DOCUMENTING SAND AND GRAVEL RESOURCES ON THE INNER CONTINENTAL SHELF: MERRIMACK EMBAYMENT, NEW ENGLAND A report for: United States Minerals Management Service Duncan M. FitzGerald Christopher J. Hein Department of Earth Sciences Boston University Boston, MA 02215 JULY 2009 TABLE OF CONTENTS EXECUTIVE SUMMARY . 1 INTRODUCTION . 2 Work Statement . 2 Previous Work . 3 Objectives & Scientific Questions . 3 PHYSICAL SETTING . 5 Modern Physical Setting . 5 Sea Level History . 7 Formation of Lowstand Paleodelta . 8 Holocene Transgression and Sediment Reworking . 10 DATA ACQUISITION . 12 Mapping . 12 Bathymetry . 13 Backscatter Surveys . 14 Shallow Seismic Surveys . 15 Bottom Sampling . 16 Instrument Deployment . 20 RESULTS . 24 Surficial Sediment Classification of the Merrimack Embayment . 24 Surficial Geologic Map . 31 Evidence of Modern Reworking . 33 Analysis of Instrument Deployment Data . 36 Shallow Seismic Analysis . 39 Litho- and Microbiofacies Maps Defining Sedimentary Environments . 41 DISCUSSION . 42 Overview . 42 Pleistocene Braid Plain Deposits . 44 Holocene Mobile Sand Sheet . 46 Impact of Sediment Removal from Borrow Site . 46 SUMMARY AND CONCLUSIONS . 50 The Merrimack Braid Plain Delta and the Lowstand Paleodelta. 50 The Holocene Transgression and Reworking of Paleodelta & MBPD Sediments . 50 Present Day Processes & Impact of Sediment Removal . 51 REFERENCES . 52 i LIST OF FIGURES Figure 1 – Location Map of Merrimack Embayment . 5 Figure 2 – Wave Data from Merrimack Embayment . 6 Figure 3 – Massachusetts Relative Sea Level Curve . 8 Figure 4 – Location of Merrimack Paleodelta . 6 Figure 5 – Tracklines Map . 12 Figure 6 – Bathymetric Map . 13 Figure 7 – Backscatter Map . 14 Figure 8 – Shallow Seismic Tracklines . 16 Figure 9 – Bottom Grab Samples Map . 17 Figure 10 – University of New Hampshire Bottom Sample Map . 18 Figure 11 – Sediment Photos . 19 Figure 12 – Instrument Deployment Site . 20 Figure 13 – Instrument Tripod . 22 Figure 14 – Bottom Samples Classified by Mean Grain Size . 24 Figure 15 – Bottom Samples Classified by Sorting . 25 Figure 16 – Bottom Samples Classified by Dominant Sediment Type . 26 Figure 16a – Percent Clay . 26 Figure 16b – Percent Silt . 27 Figure 16c – Percent Sand . 28 Figure 16d – Percent Gravel . 29 Figure 17 – Sea Floor Regions Mapped by Backscatter . 30 Figure 18 – Bedform Field Map . 34 Figure 19 – Pressure and Current Deployment Time Series . 36 Figure 20 – Wave Deployment Time Series . 37 Figure 21 – Sample Interpreted Shallow Seismic Line . 39 Figure 22 – Map of Cut & Fill Features . 40 Figure 23 – Barrier Island Grain Size Trends . 43 Figure 24 – SWAN Model Target Region . 47 Figure 25 – SWAN Model Results After Removal of 5 m of Sediment . 48 Figure 26 – SWAN Model Results After Removal of 2 m of Sediment. 49 ii LIST OF TABLES Table 1.