THE KALKBERG FORMATION (HELDERBERG GROUP, L. DEV., LOCHKOVIAN) AT CHERRY VALLEY, NEW YORK IS ACTUALLY NEW SCOTLAND - PRELIMINARY RESULTS OF SEDIMENTOLOGIC AND STRATIGRAPHIC INVESTIGATIONS

Helderberg strata mapped as the Kalkberg Fm. on U.S. 20 at Cherry Valley, NY comprise limey siltstones, silty carbonate mudstones to wackestones with chert, calcareous shale interbeds and six K-bentonites. Insoluble residues (predominantly quartz silt) from these beds range from 35 to 83%. Intense bioturbation is prevalent with many burrows displaying linings up to 5 mm thick. A sparse but diverse shelly fauna (brachiopods, bryozoans, trilobites, bivalves, sponges, rare corals) occurs as disarticulated, unabraded bioclasts. Skeletal debris increases up section. Overall, these beds resemble the New Scotland Fm. more than they do the Kalkberg Fm.

The lower third of the U.S. 20 outcrop is characterized by dm-scale pinch and swell bedding, interpreted as broad, symmetrical ripples with remnants of low angle, form-concordant cross stratification, similar to HCS. The rest of the unit exhibits tabular dm beds which are commonly cherty.

The sedimentology, paleontology, taphonomy and ichnology of the U.S. 20 strata suggest deposition on an open, storm-dominated shelf with significant siliciclastic input. Depths were below normal wave base but above storm wave base. Shallowing of the shelf is recorded by increased quantity, size and diversity of bioclasts in beds immediately below the Wallbridge Unconformity (base of Oriskany Sandstone). Quartz silt content (average 26%) is decreased in this subunit.

Westward from the Hudson Valley, onlap of middle Helderberg units onto the Punch Kill Unconformity (PKU, top of the Coeymans Fm.) is evident by the progressive disappearance of the 1) chert zone at the base of the Kalkberg Fm. (lower Hannacroix Mbr.), 2) upper Hannacroix Mbr. and 3) Dicoelosia shales at the base of the Broncks Lake Mbr. of the Kalkberg Fm. Skeletal packstones above the PKU north of U.S. 20 at Cherry Valley likely represent a thin remnant of the upper Broncks Lake Mbr. Therefore, the strata on U.S. 20 are correlative with the siltstone facies of the lower New Scotland Fm. The highest beds in the U.S. 20 exposure may correlate with the limier upper New Scotland.

Lithology and regional stratigraphic relationships indicate that the “Kalkberg” at Cherry Valley is, in fact, the New Scotland Fm. Recognition of these strata as New Scotland will facilitate correlation of the mid-Helderberg K-bentonites in the Appalachian Basin.