Cyclic Sedimentation Patterns in the Middle and Upper Ordovician Trenton Group of Central Pennsylvania

Three crinoids are known from the Upper Ordovician Hatter Limestone at Union Furnace in central Pennsylvania, i.e., Haptocrinus buttsi n. sp., an unknown crinoid with a lichenocrinid holdfast, and an indeterminate columnal that probably belongs to a crinoid. Two crowns enable H. buttsi n. sp. to be reconstructed. The animal lived about 70 cm above the seafloor and was attached to a strophomenid brachiopod with a lichenocrinid holdfast. Its endotomous arms formed an efficient filtration net that covered much of the water within its planar filtration fan. The application of filtration theory indicates that H. buttsi n. sp. could begin to feed at a comparatively low ambient current velocity and balance its energy budget. Like many other ramulate disparids, H. buttsi n. sp. mainly collected moderately small food particles. As a member of the Tornatilicrinidae, H. buttsi n. sp. is a relatively primitive disparid. Another crinoid taxon bears a longer and thinner stem and a different type of lichenocrinid holdfast cemented to the same strophomenid shell. A third species, most likely a crinoid, is represented by a single columnal. The fauna lived in a quiet water lagoonal area, which is an unusual habitat for Paleozoic crinoids.

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Provenance of Upper Ordovician (Richmondian) Bald Eagle and Juniata Formations, Central Pennsylvania: Implications for Nature of Taconian Orogeny in Central Appalachians: ABSTRACT

AAPG Bulletin ◽

10.1306/ad461ab1-16f7-11d7-8645000102c1865d ◽

1984 ◽

Vol 68 ◽

Author(s):

Richard R. Leon

Keyword(s):

Bald Eagle ◽

Upper Ordovician ◽

Central Appalachians ◽

Central Pennsylvania

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Diachronous tectonic collapse of the Ordovician continental margin, eastern Canada: comparison between the Quebec Reentrant and St. Lawrence Promontory

Canadian Journal of Earth Sciences ◽

10.1139/e94-113 ◽

1994 ◽

Vol 31 (8) ◽

pp. 1309-1319 ◽

Cited By ~ 56

Author(s):

Denis Lavoie

Keyword(s):

Continental Margin ◽

Foreland Basin ◽

Head Group ◽

Upper Ordovician ◽

Eastern Canada ◽

Middle Ordovician ◽

Carbonate Sedimentation ◽

Shallow Subtidal ◽

Thickness Variations ◽

Trenton Group

The Upper Ordovician Trenton Group of southern Quebec represents the last Taconian foreland basin carbonate unit in the Quebec Reentrant, prior to final collapse of Laurentia's continental margin and its burial under synorogenic flysch. The Trenton Group, either conformably or unconformably, overlies the Black River Group and is in turn conformably overlain by the Utica Shales. The tripartite Trenton carbonate unit records progressive deepening: (1) very shallow to shallow subtidal, (2) shallow to deep carbonate ramp, and (3) shallow to deep outer shelf. Regional facies distribution, lithotectonic elements, and thickness variations indicate that the Trenton shelf was dissected by extensional faults delineating blocks subsiding at various rates. This scenario compares favourably with Taconian foreland basin development in the Middle Ordovician Table Head Group at the St. Lawrence Promontory, Newfoundland. A similar stratigraphic succession and tectono-sedimentary history occurring 10–15 Ma earlier at the St. Lawrence Promontory than in the Quebec Reentrant argues for a primary tectonic control for the demise of carbonate sedimentation at the margin. The diachroneity in the foreland evolution can be related to the irregular morphology of the Laurentia continental margin.

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