Portland Sand Formation

{{short description|Geological formation in Dorset, England}}

{{Use dmy dates|date=April 2022}}

{{Infobox rockunit

| name = Portland Sand Formation

| image =

| caption =

| type = Group

| age = Tithonian, {{fossilrange|152}}

| period = Tithonian

| prilithology = Dolomite

| otherlithology = Siltstone, limestone and sandstone

| namedfor = Isle of Portland

| namedby =

| region = England

| country = {{flag|UK}}

| coordinates =

| unitof = Portland Group

| subunits =

| underlies = Portland Stone Formation

| overlies = Kimmeridge Clay Formation

| thickness = up to {{Convert|40|m|ft|-1}}

| extent = Dorset

| area =

| map =

| location_ts = Clay Ope, West Weare Cliff, Isle of Portland

| thickness_ts = 30 m

| map_caption =

}}

The Portland Sand Formation is a limestone formation from the Tithonian stage of the Jurassic period on the Isle of Portland, Dorset, England.{{Cite web |url=https://www.bgs.ac.uk/lexicon/lexicon.cfm?pub=POSA |title=Portland Sand Formation |last=British Geological Survey |website=BGS Lexicon of Named Rock Units |access-date=29 June 2020}} The formation is made up largely of dolomites but includes siltstones and fine-grained sandstones in its lower parts.Barton et al., 2011 Geology of south Dorset and south-east Devon and its World Heritage Coast. Special memoir of the British Geological Survey. Sheets 328, 341/2, 342/3 and parts of 326/340, 327, 329 and 339 (England and Wales) It is a sub unit of the Portland Group.Callomon, J H and Cope, J C W. 1995. The Jurassic geology of Dorset. 51-103 in Taylor, P D (Editor), Field Geology of the British Jurassic. (Bath: The Geological Society.)