Macrofauna and biostratigraphy of the Rollrock Section, northern Ellesmere Island, Canadian Arctic Islands – a comprehensive high latitude archive of the Jurassic–Cretaceous transition

Abstract

The Rollrock Section in the Sverdrup Basin, Arctic Canada, is one of the northernmost outcrops where the Jurassic-Cretaceous transition is accessible. The over 500 m thick sedimentary succession exposes the Oxfordian to Valanginian Ringnes and Deer Bay formations. Macrofauna from 15 discrete horizons includes ammonites, Buchia bivalves and belemnites. These fossils improve the biostratigraphy of the Tithonian and Berriasian in the Sverdrup Basin, provide correlation to the remainder of the Boreal Realm and set reliable calibration points. The occurrence of Buchia rugosa in the Ringnes Formation moves the upper formation boundary of from the top of the Kimmeridgian into the lower Tithonian. Dorsoplanites maximus and D. sachsi document the middle Tithonian Dorsoplanites maximus Zone in Arctic Canada for the first time. The late Tithonian to early Berriasian Buchia terebratuloides is considered to be the best approximate indicator of the Jurassic-Cretaceous transition in the Rollrock Section. The middle early Berriasian Praetollia maynci and the late early Berriasian Borealites fedorovi tie the respective horizons to the successive Chetaites sibiricus and Hectoroceras kochi zones. Two species of the belemnite Arctoteuthis, collected from an interval with glendonites, suggest a Valanginian age for the upper Deer Bay Formation. The dearth of Late Jurassic to earliest Cretaceous macrofossils in the Sverdrup Basin is inferred to be predominantly a function of diagenetic carbonate loss. Abundant dropstones and glendonites in the middle Tithonian to middle Valanginian interval suggest cold climatic conditions, and make the Rollrock Section a prime candidate for studying the Arctic environmental perturbations of this time.

Sequence stratigraphy and microplankton palaeoenvironmental dynamics across the Jurassic–Cretaceous transition in the Canadian Arctic

“…Sequence 3 was dated as Tithonian-Berriasian by Ingrams et al (2021). Several macrofossil horizons occur within the regressive systems tract of this sequence, containing ammonites and Buchia bivalves described in detail in Schneider et al (2020), which confirm the Tithonian-Berriasian age. This sequence correlates with sequence 10 of Embry (1993) and the base Tithonian sequence of (Table 3).…”

“…At 251 m, there is a sharp contact between the fine-grained sandstones and overlying mudstones. This change in lithology marks the boundary between the Ringnes and Deer Bay formations (Schneider et al 2020). The Deer Bay Formation consists of dark, thinly bedded or laminated mudstones.…”

“…A sandstone bed containing large concretions at 273 m and a thin indurated siltstone interval are the only interruptions to mudstone deposition. Palynological and macrofossil evidence gives a Tithonian-Valanginian age for the Deer Bay Formation (Schneider et al 2020;Ingrams et al 2021). Eight horizons of glendonites, which have been described as the most distinguishing aspect of the upper Deer Bay Formation by Kemper (1975), have been recorded from the upper part of the Rollrock Section (Schneider et al 2020), and palynological evidence identifies these as Valanginian in age (Ingrams et al 2021).…”

“…The Rollrock Section, Arctic Canada, is one of the highest palaeolatitude continuous sections spanning the Jurassic-Cretaceous transition, and the northernmost section in the Sverdrup Basin (Schneider et al 2020;Ingrams et al 2021). Previous palynological studies of assemblages recovered from the basin focused entirely on biostratigraphy (Ingrams et al 2021) and/or had less complete sections, lower sample numbers or more widely spaced samples (Davies 1983;Galloway et al 2013Galloway et al , 2015Nguyen et al 2020).…”

Permafrost in the Cretaceous supergreenhouse

“…Most evidence of a Cretaceous cryosphere comes in the form of marine ice-rafted debris (IRD) from the southern 6,7 and northern hemispheres [8][9][10][11] , as well as from the recognition of marine glendonites (calcite pseudomorphs after ikaite) indicating cold temperatures during formation [12][13][14][15] . Additional evidence includes Cretaceous landforms in Yukon and Alaska 16 , patterned ground in China 17 , and ice-rafted dropstones in desert oases indicating colddesert conditions in interdunes similar to those in the Badain Jaran Desert 11 .…”