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The work formed part of a new survey of Gävleborg province by the Swedish Geologic Survey, with primary attention on the lake bed and secondary examination of previously known outcrops on land. Specially used diver equipment and its operational constraints are described, alongside physiological diving procedures governing safe descent, staged ascent, and prevention of decompression sickness.",{"@graph":69,"@context":123},[70,84,106],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/a-petrological-investigation-in-lake-norra-dellen-preface-and-introduction/145902/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/a-petrological-investigation-in-lake-norra-dellen-preface-and-introduction/145902.png","ImageObject",300,407,{"name":92,"@type":93},"\tWilliam","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-01","2026-08-26",true,{"@type":102,"interactionType":103,"userInteractionCount":105},"InteractionCounter",{"@type":104},"ViewAction",13,{"@type":107,"mainEntity":108},"FAQPage",[109,115,119],{"name":110,"@type":111,"acceptedAnswer":112},"What was the main goal of the underwater investigation in Lake Norra Dellen?","Question",{"text":113,"@type":114},"To apply geologic research methods—surveying and taking specimens—to an underwater region, focusing on the Dellen andesite and mapping the lake bed.","Answer",{"name":116,"@type":111,"acceptedAnswer":117},"Why is staged ascent important during deep diving?",{"text":118,"@type":114},"At depths around 10–40/50 m, nitrogen dissolves in the blood in larger quantities; a rapid ascent can cause decompression sickness, which is avoided by ascending in stages and pausing for decompression.",{"name":120,"@type":111,"acceptedAnswer":121},"What physiological limitation can occur at depths greater than about 30–50 m?",{"text":122,"@type":114},"Nitrogen narcosis, which can cause an intoxication-like effect, altered sensations of air, reduced work ability, and impaired judgment; the paper notes this can be mitigated by using other gas mixtures such as oxygen and helium.","https://schema.org",{"og:url":83,"og:type":125,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":127,"canonical":83},"index,follow",{"doc_id":129,"site_id":62},145902,1787732213,{"code":4,"msg":5,"data":132},{"doc_id":129,"user_id":133,"nickname":92,"user_avatar":134,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":135,"file_id":136,"file_url":137,"file_type":138,"file_size":139,"view_count":105,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":140,"language":141,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":142,"faqs":143,"seo_title":144,"seo_description":67,"update_tm":130,"read_time":26},5909887254083,"https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","| SER.C   | Avhandlingar och uppsatser   | N:0548   |\n| --- | --- | --- |\n\nARSBOK 50(1956)N:04  \nA PETROLOGICAL INVESTIGATION  \nIN LAKE NORRA DELLEN  \nBY MEANS OF  \nFROG-MAN EQUIPMENT  \nLEONARDO L.REDAELLI  \nPris 2 kronor  \nSVERIGES GEOLOGISKA UNDERSÖKNING  \n\n| SER.C   | Avhandlingar och uppsatser   | N:0548   |\n| --- | --- | --- |\n\nARSBOK 50(1956)N:04  \nA PETROLOGICAL INVESTIGATION  \nIN LAKE NORRA DELLEN  \nBY MEANS OF  \nFROG-MAN EQUIPMENT  \nLEONARDO L.REDAELLI  \nPreface  \nThis investigation was originally carried out as an examination work for themining engineer's degree at the Royal Institute of Technology,Geological Section,head Prof.O.H.Ödman.The practical purpose of my work has been a petrologicalmapping of the bottom of Lake Norra Dellen for the Geological Survey of Sweden,director Prof.N.H.Magnusson,on the proposal of Dr P.H.Lundegardh,who hasmapped the surrounding Archean bed-rock.I should like to express my gratitude tothese three persons,who have been lively interested in my work.Further,I haveto direct my deep thanks to Disponent G.Sundblad of the Iggesunds Bruks Ltd,who has provided me with raft,compressor,tug,and necessary workers.The RoyalSwedish Navy has put at my disposal a complete diver's equipment.My gratitudeis here especially directed to Lieutenant B.Cassel and Eng.B.