YAMAMA FORMATION SECTION

[Yamama Formation reference section was measured and sampled in detail by R.W. Power and H.A. McClure in 1962 near vicinity of type section about 20 km south of Al Yamamah]

Calcirudite of the Buwaib Formation (Lower Cretaceous).
Unconformity.		Thickness
Yamama Formation:		(meters)
3. Calcarenite and aphanitic limestone (16.0 m thick):
	Pellet calcarenite, golden-brown, well-sorted, fine-grained, sparsely sandy ................................................................	3.0
	Covered; rare exposures of off-white, chalky, aphanitic limestone; upper 0.5 m forms cap of off-white nodular limestone ……………………......……......……....……	3.4
	Aphanitic limestone, light-brown, tight, 5 percent sponge spicules. Oyster bed 1.1 m below top. ………………..	1.6
	Pellet-foraminifera calcarenite, brown, moderately well-sorted, tightly cemented; 20 percent tabular disarticulated pelecypod values showing strong lineation parallel to bedding and set in matrix of medium- to coarse- grained, pellets and Foraminifera all tightly cemented with clear secondary calcite hill-capping unit……....…….....	0.4
	Calcareous sandstone, golden-brown, tight, quartzose; 50 percent fine- to medium- grained, subrounded to angular quartz sand uniformly admixed with lime-mud matrix..…..	0.6
	Covered ……………......……......……......……........	1.0
	Pellet calcarenite, golden-brown, well-sorted, fine-grained, rounded cemented; abundant calcite-replaced monaxon sponge spicules and scattered pelecypod debris….........	1.5
	Covered ……………......……......……......……........	2.0
	Pellet calcarenite, golden-brown, moderately well-sorted, medium- to coarse-grained, tightly cemented, clean-washed; 5 percent coarse pelecypod debris and Foraminifera commonly scattered through the pellet calcarenite matrix………………....................................	2.0
	Pellet calcarenite, dark-golden-brown, well-sorted, very fine grained, tightly cemented; calcarenite so uniformly sorted and tightly cemented that on outcrop appears as aphanitic limestone with well-developed conchoidal fracture. Rare chert nodules. Extensive bench former; bed caps all hills in the area……………….…….…….……...	0.5
2. Aphanitic and calcarenite limestone (10.1 m thick):
	Aphanitic limestone, tan, moderately porous, chalky; slightly sandy....................................................................	1.5
	Coarse pelecypod calcarenitic limestone, tan to medium-brown, tight, poorly sorted; 50 percent disarticulated pelecypod valves, Foraminifera and pellets in a light-cream- colored, lime-mud matrix. Isolated pockets of clean, current-washed, tightly cemented Foraminifera- pellets calcarenite. Pelecypod debris replaced by clean crystalline calcite. Echinoids rather common……………..	1.0
	Aphanitic limestone, light-tan, moderately porous, chalky..	0.7
	Foraminifera-pellet calcarenite, golden-brown, tightly cemented, well-sorted; 5 percent recrystallized pelecypod shells……………………………....................................	0.5
	Aphanitic limestone, light-tan, moderately porous, sparsely sandy; abundant monaxon (?) sponge spicules scattered throughout; very rare molluscan debris…………………...	1.3
	Calcarenite and limestone; tan, strongly cemented, well sorted pellet calcarenite intimately interbedded with coarse molluscan calcarenitic limestone as below. Gastropods and Foraminifera uniformly scattered through both rock types. Weathered bench surface contains abundant, well- preserved pelecypods, echinoids, and scarce ammonites. Pygurus cf. P. rostraius common ...................................	0.5
	Coarse molluscan calcarenitic limestone, brown, tight, poorly sorted; 50 percent calcite-replaced, gravel-sized pelecypod and gastropod shells randomly oriented in lime-mud matrix and commonly infilled with lime mud. Forms brown, biogenic limestone bench………………...	2.5
	Partly covered; probably off-white, soft, chalky, aphanitic limestone…………………………..................................	2.1
	Aphanitic limestone, tan, moderately porous, chalky; slightly sandy....................................................................	1.5
	Coarse pelecypod calcarenitic limestone, tan to medium-brown, tight, poorly sorted; 50 percent disarticulated pelecypod valves, Foraminifera and pellets in a light-cream- colored, lime-mud matrix. Isolated pockets of clean, current-washed, tightly cemented Foraminifera-pellets calcarenite. Pelecypod debris replaced by clean crystalline calcite. Echinoids rather common ……	1.0
	Aphanitic limestone, light-tan, moderately porous, chalky ..	0.7
	Foraminifera-pellet calcarenite, golden-brown, tightly cemented, well-sorted; 5 percent recrystallized pelecypod shells……………………………...................................	0.5
	Aphanitic limestone, light-tan, moderately porous, sparsely sandy; abundant monaxon (?) sponge spicules scattered throughout; very rare molluscan debris…………………	1.3
	Calcarenite and limestone; tan, strongly cemented, well sorted pellet calcarenite intimately interbedded with coarse molluscan calcarenitic limestone as below. Gastropods and Foraminifera uniformly scattered through both rock types. Weathered bench surface contains abundant, well-preserved pelecypods, echinoids, and scarce ammonites. Pygurus cf. P. rostraius common.................	0.5
	Coarse molluscan calcarenitic limestone, brown, tight, poorly sorted; 50 percent calcite-replaced, gravel-sized pelecypod and gastropod shells randomly oriented in lime-mud matrix and commonly infilled with lime mud. Forms brown, biogenic limestone bench………………...	2.5
	Partly covered; probably off-white, soft, chalky, aphanitic limestone…………………………..............................	2.1
1. Calcarenite and coarse carbonate (19.4 m thick):
	Pellet-molluscan calcarenite, golden-brown, moderately well-sorted, fine-grained, strongly laminated, tightly cemented; disarticulated pelecypod valves show definite lineation parallel to laminations. Foraminifera and gastropod debris common. Very thin bed of pelecypod calcarenitic limestone near top. Upper 0.3-m-thick bed forms prominent dip slope.................................................	3.3
	Coarse gastropod carbonate, brown, poorly sorted; moderately cemented; 60 percent gastropod remains commonly infilled with cream-colored lime mud. Some gravel-sized fragments of tan aphanitic limestone apparently derived from older limestone. About 20 percent fine- to medium- grained Foraminifera…………………...	1.6
	Pellet calcarenite, golden- to reddish-brown, generally well-sorted, tightly cemented, very fine to medium-grained; Foraminifera and molluscan debris common. Occasional thin beds of brown, poorly sorted, tightly cemented, coarse-grained to gravel-sized, coarse gastropod carbonate. Single 0.3-m-thick bed of golden-tan, tight aphanitic limestone 2.7-3.0 m below top of interval ...........	9.5
	Covered……………………………………………...	1.0
	Pellet calcarenite, as below, top of unit forms extensive dip slope………………………………………………...	1.5
	Covered……………………………………………...	1.0
	Pellet calcarenite, brown, poorly sorted, tightly cemented, poorly preserved arenaceous Foraminifera common. About 20 percent of debris is of organic origin, dominantly molluscan…………………………………………........	1.5
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	Total thickness of Yamama Formation.…………….…	45.5
Sulaiy Formation