Uppermost Cambrian-lower Ordovician faunas and Laurentian platform sequence stratigraphy, eastern New York and Vermont

Abstract

The Cambrian–Ordovician boundary is a type 1 depositional sequence boundary with dramatic local erosional incision in restricted marine facies on the easternmost New York Promontory. The systemic boundary is bracketed below by Late Cambrian, upper Cordylodus proavus Zone (s.s). conodonts from carbonates of the upper Little Falls Formation (=Whitehall Formation, abandoned). Presumed Lower Ordovician ellesmeraceratoid cephalopods from the upper Little Falls are uppermost Cambrian and among the oldest known in North America. The overlying deepening–shoaling cycle of the Tribes Hill Formation (=Cutting and Great Meadows Formations, abandoned) is the local expression of a lowermost Ordovician (Rossodus manitouensis Zone) depositional sequence recognizable across Laurentia. Complete replacement of conodonts takes place in the late Tremadocian or Tremadocian–Arenigian boundary interval with onlap of the “Fort Ann Formation” across the paleokarst cap of the Tribes Hill. The trilobites Hystricurus sp. and Symphysurina myopia Westrop new species occur in less restricted, thrombolitic facies of the middle Tribes Hill that have the highest conodont diversity. Ulrichodina Furnish, 1938, emend. is regarded as the senior synonym of the conodont Colaptoconus Kennedy, 1994 (=Glyptoconus Kennedy, 1980).

Onset of the Ordovician cephalopod radiation – evidence from the Rochdale Formation (middle Early Ordovician, Stairsian) in eastern New York

“…The Rochdale Formation is one of the least areally extensive formations of the Beekmantown Group in this region. Landing & Westrop (2006;also Landing, 2002;Landing, Westrop & Van Aller Hernick, 2003;Landing, Westrop & Keppie, 2007) determined that the Tribes Hill Formation, the lowest Ordovician unit of the Beekmantown Group, was deposited during a eustatic high that submerged Laurentia as far as Wisconsin and Minnesota in late early Tremadocian times. However, the next overlying Beekmantown Group formation is a depositional sequence that records a late Tremadocian eustatic high that did not lead to transgression west of the roughly N-S line defined by the modern Hudson River-Lake Champlain lowlands (Fig.…”

“…Ulrich et al (1944) reported the proterocamerocerid Cotteroceras Ulrich et al 1944, from the Roubidoux Formation in the Ozark region of Missouri. The Roubidoux spans the Low Diversity Interval-Macerodus dianae Zone (conodonts) and is approximately timeequivalent with the Rochdale Formation (Repetski, Loch & Ethington, 1998;Landing, Westrop & Van Aller Hernick, 2003). The Longview Limestone of Virginia from which Ulrich et al (1944, p. 16) reported a number of pilocerids and proterocamerocerids is probably time-equivalent to the Rochdale Formation.…”

“…The group comprises a succession of unconformity-bounded, relatively thin (about 60 m or less) depositional sequences (Landing, Westrop & Knox, 1996;Landing, Westrop & Van Aller Hernick, 2003) and yields some of the oldest cephalopod faunas in North America. These cephalopods from the upper part of the Late Cambrian Little Falls Formation (Rathbunville Limestone member) and unconformably overlying Early Ordovician Tribes Hill Formation (late Skullrockian Stage and late early Tremadocian Series) have been recently described , with the latter unit yielding a relatively high-diversity ellesmerocerid assemblage.…”

Terminal Cambrian and lowest Ordovician succession of Mexican West Gondwana: biotas and sequence stratigraphy of the Tiñu Formation

“…Development of a strongly dysoxic mid-water mass on continental slopes is recorded during this interval (middle-late part of the early Tremadoc) of high eustatic levels (Landing, Benus & Whitney, 1992;Landing, Westrop & van Aller Hernick, 2003), and an onlap of this low-oxygen water is apparently recorded by the lower Río Salinas Member.…”

“…This sea-level rise is apparently eustatic, as it correlates with sea-level rise within the Rossodus manitouensis Chron that drove shorelines into the upper Mississippi River valley region in Laurentia (Landing, Benus & Whitney, 1992;Ross & Ross, 1995;Landing, Westrop & van Aller Hernick, 2003;Landing & Westrop, 2006) and across Baltica during the 'early to middle Tremadoc highstand interval' (Nielsen, 2004). Development of a strongly dysoxic mid-water mass on continental slopes is recorded during this interval (middle-late part of the early Tremadoc) of high eustatic levels (Landing, Benus & Whitney, 1992;Landing, Westrop & van Aller Hernick, 2003), and an onlap of this low-oxygen water is apparently recorded by the lower Río Salinas Member.…”