Östergren.  \nFinally,I will call into remembrance the good job of my co-workers during thefield investigation.  \nContents  \nIntroduction……………………………………………………………………………………………………………………………………………………5  \nThe physiological aspects of diving………………………………………………………………………………6  \nProcedure………………………………………………………………………………………………………………………………………………7  \nConclusions regarding procedure………………………………………………………………………………………II  \nGeneral remarks on Lake Norra Dellen…………………………………………………………………………………I2  \nTopographical description ……………………………………………………………………………………………………I4  \nGeological and petrographic description………………………………………………………………………………I5  \nDescription of rocks………………………………………………………………………………………………………………………I6  \nGroup I: Breccia and tuffs…………………………………………………………………………………………I6  \nGroup II:Devitrified andesite……………………………………………………………………………………I7  \nGroup III:Glassy andesites…………………………………………………………………………………………………I9  \n# Introduction\n\nThis paper is concerned with an attempt to apply geologic research methods(surveying and taking of specimens)to an underwater region —in this case thewell-known Dellen andesite.The work was carried out in Lake Norra Dellen andformed part of a new survey of Gävleborg province by the Swedish Geologic Survey.The investigation was concentrated mainly to the lake bed,but four previouslyknown outcrops on land were also examined.The diver used the following equipmentfor the underwater investigation:  \nI)Rubber dress,belt with lead weights,and fins.  \n2)Aga-Divator compressed-air unit(Fig.I).  \n3)Specially designed harness for towing (Fig.3).  \n4)Tow and life-line.  \n5)Sextant(Fig.5).  \nFig.I.Installation of air cylinders.Photo P.H.Lundegardh 1955.  \nThis equipment and various other items were borrowed from the Royal SwedishNavy.AB Iggesunds Bruk kindly lent the tug\"Dellen\",a raft,an air compressorpersonnel.  \nThe diver descended from the raft(II×6m.with cabin,Fig.2),on which theequipment could be stored during the night.The compressor(Atlas Diesel rock-drilling compressor,7 kg/sq.cm.)was mounted on the stern of the raft.The exhaust  \n十—561907.S.G.U.Ser.C.N:0548,Redaelli.  \ngases were led away through a 3-m.long pipe in order to prevent carbon monoxidefrom mixing with the intake air and being breathed by the diver.The raft waschained to the side of the\"Dellen\"and thus the tug could rapidly slow down andreverse the raft.However,the raft and tug tended to rotate,which made it difficultto use the sextant,as described below.  \n# The Physiological Aspects of Diving\n\nThe procedure followed consists of two distinct methods which are dependenton the physiological effects of diving.  \na)From the surface down to a depth of about Io m.a diver can operate freelyfor an unlimited l","cbCairdGlHfcxDQv","https://ap.wps.com/l/cbCairdGlHfcxDQv","pdf",17648207,24,"English","# Introduction\n## The physiological aspects of diving\n## Procedure\n## Conclusions regarding procedure\n## General remarks on Lake Norra Dellen\n## Topographical description\n## Geological and petrographic description\n## Description of rocks","[{\"question\":\"What was the main goal of the underwater investigation in Lake Norra Dellen?\",\"answer\":\"To apply geologic research methods—surveying and taking specimens—to an underwater region, focusing on the Dellen andesite and mapping the lake bed.\"},{\"question\":\"Why is staged ascent important during deep diving?\",\"answer\":\"At depths around 10–40/50 m, nitrogen dissolves in the blood in larger quantities; a rapid ascent can cause decompression sickness, which is avoided by ascending in stages and pausing for decompression.\"},{\"question\":\"What physiological limitation can occur at depths greater than about 30–50 m?\",\"answer\":\"Nitrogen narcosis, which can cause an intoxication-like effect, altered sensations of air, reduced work ability, and impaired judgment; the paper notes this can be mitigated by using other gas mixtures such as oxygen and helium.\"}]","A Petrological Investigation in Lake Norra Dellen - Preface and Introduction | PDF"]