diff --git a/modules/rntuple.mjs b/modules/rntuple.mjs
index a50d611f3..3584ad6ca 100644
--- a/modules/rntuple.mjs
+++ b/modules/rntuple.mjs
@@ -158,6 +158,7 @@ function getTypeByteSize(coltype) {
         case ENTupleColumnType.kSplitInt64:
         case ENTupleColumnType.kSplitUInt64:
         case ENTupleColumnType.kSplitReal64:
+        case ENTupleColumnType.kSplitIndex64:
             return 8;
 
         case ENTupleColumnType.kReal32:
@@ -168,7 +169,6 @@ function getTypeByteSize(coltype) {
         case ENTupleColumnType.kSplitUInt32:
         case ENTupleColumnType.kSplitReal32:
         case ENTupleColumnType.kSplitIndex32:
-        case ENTupleColumnType.kSplitIndex64:
             return 4;
         case ENTupleColumnType.kInt16:
         case ENTupleColumnType.kUInt16:
@@ -198,7 +198,9 @@ function recontructUnsplitBuffer(blob, columnDescriptor) {
         coltype === ENTupleColumnType.kSplitUInt64 ||
         coltype === ENTupleColumnType.kSplitReal16 ||
         coltype === ENTupleColumnType.kSplitReal32 ||
-        coltype === ENTupleColumnType.kSplitReal64
+        coltype === ENTupleColumnType.kSplitReal64 ||
+        coltype === ENTupleColumnType.kSplitIndex32 ||
+        coltype === ENTupleColumnType.kSplitIndex64
     ) {
         const byteSize = getTypeByteSize(coltype),
               splitView = new DataView(blob.buffer, blob.byteOffset, blob.byteLength),
@@ -255,6 +257,29 @@ function recontructUnsplitBuffer(blob, columnDescriptor) {
 }
 
 
+/**
+ * @summary Decode a reconstructed index buffer (32- or 64-bit deltas to absolute indices)
+ */
+function DecodeDeltaIndex(blob, coltype) {
+  let deltas, result;
+
+  if (coltype === ENTupleColumnType.kIndex32) {
+    deltas = new Int32Array(blob.buffer || blob, blob.byteOffset || 0, blob.byteLength / 4);
+    result = new Int32Array(deltas.length);
+  } else if (coltype === ENTupleColumnType.kIndex64) {
+    deltas = new BigInt64Array(blob.buffer || blob, blob.byteOffset || 0, blob.byteLength / 8);
+    result = new BigInt64Array(deltas.length);
+  } else
+    throw new Error(`DecodeDeltaIndex: unsupported column type ${coltype}`);
+
+  if (deltas.length > 0) result[0] = deltas[0];
+  for (let i = 1; i < deltas.length; ++i)
+    result[i] = result[i - 1] + deltas[i];
+
+  return { blob: result, coltype };
+}
+
+
 // Envelope Types
 // TODO: Define usage logic for envelope types in future
 // const kEnvelopeTypeHeader = 0x01,
@@ -686,13 +711,20 @@ class RNTupleDescriptorBuilder {
 
     // Example Of Deserializing Page Content
     deserializePage(blob, columnDescriptor) {
-        const {
-            blob: processedBlob,
-            coltype
-        } = recontructUnsplitBuffer(blob, columnDescriptor),
-            byteSize = getTypeByteSize(coltype),
-            reader = new RBufferReader(processedBlob),
-            values = [];
+        const originalColtype = columnDescriptor.coltype,
+        { coltype } = recontructUnsplitBuffer(blob, columnDescriptor);
+        let { blob: processedBlob } = recontructUnsplitBuffer(blob, columnDescriptor);
+
+        
+        // Handle split index types
+        if (originalColtype === ENTupleColumnType.kSplitIndex32 || originalColtype=== ENTupleColumnType.kSplitIndex64) {
+            const { blob: decodedArray } = DecodeDeltaIndex(processedBlob, coltype);
+            processedBlob = decodedArray;  
+        }
+
+        const byteSize = getTypeByteSize(coltype),
+              reader = new RBufferReader(processedBlob),
+              values = [];
 
         if (!byteSize)
             throw new Error('Invalid or unsupported column type: cannot determine byte size');
@@ -710,20 +742,19 @@ class RNTupleDescriptorBuilder {
                     val = reader.readF32();
                     break;
                 case ENTupleColumnType.kInt64:
-                    val = reader.readI64();
+                    val = reader.readS64();
                     break;
                 case ENTupleColumnType.kUInt64:
                     val = reader.readU64();
                     break;
                 case ENTupleColumnType.kInt32:
-                case ENTupleColumnType.kIndex32:
-                    val = reader.readU32();
+                    val = reader.readS32();
                     break;
                 case ENTupleColumnType.kUInt32:
                     val = reader.readU32();
                     break;
                 case ENTupleColumnType.kInt16:
-                    val = reader.readI16();
+                    val = reader.readS16();
                     break;
                 case ENTupleColumnType.kUInt16:
                     val = reader.readU16();
@@ -733,18 +764,16 @@ class RNTupleDescriptorBuilder {
                     break;
                 case ENTupleColumnType.kUInt8:
                 case ENTupleColumnType.kByte:
-                case ENTupleColumnType.kByteArray:
-                case ENTupleColumnType.kIndexArrayU8:
                     val = reader.readU8();
                     break;
                 case ENTupleColumnType.kChar:
                     val = String.fromCharCode(reader.readS8());
                     break;
-                case ENTupleColumnType.kIndex64:
-                    val = reader.readU64();
+                case ENTupleColumnType.kIndex32:
+                    val = reader.readS32();
                     break;
-                case ENTupleColumnType.kSplitIndex64:
-                    val = reader.readU32();
+                case ENTupleColumnType.kIndex64:
+                    val = reader.readS64();
                     break;
                 default:
                     throw new Error(`Unsupported column type: ${columnDescriptor.coltype}`);
@@ -954,7 +983,12 @@ function readNextCluster(rntuple, selector) {
 
                 // splitting string fields into offset and payload components
                 if (field.typeName === 'std::string') {
-                    if (colDesc.coltype === ENTupleColumnType.kIndex64) // Index64/Index32
+                    if (
+                         colDesc.coltype === ENTupleColumnType.kIndex64 ||
+                         colDesc.coltype === ENTupleColumnType.kIndex32 ||
+                         colDesc.coltype === ENTupleColumnType.kSplitIndex64 ||
+                         colDesc.coltype === ENTupleColumnType.kSplitIndex32
+                        ) // Index64/Index32
                         rntuple._clusterData[field.fieldName][0] = values; // Offsets
                     else if (colDesc.coltype === ENTupleColumnType.kChar)
                         rntuple._clusterData[field.fieldName][1] = values; // Payload