On protracted Laurentian rifting, continental freeboard, and cap carbonates in Neoproterozoic time

Our understanding of Neoproterozoic Earth is in a state of flux. Low-latitude glaciation, breakup of the supercontinent Rodinia, and the origin and diversification of metazoans are some of the events that occurred during late Neoproterozoic time (ca. 750 Ma through 542 Ma), though understanding these events has so far proven challenging; almost every issue regarding the Neoproterozoic Era is currently debated and lacks consensus. This dissertation adds to several Neoproterozoic topics.; I investigate the depositional controls (tectonic and/or glacio-eustatic), isotope stratigraphy, and age of the Neoproterozoic Reed Dolomite, White-Inyo Mountains, eastern California. The Reed Dolomite is comprised of, in stratigraphic order, the Lower Member, the Hines Tongue, and the Upper Member. The Lower Member's basal contact is likely ca. 560 Ma. In some locations the Lower Member indicates a tectonic influence on deposition, including carbonate breccia from the Lower Member itself and associated normal faulting. The Hines Tongue follows as a coarse, arkosic unit that pinches out from the southeast to the northwest and can be interpreted as recording a dramatic change in relative base level, possibly related to decay of a thermal anomaly related somehow to extensional tectonism. The Upper Member indicates deposition during tectonic quiescence, and is considered to be ca. 548 Ma. New high-resolution C-isotope data show an oscillatory, positive delta13C trend from approximately +1 per mil (VPDB) to +2 per mil (VPDB) through the Lower Member that rapidly climbs and maintains at +3 per mil (VPDB) with the onset of the Hines Tongue, and then decreases to ∼+1.5 per mil (VPDB). The most parsimonious explanation of these lithostratigraphic relationships during Reed Dolomite deposition is extensional tectonism. This is supported by the Lower Member breccia, thermal subsidence rates, dramatic lateral thickness variations in the Lower Member, and previous chemostratigraphic correlations tying the Lower Member of the Reed Dolomite to incision of the Johnnie Formation of the Death Valley succession to the east, where workers have identified extensional tectonism as well. I interpret this extensional tectonism to be most consistent with protracted Laurentian rifting followig the breakup of Rodinia.; Though at first glance many Neoproterozoic observations seem quite disconnected, they are qualitatively consistent with a dramatic increase in continental exposure and weathering. I consider the combined effects of continental freeboard and hypsometry on continental exposure, and expand on the discussion of the effects of increased continental silicate weathering and erosion on Neoproterozoic Earth systems.; The style of a Neoproterozoic cap carbonate does not necessarily indicate when it was deposited, thus, contrary to popular practice, cap carbonates should not be used as chronostratigraphic markers.