base of the Nash Fork Formation record remarkable 13C-enrichment, up to +28{\textperthousand} (V-PDB), whereas those from overlying members of the lower Nash Fork Formation have δ13C values between +6 and +8{\textperthousand}. Carbonates from the upper Nash Fork Formation above the carbonaceous shale have carbon isotope values ranging between 0 and +2.5{\textperthousand}. The transition from high carbon isotope values to those near 0{\textperthousand} in the Nash Fork Formation is similar to that at the end of the ca. 2.2{\textendash}2.1 Ga carbon isotope excursion in Fennoscandia. This chemostratigraphic trend and deposition of BIFs, Mn-rich lithologies, carbonaceous shales and phosphorites at the end of the global ca. 2.2{\textendash}2.1 Ga carbon isotope excursion are likely related to ocean overturn associated with the final breakup of the Kenorland supercontinent. Correlative carbonates from the Slaughterhouse Formation in the Sierra Madre, WY, and from the Whalen Group in the Rawhide Creek area in the Hartville Uplift, WY, have highly positive carbon isotope values. In contrast, carbonates from other exposures of the Whalen Group in the Hartville Uplift and all carbonate units in the Black Hills, SD, have carbon isotope values close to 0{\textperthousand}. Combined with existing geochronologic and stratigraphic constraints, these data suggest that the Slaughterhouse Formation and the succession exposed in the Rawhide Creek area of the Hartville Uplift are correlative with the lower and middle Nash Fork Formation and were deposited during the ca. 2.2{\textendash}2.1 Ga carbon isotope excursion. The Estes and Roberts Draw formations in the Black Hills and carbonates from other exposures in the Hartville Uplift postdate the ca. 2.2{\textendash}2.1 Ga positive carbon isotope excursion and are most likely correlative with the upper Nash Fork Formation. The passive margin, on which the carbonates with highly positive carbon isotope values were deposited, extended around the southern flank of the Wyoming Craton through the Sierra Madre, Medicine Bow Mountains and Hartville Uplift. The presence of carbonates with carbon isotope values close to 0{\textperthousand} in the upper Nash Fork Formation and the Whalen Group indicates that the passive margin persisted on the southern flank of the Wyoming Craton after the carbon isotope excursion. Rifting in the Black Hills, likely related to the final breakup of the Kenorland, succeeded the carbon isotope excursion, since the Estes and Roberts Draw formations, deposited during rifting and ocean opening on the eastern flank of the Wyoming Craton, postdate the carbon isotope excursion.},
	keywords = {Biogeochemistry, Chemostratigraphy, Kenorland, Paleoproterozoic, Wyoming},
	doi = {10.1016/S0301-9268(02)00164-X},
	author = {Bekker, A. and Karhu, J. A. and Eriksson, A. and Kaufman, A. J.}
}
@article {857,
	title = {Sedimentary Cycling and Environmental-Change in the Late Proterozoic - Evidence from Stable and Radiogenic Isotopes},
	journal = {Geochimica Et Cosmochimica Acta},
	volume = {56},
	year = {1992},
	note = {Hj963Times Cited:357Cited References Count:100},
	month = {Mar},
	pages = {1317-1329},
	abstract = {We report C, Sr, and O isotopic as well as selected major and trace element data from Late Proterozoic (ca. 900-540 Ma) marine carbonates in three widely separated basins.  The isotopic and elemental data are used to evaluate effects of post-depositional alteration of Sr-87/Sr-86 and delta-C-13.  Using our present best estimates for unaltered samples, we construct a new delta-C-13-curve for 850 500 Ma marine carbonates using data in this paper and from literature sources.  Delta-C-13 values are high (+4 to +8 parts per thousand) during most of the late Riphean (ca. 900-600 Ma) with brief negative excursions likely associated with glacial periods.  Similarly, in the Vendian delta-C-13 falls sharply (from late Riphean highs) to < -3 parts per thousand around the Varanger glaciation (ca. 600 Ma), and then returns to high values (+4 to +2 parts per thousand) remaining until the Precambrian-Cambrian boundary where the curve drops to a value of about -1 parts per thousand in Lower Cambrian carbonates.  Coupling of the Sr and C isotopic data is used to develop a simple model for evaluating organic carbon (C(org)) burial in Late Proterozoic oceans.  These calculations indicate that C(org) burial rates were lower than present-day values during much of the late Riphean, at the same time that erosion rates were low.  Excess O2 produced by the burial of C(org) was likely balanced by oxidation of reduced hydrothermal fluids and weathering reactions.  Near the time of the Varanger glaciation, C(org) burial rates dropped but quickly recovered and reached a maximum (a factor of 2-4 greater than present day) in Vendian sediments.  High C(org) burial rates were probably driven by high sedimentation rates, and possibly high productivity.  The high C(org) burial rate likely gave rise to a large flux of O2; high values of delta-S-34 in Late Proterozoic marine sulfates suggest that this O2 flux was not balanced by increased sulfate formation.  Further, the Sr-isotopic record indicates that excess O2 was not balanced by oxidation of submarine hydrothermal fluids.  Increased oxidative weathering was probably an important sink for O2; nonetheless, we conclude that a significant and rapid increase in atmospheric O2 occurred in the Vendian.  These results have important implications for environmental changes during the first appearance of an Ediacaran metazoan fauna.},
	issn = {0016-7037},
	doi = {10.1016/0016-7037(92)90064-P},
	author = {Derry, L. A. and Kaufman, A. J. and Jacobsen, S. B.}
}
