page_title: Puddingstone (rock)
section_title: Jasper conglomerate
hierarchical_section_title: Puddingstone (rock) / Jasper conglomerate
caption_attribution_description: Jasper-quartz pebble conglomerate in the Precambrian of Ontario, Canada. Southeastern Canada's ~2.3 billion year old Lorrain Formation includes some beautiful rocks that rockhounds have nicknamed &quot;puddingstone&quot;. This refers to whitish-gray quartzites having common pebbles of red jasper. The Lorrain Formation is somewhat heterolithic. Published studies mention that the unit has arkoses, subarkoses, quartzites, and jasper-pebble conglomerates. The latter two lithologies are present at the glacially-eroded outcrop seen here. The quartzites were originally sandstones. They have been well cemented and somewhat metamorphosed into very hard rocks. The jasper-pebble conglomerates, or &quot;puddingstones&quot;, include clasts of white quartz and reddish jaspilites. Jaspilite is a type of BIF (banded iron formation). BIFs only formed on Earth during the Precambrian - most are Paleoproterozoic in age. They are the # 1 source of iron ore for the world's steel industry. Numerous specific types of BIFs are known. Jaspilite consists of alternating laters of red and silvery-gray, iron-rich minerals. The red layers are hematite or jasper (= hematitic chert). The silver-gray layers are usually rich in magnetite and/or specular hematite. Jaspilite BIFs outcrop in many areas around Lake Superior, for example in Michigan's Upper Peninsula, Minnesota, and Ontario. During the Paleoproterozoic, BIFs were subaerially exposed as paleo-outcrops and eroded, producing BIF sediments, including many red jasper pebbles. These mixed with quartz-rich sediments. Regional studies indicate that the Lorrain Formation was deposited in ancient shallow ocean, lake, delta, and shoreline environments. Stratigraphy: Lorrain Formation, upper Cobalt Group, Huronian Supergroup, Paleoproterozoic, ~2.3 Ga Locality: Ottertail Lake Northeast Roadcut - glacial knob on the eastern side of Rt. 638, northeast of Ottertail Lake &amp; southeast of Rock Lake, north-northeast of the town of Bruce Mines, southern Ontario, southeastern Canada (46° 23' 30.59&quot; North latitude, 83° 43’ 10.94&quot; West longitude) Some info. synthesized from: Hadley (1970) - Paleocurrents and origin of Huronian Lorrain Formation, Ontario and Quebec. American Association of Petroleum Geologists Bulletin 54: 850.
context_page_description: Puddingstone, also known as either pudding stone or plum-pudding stone, is a popular name applied to a conglomerate that consists of distinctly rounded pebbles whose colors contrast sharply with the color of the finer-grained, often sandy, matrix or cement surrounding them. The rounded pebbles and the sharp contrast in color gives this type of conglomerate the appearance of a raisin or Christmas pudding. There are different types of puddingstone, with different composition, origin, and geographical distribution. Examples of different types of puddingstones include the Hertfordshire, Schunemunk, Roxbury, and St. Joseph Island puddingstones.
context_section_description: Jasper conglomerate, which is also denominated "pebble jasper conglomerate", "Saint Joseph Island puddingstone", "Drummond Island puddingstone", or "Michigan(ian) puddingstone", occurs in Saint Joseph Island and the vicinity of the Saint Mary's River, north and northwest of the Bruce Mines of Northern Ontario, Canada, circa 65 kilometres (40 mi) east of Sault Sainte Marie, Ontario. In these locales, it occurs as thick beds of Paleoproterozoic pebble conglomerate within the medial part of a geologic formation that is named the Lorrain Formation of the Cobalt Group. The jasper conglomerate consists of subrounded pebbles of red jasper, black chert, white quartzite, hematite, and semi-transparent quartz in a matrix of coarsely grained quartzite. It contains circa 30% to 90% of pebbles. Within the deposits of Lorrain Formation, the jasper conglomerates occur principally as the sedimentary fills of erosional troughs and channels of what are interpreted to be either alluvial fans or deposits of braided river. These deposits are inferred to be nonglacial in origin and immediately postdate the Paleoproterozoic Makganyene glaciation.
  Elsewhere, e. g. in Drummond Island, Michigan, United States, jasper conglomerate, there denominated "Drummond Island puddingstone", occurs as loose gravel within Pleistocene glacial drift. These fragments of jasper conglomerate are glacial erratics that continental ice sheets from Northern Ontario eroded and then spread throughout Michigan, including in Drummond Island, and as far south as Ohio and Kentucky during repeated glacial advances and retreats.
caption: Jasper-quartz pebble conglomerate from Ontario, Canada
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