Syn‐rift mass flow generated ‘tectonofacies’ and ‘tectonosequences’ of the Kingston Peak Formation, Death Valley, California, and their bearing on supposed Neoproterozoic panglacial climates

Abstract

The Kingston Peak Formation of the Pahrump Group in the Death Valley region of the Basin and Range Province, USA, is the thick (over 3 km) mixed siliciclastic-carbonate fill of a long-lived structurally-complex Neoproterozoic rift basin and is recognized by some as a key 'climatostratigraphic' succession recording panglacial Snowball Earth events. A facies analysis of the Kingston Peak Formation shows it to be largely composed of 'tectonofacies' which are subaqueous mass flow deposits recording cannibalization of older Pahrump carbonate strata exposed by local faulting. Facies include siltstone, sandstone and conglomerate turbidites, carbonate megabreccias (olistoliths) and related breccias, and interbedded debrites. Secondary facies are thin carbonates and pillowed basalts. Four distinct associations of tectonofacies ('base-of-scarp'; FA1, 'mid-slope'; FA2, 'base-of-slope'; FA3, and a 'carbonate margin' association; FA4) reflect the initiation and progradation of deep water clastic wedges at the foot of fault scarps. 'Tectonosequences' record episodes of fault reactivation resulting in substantial increases in accommodation space and water depths, the collapse of fault scarps and consequent downslope mass flow events. Carbonates of FA4 record the cessation of tectonic activity and resulting sediment starvation ending the growth of clastic wedges. Tectonosequences are nested within regionally-extensive tectonostratigraphic units of earlier workers that are hundreds to thousands of metres in thickness, recording the long-term evolution of the rifted Laurentian continental margin during the protracted breakup of Rodinia. Debrite facies of the Kingston Peak Formation are classically described as ice-contact glacial deposits recording globally-correlative panglacials but they result from partial to complete subaqueous mixing of fault-generated coarse-grained debris and fine-grained distal sediment on a slope conditioned by tectonic activity. The sedimentology (tectonofacies) and stratigraphy (tectonosequences) of the Kingston Peak Formation reflect a fundamental control on local sedimentation in the basin by faulting and likely earthquake activity, not by any global glacial climate.

Field evidence suggests that the Palaeoproterozoic Gowganda Formation in Canada is non-glacial in origin

“…Hence, diamictites have often been regarded as tillites, or at least as having originated from glaciogenic processes, without thorough consideration of other possible interpretations. This inference has often been based on hypotheses of palaeoclimatic interpretations (see e.g., Jensen & Wulff-Pedersen, 1997;Arnaud & Eyles, 2004;Eyles & Januszczak, 2007;Carto & Eyles, 2012;Kennedy & Eyles, 2021), followed by association and interpretation of diamictite deposits displaying matrix-supported clasts (note: some geologists also label mixtures of sediment which are clast-supported as diamictite), striated pavements and presence of supposed dropstones as glaciogenic. If a research area was originally considered to have been influenced by glaciers, the geomorphological, depositional and deformational data from nearby outcrops were often, by default, interpreted on the basis of that scenario.…”

“…Many researchers refer to the hypothesis of Snowball Earth, for which the Gowganda Formation is an important area in worldwide correlations (Young, 2013(Young, , 2014. However, the evidence for Snowball Earth scenarios is equivocal, as has been confirmed by detailed dating of outcrops of Neoproterozoic (Le Heron et al, 2020) and Palaeoproterozoic strata, including the Gowganda Formation (Kump et al, 2013;Young, 2014Young, , 2019, by the geochemical record (Bahlburg & Dobrzinski, 2011;Bristow et al, 2011;Grotzinger et al, 2011;Zimmermann et al, 2011), including (mainly for Neoproterozoic and younger strata) ikaites/glendonites -the minerals that are supposed to be stable only in cold temperatures (Aspler et al, 2001;Hoffman, 2013;Fairchild et al, 2016), but are documented to have formed in temperate and even tropical waters (Popov et al, 2019) and, lastly, by numerous studies of the geology of Precambrian diamictites (e.g., Eyles, 1993;Molén, 2017;Kennedy et al, 2019;Kennedy & Eyles, 2021).…”

“…clasts, a correlation between clast size and thickness of sedimentary strata and sedimentary structures. Diagnostic criteria were described by Schermerhorn (1974), but also in much more recent literature concerning diamictites (e.g., Kennedy & Eyles, 2021;Molén, 2021). Varves can only be diagnosed with certainty if these display evidence of yearly deposition, but laminated formations can form diurnally from tidal water and in turbidites (e.g., Eyles & Januszczak, 2007;Shanmugam, 2016;Smith & Bailey, 2018).…”

“…Varves can only be diagnosed with certainty if these display evidence of yearly deposition, but laminated formations can form diurnally from tidal water and in turbidites (e.g., Eyles & Januszczak, 2007;Shanmugam, 2016;Smith & Bailey, 2018). Dropstones and clasts transported within gravity flows can be diagnosed only if there are visible sedimentary structures which can be examined, like a disturbance of sediments or penetration of laminae (e.g., Thomas & Connell, 1985;Kennedy & Eyles, 2021), but an outsized clast in massive sediment may always be interpreted either as transported enclosed within a gravity flow or by ice and deposited as a dropstone.…”

Ice-rafted dropstones in “postglacial” Cryogenian cap carbonates

“…The clast clusters are interpreted as sedimentary pellets (Tomkins et al, 2008). Although there is a tradition of recognising "outrunner clasts" from debris flows where an ice-rafted mechanism is not appealing (Kennedy and Eyles, 2020), this process cannot explain granule and pebble-sized clasts in laminated dolomicrites. This is because although hydroplaning beneath much larger-scale "outrunner blocks" e.g.…”