Bulletin No. 270 . Series B, Descriptive Geology, 73 DEPARTMENT OF THE INTERIOR UNITED STATES GEOLOGICAL SURVEY CHARLES D. VVALCOTT, DIHECTOK THE CONFIGURATION OF THE ROCK FLOOR OF GREATER NEW YORK BY WILLIAM HERBERT HOBBS WASHINGTON GOVERNMENT. PRINTING OFFICE 1905 CONTENTS. Page. LETTER OF TRANSMITTAL .................................................. 7 PART I. STRUCTURAL STUDIES ............................................. .9 Introduction......................................................... 9 Aids to geological studies on Manhattan Island..................... 9 Engineering enterprises that have pierced the rock floor............ 10 Keview of structural geological studies of the New York City area.... 12 Boroughs of Manhattan and the Bronx ........................ 12 Gale .................................................... 12 Mather.................................................. 12 Cozzens ................................................. 12 Stevens.................................................. 12 Credner................................................. 13 Newberry ............................................... 13 Dana.................................................... 14 Russell.................................................. 14 Kemp ................................................... 14 Merrill .................................................. 15 Eckel ................................................... 16 Gratacap ................................................ '16 Julien ..................... i.............................. 17 Peet..................................................... 19 Hobbs .................................................. 19 Area west of the Hudson...................................... 19 Comment.................................................... 20 Scope of the present study .................................... 20 Form of the rock pedestal of Manhattan ............................... 21 Exposed portion of the rock basement............................. 21 Covered portion of the basement .................................. 22 Transverse sections of the island....... -. ................ : .......... 25 Longitudinal sections of the island................................. 26 Along Broadway from the Battery to 33d street ................ 26 Along Lenox and Westchester avenues from 96th street to Mel- rose avenue................................................ 27 Along Broadway and Eleventh avenue between 72d and Dyck- man streets ................................................ 29 PART II. BORINGS MADE IN NEW YORK AND VICINITY .................... 30 Borings beneath channels on water front............................... 30 East River front.................................................. 30 Dock and bulkhead lines......:.....,......................... 30 Miscellaneous......... ......................................i. 31. 4 CONTENTS. PART II. BOEINGS MADE IN NEW YORK AND VICINITY Continued. Page- Borings beneath channels on water front Continued. East River sections............................................... 32 East River Gas Company's tunnel............................. 32 Bridges NOB. 2, 3, and 4 ...................................... 32 East River reefs.............................................. 34 Center line of 42d street (produced) ........................... 34 Pennsylvania Railroad tunnel................................. 34 New York-Brooklyn tunnel of rapid, transit commission ........ 35 Hudson River front.............................................. 36 Dock, bulkhead, and pier lines. ............................... 36 Miscellaneous. ................................................ 38 Hudson River sections..............................'.............. 40 Reef one-fourth mile from pier A.............................. 40 Bedloe Island................................................. 40 McAdoo tunnel .............................................". 40 Pennsylvania, New York and Long Island Railroad tunnel...... 40 Proposed bridge at 59th street................................. 41 Harlem River front and sections .................................. 41 Spuyten Duyvil Bridge ....................................... 41 Dock line.................................................... 41 Washington and High bridges ................................ 42 New aqueduct.................................................. 42 Macomb's dam, Central Bridge...............................'. 43 Line 400 feet east of Central Bridge. ............................ 43 New York Central and 145th street bridges .................... 43 Rapid-transit tunnel......................'.................... 43 Madison, Park, Third, Second, and Willis avenue bridges....... 44 Borings in the Borough of Manhattan................................... 44 Line of subway .................................................. 44 On or near Broadway......................... '................ 44 On Lexington avenue, 110th street, and 34th street............. 45 Profile along Broadway............................................. 49 Foundations of tall buildings......................... ............ 51 Lines of 31st, 32d, 33d, and 34th streets............................ 55 Along Fourth avenue....................... 1 ..... ^..^............ 58 Riverside Park extension ......................................... 59 Riverside and Manhattan viaducts and Tenth avenue............... 66 Records from miscellaneous sources ............................... 67 Borings in the outlying boroughs arid in other localities near New York.. 83 Borough of Brooklyn............................................. 83 Borough of Queens.....'............:...........................-.. .86 Borough of the Bronx ............................................ 87 Adjacent points in New Jersey and elsewhere .....'................. -89 INDEX ....................'............................................... 95 ILLUSTRATIONS. Page. PLATE. I. Map of the southern portion of Manhattan Island, with portions of the Long Island and New Jersey shores, showing the configuration of the rock floor............................................... 20 II. Map of northern and eastern portions of Manhattan Island, showing the configuration of the rock floor............................... 22 III. Sketch map of Manhattan Island, showing the location of some of the river sections .................................'................ 24 IV. Series of profiles across the Harlem River, showing the position and configuration of the rock surface ............................... 26 V. Section of the rock basement of Manhattan along the line of Broad­ way from the Battery to 33d street............................. 28 FIG. 1. Rock surface beneath the new Stock Exchange building, between New and Broad streets ............................................... 11 2. Sketch map of Manhattan Island (after Kerap)..................... 15 3. Sketch map of Manhattan Island, showing location of special transverse and longitudinal sections ........................................ 24 4. Transverse sections across Manhattan Island between 31st and 34th streets.. ....................................................... 25 5. Section along Lenox and AVestchester avenues from 96th street, Man­ hattan, to Melrose avenue, Bronx................................ 28 6. Section along Broadway and Eleventh avenue from 72d street to Dyck- rnan street....................................................... 28 LETTER OF TRANSMITTAL. DEPARTMENT or THE INTERIOR, UNITED STATICS GEOLOGICAL SURVEY, Washington, D. 0., February 14, 1905. SIR: I transmit herewith the manuscript of a report on "The Con­ figuration of the Rock Floor of Greater New York," by William H. Hobbs, and recommend its publication as a1 bulletin. The report contains a large amount of geological information of the highest importance to engineers engaged in construction work in New York involving excavations for foundations and other purposes. The facts are presented by both verbal and graphic means in such a man­ ner as to be most useful to the engineer, and at the same time to be nighty suggestive and valuable to the student of geolog}^. Very respectfully, C. W. HAYES, Geologist in Charge of Geology. Hon. CHARLES D. WALCOTT, Director United States Geological Survey. CONFIGURATION. OF THE ROCK FLOOR OF GREATER NEW YORK. By WILLIAM H. HOBBS. ' PART I.-STRUCTURAL STUDIES. INTRODUCTION. AIDS TO GEOLOGICAL STUDIES ON MANHATTAN ISLAND. Accurate maps.-. The ear^y importance of Manhattan Island in com­ mercial and economic lines and its entry upon great engineering' enter­ prises which require a penetration of the rock floor have greatly facilitated the work of the structural geologist within the area. As early as 1821 the city was laid out, and the gridiron of numbered streets and avenues has not only .been responsible for a precision and accuracy of the early maps, rarely obtainable elsewhere, but has given to even casual geological observations unusual value. Tftandall's map of the island, submitted in sections between the years 1811 and 1821, now preserved in the office of the commissioner of public works, gives the precise locations of all the old farms in relation to watercourses and topography. .It comprises four volumes of 92 sheets of map, size 25 by 37 inches, on scale of 100 feet to the inch. General Viele's map, on the scale of 1,000 feet to the inch,.was published in 1874," and is based upon Randall's map. It shows the original shore line of the island, the